Depth of Field, Hyperfocal Distance, Infinity, and Beyond! (Podcast 732)

Depth of Field, Hyperfocal Distance, Infinity, and Beyond! (Podcast 732)


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Today we’re going to look at both Depth of Field and his cousin Hyperfocal Distance, and take this to Infinity and Beyond in one post. I’ve covered Depth of Field and Hyperfocal Distance a number of times in different posts, but an update that I just completed for my iOS app Photographer’s Friend introduces a new concept related to Infinity, so I figured I’ll pull all of this into one post that will hopefully be all you need to reference to get a good understanding of these theories. We’ll start with the basics, and then geek out a little with some of the calculations, and then move on to some examples to illustrate why keeping your eye on your depth of field is important.

What is Depth of Field?

Let’s start with an explanation of Depth of Field, which is the area of a photograph that is in focus at any given setting. The depth of field is affected by a number of factors. On your camera, the setting that affects Depth of Field the most is your aperture. Wide apertures like ƒ/2.8 or ƒ/4 have a shallow depth of field, where not much is in focus, and smaller apertures, like ƒ/16 and ƒ/22, have very deep depth of field with a lot of the image in focus.

The other main parameters that affect the depth of field are your focal length and focus distance. Wide focal lengths like 24mm have more depth of field and longer focal lengths like 100mm have less depth of field, so the more you zoom, the shallower your depth of field gets. And the closer you focus, the shallower your depth of field gets as well. Let’s note too that when using smaller apertures at close range, in general, depth of field extends on third towards your camera from the point at which you are focused, and two-thirds back. The far focus limit extends out more as you approach hyperfocal distance, but we’ll talk about that shortly. For example, say you focus a 50mm lens with the aperture set to ƒ/8 at 18 feet or 5.5 meters, the near limit of the focus would be at 11 feet or 3.4 meters, and the far limit of the focus would be at 29 feet or 9 meters. So approximately one-third in front of your subject and two-thirds behind.

Depth of Field Near and Far Limits
Depth of Field Near and Far Limits

Keep in mind that the focus doesn’t just switch abruptly from being sharp to not being sharp. The point at which you focus your lens is the sharpest image that your lens and camera can resolve, and the image gets gradually softer as you move away from this point. The depth of field is the area that we would consider acceptably sharp, and it is a gradual defocussing of the image to the point where we would consider it no longer acceptably sharp, and these are the near and far limits of the depth of field.

Long-time followers might recall the following six diagrams showing the mechanism of depth of field at different focal lengths and focus distances. It’s important to understand the relationship between aperture, focal length, and focus distance before we go on, so while trying not to go into too much detail, let’s outline what I’ve covered in these diagrams. Diagram #1 shows the depth of field with a 50mm lens with the aperture set at ƒ/2.8 and focussed at 2 meters or 6.6 feet. Because the aperture is wide at ƒ/2.8 the light is focussed at a more acute angle, between the two widest points of the aperture. This means that the circle made by the light as it passes through the aperture reaches a point where it is no longer acceptably sharp quite quickly. You can see that the near limit is just 1.9 meters or 6.2 feet and the far limit is 2.1 meters or 7 feet. The total depth of field is just 27 cm or just under one foot.

In Diagram #2 we stop the aperture down to ƒ/5.6 at the same distance and the depth of field increases to 54 cm or 1.8 feet. This is just because the angle of the light passing through the aperture is now less acute. In Diagram #3 with an aperture of ƒ/11 the depth of field increases to 1.14 meters or 3.8 feet at the same focus distance, once again, because the light is passing through a smaller aperture and therefore the circle of acceptable sharpness is reached much further away from the point at which the lens was focussed. All three of these diagrams were assuming a 50mm lens focussed at 2 meters or 6.6 feet.

In Diagram #4 we take the same 50mm lens and this time focus it at 5 meters or 16.4 feet with an aperture of ƒ/5.6 and we now get a depth of field of 3.8 meters or 12.5 feet so by increasing the focus distance from 2 to 5 meters or 6.6 to 16.4 feet our depth of field is almost eight times deeper at the same aperture. Again, this is because focussing further away gives us a shallower angle of the light, so the circles of acceptable focus are further away from each other.

Conversely, in Diagram #5 we focus closer to the lens, still with an aperture of ƒ/5.6 and see that the angle of the light is much more acute and the acceptable focus circles are close together, giving us a depth of field of just 3cm or just over an inch. And the final diagram shows the angle being more acute still as the light passes through a wider aperture of ƒ/2.8 for just 2cm or 3/4 of an inch depth of field. If any part of this was new to you, I hope it’s relatively easy to understand how depth of field is affected by the aperture and focus distance. I’ll share a formula shortly that will help you to understand the relationship with the focal length as well, but before that, let’s talk about Hyperfocal Distance.

Hyperfocal Distance

For any given focal length and aperture combination, there is a point at which the far limit of the depth of field is so far away that everything after the near limit of your depth of field can be considered acceptably sharp, and this is what’s known as the Hyperfocal Distance. Here is a diagram that I created to illustrate this back in 2013, although you may see this stolen and illegally rebranded on other sites, and you can see that for a 24 mm lens at an aperture of ƒ/16 the hyperfocal distance is much closer than with a 50 mm lens, and much closer still than a lens set to a focal length of 200 mm.

Hyperfocal Distance Diagram
Hyperfocal Distance Diagram

You’ll see that I’ve added a note which reads: Although still a good reference point, note that the calculations on this diagram are based on the somewhat outdated traditional depth of field calculations which assume the photograph has been printed at 8 x 10 inches and is being viewed at arm’s length. I’ll explain more about why this might be something you need to be concerned about shortly, but these numbers are still a good standard to help talk about the theory, and before we jump further down the rabbit hole, there is another part to all of this that we’ve already touched on but need to cover the terminology first, and that is the Circle of Confusion.

The Circle of Confusion

Until now I’ve been calling it the circle of acceptable focus, to avoid ‘confusion’ but in optical physics, it’s known as the Circle of Confusion. In terms of focus, this is the limit that the light rays can spread out but still appear to be in focus. In this diagram from a post an older post, you can see that I have included light from the near and far focus limits, and tried to show how it gets gradually more blurry as we move away from the critical focus point, which is light coming from the point at which we focussed the lens.

Circle of Confusion Diagram
Circle of Confusion Diagram

The reason that the Circle of Confusion is important to this topic is that it is required to calculate Hyperfocal Distance. The calculation is actually not very difficult, so let’s go over that quickly before we move on. First here is the formula with words rather than numbers. So we have Focal Length to the power of two over the Aperture multiplied by the Circle of Confusion. This gives us the Hyperfocal Distance.

\frac {focal\hspace{2mm}length^{2}} {aperture \hspace{2mm} \times \hspace{2mm} Circle\hspace{2mm}of\hspace{2mm}Confusion} = {hyperfocal \hspace{1mm} distance}

If we replace the words with some real numbers now, we’d do, for example, 24 to the power of two over 16 multiplied by 0.030, which gives us 1200. This is 1.2 meters, which is the distance I had in my earlier diagram for hyperfocal distance. This assumes a circle of confusion of 0.030 millimeters or 30 µm (microns or micrometers) which is a commonly used circle of confusion for 35mm sensors.

\frac {24^{2}} {16\times0.030} = {1200}

So, this brings us up to speed on the theory behind Hyperfocal Distance and Depth of Field is calculated from the Hyperfocal Distance, but it’s considerably more complicated, so we won’t go into that much detail today, as the main reason for the inaccuracy of the traditional calculation is the circle of confusion, which we are now up to speed on,

Why is the Traditional Depth of Field Calculation Outdated?

As I mentioned, the traditional Depth of Field calculation based on evaluating sharpness in an 8 x 10 inch print at arm’s length, is outdated because unfortunately, more than 99% of images that are created today are never printed, so it’s really only useful as a standard to discuss the theory. Most people check focus on the computer screen, and most of the time, we check by zooming in to 100% at a point where it is important for the image to be in focus. It’s fashionable to dismiss this kind of evaluation as being too picky, but in the dark corners of our studies, hotel rooms, or basements, I know that people do this. It’s human nature to want the best for our creations, so before we really commit to liking a shot, we have to know that it’s sharp and will bear up to a certain level of scrutiny. Seriously though, if, for example, you are going to print your work out large or display it on a big screen, you have to check that it is sharp unless you did not intend it to be.

Pixel Peeper Mode

This is why I developed Pixel Peeper Mode for the Depth of Field calculator in my Photographer’s Friend app. When you enable Pixel Peeper mode we calculate the pixel pitch of your sensor based on the sensor format that you select on the main calculator screen and the number of megapixels that you select on the settings screen. I’ve outlined both of these here for anyone that uses Photographer’s Friend. I’ve included two more screenshots to the right though, to illustrate this point and to help with understanding this concept.

Pixel Peeper Mode Examples
Pixel Peeper Mode ExamplesI

The screenshot on the left shows both the Pixel Peeper Mode switch being turned on, and that I have selected the megapixels for my camera, which is the 45 megapixel Canon EOS R5. You will, of course, select whatever the megapixel count is for your own camera. Then on the main calculator screen, select your camera’s sensor format, which in my case is 35mm full-frame. If you use a crop factor camera select the correct ratio, such as CF1.6, 1.5, or 1.3, etc. The larger crop factors are actually for sub-medium format sensors and there are also sizes for medium and some large format sensor and film sizes to choose from.

The important thing with regards to depth of field here though can be seen on the two screenshots on the right side. Notice how the Hyperfocal Distance and the Hyperfocal Depth of Field readouts change when we have Pixel Peeper Mode turned on compared to when it’s off. The Hyperfocal Distance changes from 1.26 meters to 3.3 meters, which is 4.15 to 10.9 feet. Under the Hyperfocal DoF section, you can see that with Pixel Peeper mode turned off, we’re looking at the depth of field starting at 63 cm or 2 feet and extending out to infinity, which we will also talk about shortly. With Pixel Peeper Mode turned on, that increases significantly to 5.5 feet or 1.65 meters.

You may be wondering why the non-Pixel Peeper mode number is not 1.2 meters, as we saw in earlier calculations. This is because even without Pixel Peeper mode I am using a slightly smaller circle of confusion, rounded to 29 µm, as this is more accurate than 30 µm used before, and that gives us slightly longer distances. Notice though that when Pixel Peeper is turned on, the CoC label above the Format dial now shows 11 µm for the Circle of Confusion, which is much smaller. This is calculated from the sensor size and the megapixels, which enables me to calculate the Pixel Pitch, which in turn enables me to calculate the Circle of Confusion.

Airy Disk Pattern
Airy Disk Pattern

The Airy Pattern

There is actually another somewhat obscure piece to the overall puzzle that we should touch on to really make this post cover everything you need to know about depth of field, and that is the Airy Pattern or Airy Disk. With the understanding that we get greater depth of field as we make our aperture smaller, you’d think that when you want more of your scene to be sharper, you could just select a really small aperture. Many lenses for 35mm format cameras go down to f/22 and sometimes f/32 or smaller, and medium and large format lenses often go to much smaller apertures to get enough depth of field. 

But, as good as the manufacturers make our lenses, there is a phenomenon that occurs as light passes through a very small aperture that causes problems. As light passes through a wide aperture, it makes its way to the sensor or film relatively undisturbed, but as light passes through a small aperture, it interferes with other rays of light, causing it to spread out. The result is what’s known as diffraction and to explain that, we need to talk about the  “Airy Pattern” (right) with a central “Airy Disk”, both named after George Airy, the person who discovered this phenomenon.

Airy Patterns
Airy Patterns

As you can see from the mockup of the Airy Disk on the right, there is a central core of light which makes up about 84% of the light, and then a number of concentric rings. While there is still a gap between the central core or Airy Disk, and the next Airy Disk, the light is said to be “well resolved”. According to the Rayleigh Criterion, the dots are “just resolved” if the center of the first Airy Pattern is superimposed on the first dark ring of the second pattern. When two airy disks become closer than half their width, the light is considered not resolved. This is when you will see diffraction cause everything in your image to be slightly out of focus at small apertures.

Color-Coded Diffraction Warnings

Based on this and the information I already calculated in Photographer’s Friend, I am able to calculate the Diffraction Limits and this is what enables me to provide Color-Coded Diffraction Warnings. The AD label which shows the size of the Airy Disk and the Aperture Dial are color-coded to show the risk of Diffraction as you adjust the aperture dial. If you don’t see this, turn these options on in the Depth of Field Calculator settings.

Because the Circle of Confusion size is rather large in the traditional 8 x 10-inch print calculation method, you actually need to start being concerned when the Airy Disk gets to around 80% of the size of the Circle of Confusion. So, when you are not in Pixel Peeper mode, the color of the Aperture dial will change from green to amber when the Airy Disk passes 80% of the default Circle of Confusion size, and for 35mm format, that is around an aperture of f/18. It then goes red from 100%, which is f/22 at the default settings. This matches my own test results.

In Pixel Peeper mode, these boundaries are a little more conservative, but I set amber to kick in when the Airy Disk reaches the same size as the Circle of Confusion and then the red Diffraction Limit warning when the Airy Disk is twice the size of the Circle of Confusion. These parameters cause the dial to go amber from f/10 for a 35mm format camera at 30 megapixels, and then turn red from f/20. 

Based on my own tests, I personally think that f/10 is a little too early, but the physics tells us that there is a possibility of seeing the effects of diffraction at this point, so that’s what we use, but consider this as intended, as an amber warning. Ideally, you’ll do your own tests to see when you start to see diffraction in your images and adjust your expectations accordingly. There are details of how to do diffraction tests in Episode 594, when I originally talked about this.

Diffraction Warnings
Diffraction Warnings

Infinity and Beyond!

As I mentioned earlier, I’m about to release an update to Photographer’s Friend which adds a number of new features, including translation into a number of new languages and some improvements to the user interface, but the relevance for this discussion comes in the form of a new Infinity slider on the Depth of Field Calculator Settings page. Because of the work involved in bringing you these features this slider is part of the Pro Add-on, which means you need to buy the Pro Add-on for this to be available, but if you already own the Pro Add-on, you’re good to go. What this slider does is allows you to set a custom distance for Infinity. You might initially think, well, infinity is infinity, why would I need to set it? But there are a few reasons why this might be useful, as I’ll explain.

Lens Infinity and Focus Infinity

I’m risking going down a rabbit hole by bringing this up at this point, as this took a lot of wrapping my own head around initially, but I think to ultimately avoid confusion, we should probably talk about the difference between the Infinity symbol that you see on your lenses and infinity in the context of the extent of focus in Depth of Field, because these are really not the same.

If you check your lenses you will see that what is considered Infinity looks slightly different, depending on the lens. For example, when I focus with my RF 15-35mm lens from Canon, in the viewfinder I see distance guides in meters which reads 0.28, 0.4, 0.6, 1, then the Infinity symbol, which, if you follow the spacing of the marked distances, seems to signify about 5 meters. My RF 50mm lens shows distances of 0.4, 0.5, 0.7, 1, 1.5, 3, then the infinity symbol, which in this case seems to signify around 10 meters. Finally, as a reference, my RF 100-500mm lens reads 0.9, 1.2, 1.6, 2, 3, 7, then the infinity symbol, and from my tests, focus stops increasing at around 40m.

When I initially developed this feature I added the ability to restrict Hyperfocal distance down to as little as 5 meters, or 16 feet, but I found it to be almost completely useless in this context. The reason for that is because the speed at which focus advances towards infinity is non-linear. After my 50 mm lens passes 3 meters when turning the focus ring at the same rate the speed at which focus moves towards infinity starts to increase much more rapidly. Although a quarter of a turn on the focus ring might take me from 1.5 to 3 meters, the following quarter-turn doesn’t take the lens from 3 meters to 4.5 meters. Rather, it takes the lens on a much steeper curve from 3 meters all the way to infinity, and that is really far!

Non-Linear Focus Curve
Non-Linear Focus Curve

As I researched these changes I found an old forum post where people were laying down the law about infinity by lens, some quoting infinity as being as close as 20 feet, but this assumes a linear increase in the focus and an abrupt stop after the last number of the focus dial or as in the case of my Canon mirrorless camera, the focus range displayed in the electronic viewfinder, as it’s no longer present on the barrel of the lenses. Another observation is that you can actually see the infinity calculations start to peak if you opt to display the calculated Infinity value that I’ll talk about in a moment. It was watching this peek that brought all of this home to me, and that is the reason that I’ve changed this functionality in Photographer’s Friend, because I know I’m not the only geek using it. I get excited when technology helps me to gain a deeper understanding of the world around me, and I wanted to share that.

No More Limits!

Until now, when displaying Infinity in Photographer’s Friend I have simply used 1000 meters as a generic cut-off, and although we showed the infinity symbol for the depth of field, as the distance went past 1000 meters we just showed greater than “>1000 m” and that doesn’t provide the information that feeds my curiosity. So from version 3.7 of Photographer’s Friend which should be available in the App Store in the coming days, whether you own the Pro Add-on or not, you will be able to tap the Depth of Field label or the Far Limit label and cycle through three different infinity display modes.

The default mode displays the preset infinity value in parentheses, which will remain at 1000 meters and display as “>∞ (1 km)” or “>∞ (0.6 mi)”. With the Pro Add-on, the distance will change to whatever you set it to with the Infinity slider on the settings page. The second mode will just show the greater than symbol and infinity symbol “>∞” when the distance is greater than infinity. This really just gives you the option to clean up the interface, making it less cluttered when necessary. The third mode is the geeky one, which shows the calculated distance as it races towards infinity, which actually can extend out way past the originally used 1000 meter limit, so for long focal lengths, you may see something like “>∞ 57 km” or “>∞ 36 mi”. The calculated distances increase very rapidly for wide-angle lenses, so it’s harder to see the gradual increase because of the distance steps, but if you change to a longer focal length like 500mm, you can actually watch the focus increase faster and faster as it heads towards infinity, and I personally find that fascinating.

Once we hit true infinity, the depth of field calculation actually returns a negative number, so I have to convert that to a large positive number, so at that point, I have no choice but to show an Infinity symbol as we really are at infinity.

By adjusting the preset Infinity value with the new slider in the Depth of Field Calculator settings, you are giving yourself more reference points as you shoot. Because of the non-linear nature of the focus advance towards infinity, I don’t recommend trying to use something like 20 feet or a really close number that you might find online, but I have made the slider start at 50 meters or 164 feet, which I feel is close enough to be useful, and it extends out to one mile or just over 1600 meters. You use this to get a reminder of when a wider angle lens is theoretically approaching infinity, because the readout labels for Far Limit and Depth of Field will change color, and you can select any three of the modes I discussed earlier, whichever you find most useful. Personally, I’m enjoying seeing the colored label and infinity symbol kick in, but I’m working mostly with mode three, which shows the actually calculated infinity distance, so you get the best of both worlds.

For example, in this screenshot, I have Infinity set to 100m which will put you at 330 feet if you hit the new measurement unit toggle switch that I also just added, or tap the distance dial label. The focus distance is set to 75 meters, which not greater than the calculated Hyperfocal Distance, but because I have the Infinity slider set to 100m I already have a colored label for the Far Limit and the greater than Infinity symbols in place because the far limit is passed the Infinity distance that I have preset, but I have an approximately equal symbol with the infinity symbol in the Depth of Field readout, to tell me that I’ve surpassed by preset Infinity distance, but it’s not yet greater than the calculated infinity distance. Basically, we can now use this as an indication that we’re approaching the calculated Infinity, and we can still monitor that we’re not quite at true infinity because of the approximation symbol.

Approximately Infinite
Approximately Infinite

Or, for example, here I have the focus distance dial past the Hyperfocal Distance and the Infinity display in mode 2, so I just get the greater than infinity symbols for a nice clean readout if that’s all I care about. How you use these features is completely up to you. I’m just providing the tools, and as is often the case with Photographer’s Friend, some uses are practical field techniques, and others are to help you get your head around the technical aspects of photography.

Infinity Symbols Hyperfocal Distance
Infinity Symbols Hyperfocal Distance

Why is Pixel Peeper Mode Important?

A young Himba lady caught in a moment of thought
A young Himba lady caught in a moment of thought

OK, so as we start to wrap this up, I’d like to talk a little about why it’s important to use Pixel Peeper Mode. In the past, I’ve spoken with people that had concerns about focus, and sometimes think there may have been a problem with their camera. Most of the time it turns out that the problems stemmed from a lack of information or full understanding of just how shallow depth of field gets with modern high-resolution cameras. Keep in mind that if you are going to check the focus in your images by making an 8 x 10-inch print and look at it at arm’s length, the traditional calculation is fine, but for larger prints and when checking your focus at 100%, especially on a large screen, your images won’t show as much depth of field as you would think based on the traditional calculations.

To illustrate this point though, take a look at this portrait of a young Himba girl from my Complete Namibia Tour. For this portrait, I used an aperture of ƒ/2.8 which will give us a reasonably shallow depth of field, although the lens would go as wide as ƒ/1.2. It’s tempting to shoot portraits wide open, and at times I do, but you have to understand just how shallow the depth of field is. With the traditional calculation, f/2.8 at a focal length of 50mm, and I see from my EXIF data that I was focussed at 65cm, learn that I have a depth of field of 2.5 cm or one inch. That’s already quite shallow, but if I switch to Pixel Peeper mode, which calculates the actual depth of field for my 30 megapixels Canon EOS R at these settings, I find that I actually only have a depth of field of 1.172 cm which is slightly under a half of an inch.

Now, I like this look and it was intentional, but if you study the image you’ll see that only her right eye, mouth, and part of her headdress are crisply sharp. Everything else gradually gets softer as we move away from this shallow plane of focus, of just over 1 centimeter.

One person that I spoke to in the past said that they couldn’t get a sharp photograph with the Canon EOS 5Ds R, and they were shooting with an 85mm ƒ/1.2 lens wide open at a distance of around 5 feet or 1.5 meters, and they thought they should have a few centimeters of depth of field. With the traditional calculation at these settings, indeed, they would have just over 2 centimeters of depth of field, similar to what I had in this shot of the Himba girl. What they actually had was 7 mm, and when we inspected the images we could see that there was a very thin line of sharpness, rather than the image being completely out of focus as they’d thought.

This is why it is important, especially when working with very shallow depth of field, to understand just how much focus you can expect, and Pixel Peeper mode in my iOS app can provide you with this information simply by turning it on and selecting your sensor’s megapixels. If you don’t already own Photographer’s Friend, you can find it on the Apple App Store here, and there are more details about the Depth of Field and other calculators and features on the product page here.

Stopping Down for Wildlife

Another thing that comes up in conversation a lot is the necessity to stop down your aperture a little for large wildlife subjects. Sure, if you just want the eyes sharp, and yes, that can provide a beautiful look, then staying wide open is fine, but if, for example, you are photographing a large bird in flight, and want to see more of the wings sharp, stopping down a little is important. For example, this Steller’s Sea Eagle shot at 16 meters or 52 feet has a wingspan of around 2.5 meters, just over 8 feet. Even with the wings folded slightly like this, we’re still talking about almost 2 meters from tip to tip. At ƒ/10 with a focal length of 400mm, my depth of field with the traditional calculation is 90 cm or just under 3 feet, but with a 30-megapixel camera, we’re actually looking at less than half that, at 42 cm or 16 inches. Now, I don’t mind the wing tips being out of focus like this, but the amount you see in this photo is based on my selected aperture of ƒ/10. If I’d shot this wide open, there would have been much less focus on the near edge of the wings, and it probably would have bugged the hell out of me.

For this Crane shot, when there were two subjects, I was focussing at a distance of 35 meters or 110 feet, with a focal length of 700mm, and with the traditional calculation I should have around 1.5 meters or almost 5 feet of depth of field, which would probably have been enough to get both birds sharp, but for a 30-megapixel camera, which is what I was using, in Pixel Peeper mode, I see that I actually only had 68 cm or 26 inches. The result is that the second of the two Red-Crowned Cranes is slightly out of focus, even at ƒ/11. I actually often stop down to ƒ/14 when there are multiple subjects, but didn’t on this occasion, and the results are, to me at least, a little bit disappointing.

Hyperfocal Distance Use in Landscape Photography

Finally, I’d like to mention that when doing landscape photography I actually rarely photograph using Hyperfocal distance. The theory is that if you identify the Hyperfocal distance and then focus at that point, you can ensure that everything from the near limit of your depth of field to infinity will be in focus. With relatively wide-angle lenses though, the depth of field is deep enough that in general, if you focus around a third of the way into the frame, you will be approximately shooting at the Hyperfocal distance, and don’t really need to calculate it. I generally still just focus on the subject that is most important in the frame and from experience I generally know that this is going to give me sufficient depth of field. It’s important to note though that I built that experience by using tools like my Photographer’s Friend Depth of Field Calculator and checking the results of my work to ensure that my understanding of the limitations we face is accurate.

Landmannalaugar
Landmannalaugar

In this image of me looking out across the valley at Landmannalaugar in Iceland, I simply focussed on the rock on which I intended to stand, and everything from the foreground to the distant mountains is in focus because I had a focal length of 38mm and my aperture set to ƒ/16. I had focussed around 10 meters into the frame and the hyperfocal distance is around 8 meters, so everything from 4 meters to infinity was in focus.

When you use longer focal lengths, even for landscape, the depth of field does need to be considered more carefully, so I will sometimes reach for my calculator when using long focal lengths, even for landscape. I love that my Canon mirrorless cameras also now have a distance scale right there in the viewfinder so that I can see the distance at which I’m focusing when I do want to use Hyperfocal distance for maximum depth of field.

Just so that you know, it’s actually not a simple task to find the actual focus distance of an image just by looking at the EXIF data in your computer’s file browser, as few programs actually show this. I use a neat piece of software called RawDigger for this, which allows me to see what Canon interprets as the Near and Far focus limits, and that allows me to approximate my focus distance, so I just wanted to give that mention.

Out of Chicago Live!

I do hope you found this post useful. We’ll wrap it up there, but before we finish I’d like to mention that I will be teaching alongside the world’s best photographers at Out of Chicago LIVE! This will be running from April 9 to 11th, 2021, so SAVE THE DATE! You can find more information at www.outofchicago.com. I hope to see you there!

Out of Chicago LIVE! 2021
Out of Chicago LIVE! 2021

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Show Notes

See details of the Out of Chicago LIVE event here: https://www.outofchicago.com

And you can find RawDigger here: https://www.rawdigger.com

Music by Martin Bailey


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Capture One Pro Winner & Photographer’s Friend Sneak Peek (Podcast 706)

Capture One Pro Winner & Photographer’s Friend Sneak Peek (Podcast 706)


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My name is Martin and I’m a workaholic. Semi-seriously, I’m quite concerned by my inability to drag myself away from the development work that I’m doing on our Photographer’s Friend iOS app. It’s ruling my life and taking up my weekends, evenings, and pretty much every other waking minute, until something becomes so urgent that I have to walk away and take care of business. The Podcast is suffering too, because I’m not able to do anything outside of this coding, but I can’t promise to fix that straight away, as I have some more to do before I can relax a little.

I was doing silent screams at my desk every day last week as the evening drew near and I still hadn’t created this episode, in which I wanted to announce the winners of the free Capture One Pro license that I have to give away. We’ll get to that first today though, and then I will give you a sneak peak at what I’m doing with Photographer’s Friend, as there is some pretty cool stuff that is now mostly working, but the release format is still up in the air as I struggle with Apple’s In-App Purchases testing environment. Anyway, without any further ado, I’d like to announce the winner of Capture One Pro.

And the Winner Is…

I have dragged my feet on announcing the winner of the free license also because I had a really hard time deciding who to give the license to, partly because there were ultimately only two people in the race, Juan and Thysje. If you’d like to read their comments about their experiences trying Capture One Pro please visit the post for Episode 702 and scroll down to the comments. Both made some great points and submitted lovely photos to back up their comments. Because I found it so difficult to chose, and because there were only two people in the race, I decided to simply flip a beautiful Moroccan coin that I have to get a winner. I’m doing this as I write, so we’re going to make Thysje the side of the coin with a star on it, and Juan can be the side with King Mohammed-V on it. Here goes…

Moroccan 500 Francs Coin
Moroccan 500 Francs Coin

And the winner is Juan Ernesto!

Congratulations Juan! I’m so please to be able to award you with this Capture One Pro license, which I have just sent to you by email, and I would like to thank the Phase One team as well for making this possible. Please report back at some point about your continued success using the product, and we can maybe do an interview about your experiences at some point as well, if you’re up for that.

Photographer’s Friend Update

OK, so I’ll try to keep this relatively short, but as I have always tried to update you on what I’m up to via this blog and podcast, let me tell you about the update to our Photographer’s Friend app that I’ve been working on pretty much every waking our for the last three months. After my big update at the start of this year, I started this current update with a tiny goal to add a feature that I thought might be useful, which is a way to permanently link the Hyperlocal Distance label to the Focus Distance dial in the Depth of Field Calculator. Until now, to update the Focus Distance dial with the current Hyperlocal Distance based on the sensor format, aperture and focal length, you had to tap the Hyperlocal Distance label, and then if you changed a setting invalidating the distance, the link was automatically broken.

Now, there is a padlock on the Hyperlocal Distance readout that can be tapped or long-pressed to engage, and after that, the Focus Distance dial automatically stays in sync with the other dials while the label is tapped and engaged, even if you have Pixel Peeper mode turned on, which uses the megapixels of your sensor to give a the most accurate Depth of Field information available in any app that I’m aware of. Now, this change didn’t take me that long, and I fixed a few other minor issues as well, back in March, after I got back from my final Japan Winter Wildlife Tour for this year.

Then, I thought, you know what, if I’m going to submit an update, I might as well sneak in a few other things that I’ve been meaning to do, and that turned out to be a three-month long rabbit-hole, and I’m actually still trying to dig myself out. I am incredibly proud of what I’ve been able to do, and because most of it is already working, I’m happy to share some details with you today as well, but there are a few things that I have still to overcome, so it’s probably going to be another week or two before I can get this released.

Anyway, the new feature that has taken the most time for any single feature, is a new extension for Apple Watch to link the Neutral Density filter Calculator to the watch, so that you can time long exposure photographs from your watch, instead of having to reach for your phone each time you want to run the timer, and also you don’t even have to keep your phone out during the exposure, while using the extension on the watch. You still have to apply filters on the iPhone, but there is a link button that comes to life when the Watch Extension is installed and active, that allows you to link the two timers, Here’s a photo of the two timers in action, linked and synchronized.

Photographer's Friend with Apple Watch Extension
Photographer’s Friend with Apple Watch Extension
ND Calculator Watch Extension Settings
ND Calculator Watch Extension Settings

Also notice the fancy new Font Awesome icons, which I’m gradually working into the app, giving it a more intuitive and smarter looking interface where possible, compared to the mostly button based interface that we’ve used so far. If you don’t have an Apple Watch, half of the icons you see in the above photo will never be displayed, and even if you do have a watch, some of them hide when it’s not connected and can also be manually hidden.

You can tap that gold link to break the link and run the timers individually, and you can also simply start a counter, which counts up on the watch, then save that counter as a new custom timer. You can also swipe a settings screen in from the right on the Apple Watch, and set a custom timer directly as well, so if you just need a quick timer, we have you covered. Here’s a screenshot from the watch Settings screen.

If interest in the Watch Extension is high, I will probably eventually create a standalone ND Calculator specifically for the watch, now that I know how to program for this somewhat restricted little device. I also want to go on and create an extension for the Depth of Field calculator, but that is a little way out yet.

Smart Rotation

Also notice how the screen has split itself into two portions and intelligently placed them side-by-side in landscape orientation of the iOS app. There is also an option to switch which side the controls drop down to, so left handed users can have the controls drop down to the left hand side of the screen, rather than the right. For the ND Calculator, you can also two-finger drag the controls section and move it from the top to the bottom and back again, and the left-right handed stuff still works as expected.

This Smart Rotation is a new feature that is going to be part of a Pro version which I’m hoping to sell as an In-App Purchase. I’ve put too much work into this update to throw it out for free. The Watch Extension was always planned to be a paid extension, because I don’t want to charge people that don’t need the watch extension, for the watch extension, although I’m still working on this for both apps, and have a few more hurdles to clear before I can say for sure what the final release will look like. The technology is in place, to split the functionality based on the owned product, but there is more tweaking to do on the IAP testing process, which is my next job after releasing this post.

Mac OS X

The other major change, and again, I’m still working on the release strategy, is that I now have a Mac OS X version of Photographer’s Friend, thanks to Apple’s new Catalyst technology, allowing iOS apps to run on the Mac. There’s additional work involved, so it won’t be completely free, but as an educational tool there is definitely a place for a Mac version, and I’ve found myself using it on the Mac as I’ve worked on this, so I’m looking forward to getting this out too.

Here is a screenshot of the Depth of Field Calculator on the Mac OS. If you’ve ever used Photographer’s Friend on an iPad, especially the iPad Pro with the large screen, you’ll have noticed that the text and numbers on the labels were really small. I figured out how to make it bigger on larger screens now though, so text is now much bigger on the iPad and Mac OS.

Photographers Friend on Mac OS X
Photographers Friend on Mac OS X

And, the Smart Resize is also available on the iPad and Mac OS for Photographer’s Friend Pro owners. This is great for a teaching environment when you might be showing your screen at say a camera club talk, and you can literally resize to say just a thin strip across the bottom of the screen, and the layout just works with you. Smart Rotation is also a great feature for use in the field, when we can finally get back out there, of course.

Note too that in these screenshots I have the new Hyperlocal Distance Lock that I mentioned earlier turned on, so the Hyperlocal Distance is automatically applied to the Focus Distance dial and all of the calculated distances are updated accordingly. If you turn off that lock and tap the blue Hyperlocal Distance label, your originally selected focus distance will be restored.

Photographers Friend on Mac OS X Smart Resized
Photographers Friend on Mac OS X Smart Resized

I’m working the Smart Rotation into as many screens as I can, so as with these screenshots, even the settings screens are looking pretty fancy when in landscape orientation, compared to the squished down portrait orientation screens that are in the currently released version. These are iPhone screenshots by the way. I’m still working on this for the Mac OS version settings screens, but hopefully it will be included in the upcoming release as soon as I can iron out these last few issues that I’m working on.

Smart Rotation Settings
Smart Rotation Settings

As I say, some of this has taken so much work that it won’t all be free, although some of these changes may be integrated into an update for the currently available app for free if you already own Photographer’s Friend, and if I can figure out how to do the rest of what I want to do via In-App Purchases. All will be clear in the next few weeks hopefully. If you don’t yet own Photographer’s Friend and want to hear more when I release the update, please subscribe to my newsletter. Also sign up if you want to know when I finally get you an Android version. I promise that this will be the next thing I work on once I get this release out.


Show Notes

Try Capture One Pro yourself here: https://www.captureone.com/en

See details of Photographer’s Friend here: https://mbp.ac/app

Music by Martin Bailey


Audio

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Download this Podcast as an MP3 with Chapters.

Visit this page for help on how to view the images in MP3 files.


Photographer’s Friend Depth of Field Calculator Tutorial (Podcast 634)

Photographer’s Friend Depth of Field Calculator Tutorial (Podcast 634)

For this week’s episode, I’m releasing a new tutorial for our Photographer’s Friend Depth of Field calculator, and I’ve included some practical examples from the field so this may be useful as a general tutorial, even if you don’t own Photographer’s Friend.

I was actually going to just release this video in the background, but with a bunch of stuff that came up and the fact that it’s supposed to be a holiday in Japan today, I decided to make this it for this week. If you are completely uninterested in our iOS app and have no interest in Depth of Field, I have a nice meaty episode lined up for you next week, so please stay tuned.

If you are interested in the new tutorial though, I’ve embedded it below, and you can also find it on our Photographer’s Friend Tutorials page. Also, a quick shout out to listener Ron Paynter in Australia, with a thank you for pointing out that I had a typo in the Startup Help for the Exposure Shift calculator. I can’t believe I missed out the “f” in Shift, but thanks for bringing some laughter to our breakfast table yesterday morning Ron.

I was actually working on a minor update to the app anyway, so the typo has been fixed in version 3.0.4 which is already on the App Store ready for people to upgrade. Anyway, here is the video, which I hope you enjoy, and I’ll be back with another episode next week.

You can see more details on the Photographer’s Friend product page.


Show Notes

Find out more about our Photographer’s Friend app for iOS on the product page here: https://mbp.ac/app.

Music by Martin Bailey


Audio

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Download this Podcast in MP3 format (Audio Only).

Download this Podcast in Enhanced Podcast M4A format. This requires Apple iTunes or Quicktime to view/listen.



Photographer’s Friend 3 for iOS Now Available! (Podcast 632)

Photographer’s Friend 3 for iOS Now Available! (Podcast 632)

I’m incredibly happy and proud to tell you that our iOS app Photographer’s Friend version 3 is now available on the App Store! I was able to create an upgrade option as well, so today I’m going to fill you in on all the details.

It took me a few weeks longer than I’d hoped because I decided to add one last feature that proved to be a lot more difficult than I’d imagined, but as I knew it would be necessary, I think it was worth spending the extra time. I also really wanted to provide a way for existing Photographer’s Friend 2 owers to get a discount on the upgrade, and this took a few more steps that also delayed this announcement.

But, I am really happy to tell you that Photographer’s Friend 3 is now available in the App Store, and I was successful in setting up a mechanism to get existing customers a discount, and you don’t see that very much in the App Store. Basically what I’ve done is created a bundle, which is usually a way for companies or developers to sell additional products to customers at a discount. Our Photographer’s Friend Upgrade Bundle though does just that—provides a way to upgrade with a discount.

How it works is this. If you bought version 2 and probably also if you got version 2 as a free upgrade from version 1, you should see the words “Complete My Bundle” when you visit the bundle page. The price of the bundle is $6.99 US, but the amount that you originally paid for Photographer’s Friend is automatically deducted, resulting in a discount.

Photographer's Friend Upgrade Bundle with QR Code

Another cool coincidence is that iOS 12 has just been released and in the Control Center we now have a button to start a native QR code reader, and I love QR codes! If you start the QR code reader and point it at the code above, you will be able to automatically just to the Upgrade Bundle on the App Store to upgrade to version 3 at a discount. If you want to upgrade of course. 

If you are happy with the two calculators in version 2, you are most welcome to stick with version 2, but please note that all new features moving forward will be added to version 3. We did just release a small update to version 2 though, to make the Depth of Field calculator a little more accurate, so you aren’t being left out to dry.

There were various prices for version 1 and 2 over the years, ranging from an introductory price of $2.99 which then changed to the regular price of $3.99. If you paid $2.99 for your previous version, that is deducted from $6.99, meaning you’ll be able to upgrade for $4, a saving of 20% over the cost of version 3 which is $4.99. If you paid $3.99 for a previous version, you will be able to upgrade for $3, which is a saving of 40% off the full price.

I love this way of providing a discount because it’s completely fair in my opinion. People who paid less earlier pay more now, and people who paid more, now pay less. There’s a beautiful almost Kharma-like harmony to that!

In version 3, I’ve just posted a minor update for review by Apple with some under the hood updates, and a few more tweaks to the number of decimal places displayed in the Depth of Field calculator, making it even more useful when working with very shallow depth of field.

Introducing the Exposure Shift Calculator

The major update, of course, is the addition of a third calculator that I’ve called the Exposure Shift Calculator, rounding out the team of photography assistants in your pocket, and removing any confusion over how to change your exposure, or finding good settings from a light meter’s EV reading.

Rather than going through all of the details here though, I’ve created a video to walk you through this new calculator, which you can see below.

This video is one of three that I’ll be creating to explain each of the three calculators, and these are now linked to an Online Video Tutorial page under the Links and Help sections in the Photographer’s Friend app, so I hope you find these useful. There is still a help section for each calculator inside the app, that you can reference without an internet connection, as I know many people use the app in situations where connecting to the internet isn’t possible, due to either location or cost constraints.

Photographer's Friend on App Store

Do let me know what you think of the new calculator, and once again I’d like to thank listener Steve Jarrel who provided the initial idea for the Exposure Shift Calculator, although my implementation may not be quite what he had in mind. I know from experience of talking about exposure in the field, that these exposure shifts can be confusing to calculate, so I think this will have practical uses.

Also, I think it’s great as an educational tool. There are situations when teaching photography when I wished I had a way of graphically showing how the Aperture affects the Shutter Speed, or the ISO affects the Aperture, and I can now lock any one of the three dials in the Exposure Shift Calculator and show just that, as we move any of the two dials that are not locked. And the Exposure Value lock moves all both of the free dials as you move a third, which again, is a great educational tool, and a way to find good settings changes based on EV readouts from a light meter.

Of course, just playing with the calculator is a great way to get a better understanding of how exposure settings affect each other, so I urge anyone that buys Photographer’s Friend to play away, and build a better understanding, so that you don’t struggle with this stuff in the heat of the moment in the field.

Anyway, as I say, I won’t try to explain this all in words, as the video will be much easier to understand, so please do take a look. If you don’t yet own Photographer’s Friend, but would like to buy it, you can use the QR code here to jump to the App Store or simply type in https://mbp.ac/pf3 in your browser on your iPhone or iPad, or search for Photographer’s Friend in the App Store. Do make sure that you buy version 3 though, and not version 2, unless you really don’t need the Exposure Shift calculator and want to save a dollar. If you’d like more written information before deciding if Photographer’s Friend is for you or not, the product page is here.

Download Photographer's Friend on the App Store

Apple, the Apple logo, iPhone, and iPad are trademarks of Apple Inc., registered in the U.S. and other countries and regions. App Store is a service mark of Apple Inc.

Android Version on the Way

I also wanted to say before we finish, that I am looking into a way to port the code that I have to Android, and hope to be able to bring you an Android version before too long. I know you want it, it’s just a matter of making the time now to make it happen, but I am on it.


Show Notes

Get Photographer’s Friend 3 here: https:///mbp.ac/pf3

Check out the Upgrade Bundle here: https://mbp.ac/pfbundle

And the Photographer’s Friend product page is here: https://mbp.ac/app

Music by Martin Bailey


Audio

Subscribe in iTunes for Enhanced Podcasts delivered automatically to your computer.

Download this Podcast in MP3 format (Audio Only).

Download this Podcast in Enhanced Podcast M4A format. This requires Apple iTunes or Quicktime to view/listen.


Understanding Exposure Value (Podcast 630)

Understanding Exposure Value (Podcast 630)


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This week we’re going to take a look at Exposure Value or EV, and I’ll explain what it is, why it’s useful, and why I’ve spent almost every waking minute for the last 17 days building a new Exposure Shift Calculator for our Photographer’s Friend app, which we’ll use for some of my explanations.

When we talk about exposure, we generally use aperture, shutter speed, and ISO settings to relay the absolute values of our exposure, but then if you want to change one of the values while maintaining the same exposure, you have to change one or both of the other settings in the opposite direction. For example, if you are using an aperture of f/8, with a shutter speed of 1/250 of a second, at ISO 200, and I recommend that you change your aperture to f/11, which is one stop smaller than f/8, and therefore lets in half the light, you would need to adjust the other settings to counter that change.

You might change your shutter speed from 1/250 of a second to 1/125, which is twice as long, and therefore lets in twice as much light, so you maintain the same exposure. If though, for example, 1/125 of a second might be too slow and you don’t want to risk your subject moving during the exposure, making them blurry, you might decide to increase your ISO from 200 to 400, which makes it twice as sensitive, and brings your exposure back in line.

This can get a little bit confusing, especially if for example, you don’t want to change your aperture from f/8, because it provides just the right amount of depth of field for the photograph you are making, you then have to think about how you could make the same change with the other settings. If you are happy with your shutter speed, you could of course just change your ISO from 200 to 100, making it one stop less sensitive, and you’d have the same exposure as you would if you’d changed your aperture from f/8 to f/11.

Stops Explained

Although people sometimes refer to the changes made to exposure as steps, it’s more common to use the term “stop”. Before we go on, although this is pretty basic photography theory, let’s just recap that by aperture stops from say f/1.0 counting in full stops would go from f/1.0 through f/1.4, f/2, f/2.8, f/4, f/5.6, f/8, f/11, f/16 and higher. Depending on how you have your camera set up you might have half stops between these, but generally, most cameras and light meters use third stops, so for example, between f/5.6 and f/8 you will have f/6.3 and f/7.1, though this varies slightly sometimes with different manufacturers. It’s also worth noting that the smaller the number, the larger the aperture, so a lens set to f/5.6 lets in twice as much light as when it’s set to f/8, and f/11 lets in half as much light as f/8.

Stops in shutter speed terms are calculated by doubling or halving the time. For example, if your shutter speed is 1/250 of a second, making it one stop slower would be 1/125 of a second, and that is also one stop lighter because the light hits the sensor for twice as long. Making 1/250 of a second one stop faster takes it to 1/500 of a second, which is also one stop darker because the shutter is open half the time. This continues even when we’re doing long exposures of more than a second. One stop longer than 5 seconds is of course 10 seconds, and 20 seconds is one stop longer again.

ISO stops can be a bit confusing again, but similar to shutter speeds, you just keep doubling or halving the value for each stop. ISO 200 is one stop more sensitive or brighter than ISO 100. ISO 400 is one stop brighter than 200, and two stops brighter than 100. If we keep going, we’ll work through ISOs 800, 1600, 3200 and 6400 etc. The thing to be careful with of course is that very high ISOs can start to introduce noise or grain to your images, but I’ll regularly shoot at ISO 5000 or 6400 if necessary to get the shot. It comes down to testing your camera to see how much noise is introduced in various conditions and how comfortable you are with it.

Exposure Value Stops

So, following that recap, let’s talk about Exposure Values, which are also referred to as stops, but they can be more useful because when you refer to exposure in EV or Exposure Values, it’s not tied to any one setting. According to Wikipedia, the Exposure Value system was invented in the 1950s and uses a relatively simple formula to calculate a value that can be used to represent any combination of our camera settings.

The EV scale can also be mapped to various lighting conditions, for example, if you’ve heard of the “Sunny Sixteen” rule, which is a basic guideline to set your camera aperture to f/16 and use your ISO as the shutter speed, so at ISO 100, you’d set your shutter speed to either 1/100 or 1/125 of a second. This will get you a relatively good exposure on a sunny day, hence the name, sunny sixteen.

Well, on the EV scale, the sunny sixteen rule equates to 15 EV. On a slightly overcast day, you might open up your aperture from f/16 to f/11, one-stop wider, and this would mean you were shooting at 14 EV. For an overcast day, you might go to f/8, another stop wider, and that is EV 13. Conversely, you might increase your ISO from 100 to 200 for a slightly overcast day or from 200 to 400 for an overcast day, and of course, you could change your shutter speed, but if you have an Exposure Value to work to, it’s pretty easy to recalculate your settings.

EV zero

If we keep going back, the zero base for our scale can be represented as an aperture of f/1.0 for one second at ISO 100. This is EV o (zero). We can go darker, using negative numbers. For example, on the EV scale we have the Aurora Borealis at between -3 and -6 EV, and the Milky Way and Galactic Core at between -11 and -9 EV. I actually found these old values to be a little bit too dark if I compare them to my own images, such as for example, the settings I used for this photograph of the Galactic Core that I shot on my Namibia Tour this year.

Milky Way Galactic Core
Milky Way Galactic Core

I shot this at f/1.4 which is one EV more than f/1.0, putting me at EV 1. I was using a shutter speed of 5 seconds, so to continue with our mental arithmetic to see how this changes our Exposure Value number, first I double the exposure from one second to two, which takes the EV back to zero, then double the exposure again to four seconds, which takes us to -1 EV. Another second to 5 is one-third of a full stop, so that takes our EV to -1 ⅓.

I also changed my ISO from 100 to 3200, so let’s see how this affects the Exposure Value. First, changing from ISO 100 to 200 makes my sensor twice as sensitive, so my Exposure Value goes up by one stop to -0 ⅓. Doubling the ISO again to 400 is another stop, so we’re back into positive numbers with 0 ⅔. 400 to 800 ISO gives us 1 ⅔ EV and 800 to 1600 is 2 ⅔ EV, then finally 1600 t0 3200 is 3 ⅔ EV.

EV Increases as ISO Increases

You might have noticed there that calculating ISO changes can be a bit confusing. For me at least, it seems as though the scale is going the wrong way, but because the EV represents our cameras ability to capture an exposure based on how sensitive the film is, the Exposure Value goes up as we make the sensor more sensitive. Before I started to really look into how to calculate Exposure Value, I would certainly have guessed the opposite way, so this has taken some getting used to.

I guess it’s easier to think of EV as the target, as in the Exposure Value of the subject, not the base, which is the settings on the camera. For example, I’ve just used a Light Meter to take an incident reading of the light on this very slightly hazy summer’s day in Tokyo, and my reading was EV 14 ⅓. We can actually adjust the sunny sixteen rule to understand that I’d get a good exposure at the moment by reducing my exposure by two-thirds of a stop from 1/125 of a second to 1/80 of a second at f/16. We’ll come back to some more examples that will make this clearer, but for now, let’s talk a little more about why using the absolute values of aperture and shutter speed etc. isn’t ideal.

Exposure Shifts

When we’re shooting on my Japan Winter Wildlife tours, we are generally using Manual Exposure, to ensure that our subjects stay well exposed whether they are over a white snowy background or a darker background like trees or the sky. This works great when the light is constant, but if there are patchy clouds, we have to change our settings quite regularly, so I shout out that I’m changing my settings to the group.

Ruffled Feathers
Ruffled Feathers

If I simply shout out that I’m increasing my exposure by one stop, which is the same as saying I’m increasing my exposure by one EV, someone will invariably ask for actual settings in aperture, shutter speed, and ISO form. Then, if for example, I say f/11 for 1/1000 of a second at ISO 800, I often get asked, what would that be if I’m at ISO 400, or what if I’m at f/8, and it’s understandable because this can be a bit confusing.

Exposure Shift Calculator

To help with this kind of exposure shift, I received an idea from listener Steve Jarrel last year, for me to add a third calculator to our Photographer’s Friend app for iOS. The implementation I’ve come up with is slightly different, but the idea is basically the same, so I’ve just this morning finished some very complicated development to create a third calculator called the Exposure Shift Calculator. This has taken so much extra work, and is such a big change that I’m actually going to make this a paid upgrade to a new version of our app, but I’m currently looking into a way to provide a pseudo upgrade price for current version 2 owners, and more details of that will follow over the next week or so.

Today though, I wanted to introduce you to the new calculator to help shed a little more light on this discussion about Exposure Values. Because Exposure Values are at the core of all exposure calculations, it is at the core of my new Exposure Shift Calculator. Here’s a screenshot from an iPad Air, showing the calculator set at zero EV, which as I mentioned is the value you get with an aperture of f/1.0 for one second with ISO 100 (below).

Exposure Shift Calculator EV0
Exposure Shift Calculator EV0

When you first start using the calculator, you can of course dial in any combination of camera settings, but we’ll work from EV zero, for now, to show you how this works. If you want to store your original settings for later reference, just tap the large Store Current Settings button in the middle of the screen, and your settings will be displayed there until you tap the settings again, which clears them and brings back the Store Current Settings button.

I might, for example, use the calculator to find some settings to give me a good exposure at 14 ⅓ EV on this sunny day in Tokyo, and as we can see if I select an aperture of f/5.6, and leave my ISO at 100, I would need to set my shutter speed to 1/640 of a second. In this next screenshot (below) I’ve stored my EV zero settings for reference, and dialed in my new settings so that you can see how the store function works.

There are two ways to experiment with your settings after this though, starting with locking a single dial. If you tap the Aperture, Shutter or ISO dial labels, that label turns into my teal blue color and the padlock shows that it is locked, and now when you turn one of the unlocked dials, the other unlocked dial will automatically update to a value that maintains the same exposure. I’ve locked the original settings in the middle of the screen for reference, and then locked the ISO dial, which would be useful say if you were shooting with film and literally could not change the ISO until the end of the roll, or for example if your ISO was already very high and you don’t want it to go any higher.

Exposure Shift Calculator at EV 14 2/3 ISO100
Exposure Shift Calculator at EV 14 2/3 ISO100

I decided that I wanted to change my aperture to f/14, my go-to aperture for most of my landscape work, and you can see that the calculator automatically calculated that I would need to change my shutter speed to 1/100 of a second to maintain my Exposure Value of 14 ⅓. I can of course then tap the aperture dial to lock that at f/14, and if I change the shutter speed dial, it will give me a new ISO to use, to maintain the same exposure. Note though, that when you lock an individual dial that enables the ISO value to be recalculated, the EV will change, because increasing the sensitivity of the ISO increases your EV, so the other unlocked dial has to move in the opposite direction to maintain the exposure.

The Challenge

That concept led me to what turned out to be the most difficult feature to code, the Exposure Value Lock. If you tap on the Exposure Value number or the padlock to its right, any individually locked dials will be unlocked, but now when you spin any dial, the other two dials will automatically update to maintain the same Exposure Value. This was particularly difficult because not only did I have to calculate two other dials simultaneously, the ISO dial has to turn in reverse to maintain the Exposure Value. 

Exposure Shift Calculator Aperture Locked
Exposure Shift Calculator Aperture Locked

For example, if I lock the aperture dial at f/14 and change the shutter speed from 1/100 of second to a 1/200 of a second, the ISO would change from 100 to 200, to counter the shutter speed change to maintain the same exposure, but because increasing the shutter speed increases the EV by one stop and making the ISO more sensitive also increases the Exposure Value, my EV changes from 14 ⅓ to 16 ⅓.

Exposure Value Lock

So, to lock the EV, I actually have to rotate the ISO dial in the opposite direction to ensure that the Exposure Value is maintained, rather than the Exposure. I know that sounds weird, but that’s what this took to achieve and actually provide a useful EV Lock feature. If for example I have a meter reading of 16 ⅓  wanted to  EV, and I wanted to open up my aperture to f/2.8 for some nice shallow depth of field, by locking the EV and selecting f/2.8 on the aperture dial, the calculator gives me a shutter speed of 1/1000 of a second at ISO of 1000.

Calculated Exposure Value Locked Shift
Calculated Exposure Value Locked Shift

That’s useful to see your options while maintaining the EV, but in this case, if you know that you want an aperture of f/2.8 and because you know that you have plenty of light, rather than locking the EV and going fully automatic, it would be better to simply lock the ISO and move your aperture dial to f/2.8 and then you’ll get your new shutter speed of 1/5000 of a second, for a great outdoor exposure on a theoretically very bright sunny day.

ISO Locked Exposure Shift to f/2.8
ISO Locked Exposure Shift to f/2.8

Send To Buttons

If, for example, you don’t want the water in the fountain behind your model to be completely frozen by a shutter speed of 1/5000 of a second, you might decide to apply some neutral density filters, and to save you the trouble of remembering your shutter speed, I’ve also added a To ND Calc button at the top of the screen, above your calculated shutter speed, which, as you might imagine, will send your new shutter speed directly to the ND calculator and open it for you. This is also useful if you have calculated a shutter speed of five seconds or more and need a timer. Just jump over to the ND Calculator and hit the timer button.

Likewise, the To DoF Calc button will send your aperture to the Depth of Field calculator so that you can see how much depth of field you have at the currently selected or calculated aperture.

So, I hope this has helped a little if the concept of Exposure Values wasn’t something that you are familiar with. As with the other two calculators, as well as actually helping you to work in the field, they are great for learning the theory behind exposure and depth of field, as well as teaching it. Even if you have all this down, there’s nothing like being able to turn dials and show the effects of your changes to help people understand this stuff. Then hopefully when you are advised to increase your exposure by one or two stops, you’ll be better equipped to calculate the difference in your head, or reach for your iPhone and open the Photographer’s Friend.

Photographer’s Friend 3 Coming Soon!

As I said, my current plan is to make this a paid upgrade, so if you like what you see, but don’t already own version two, then please wait for a few days until I release version three. If you are reading or listening after more than a few days into September 2018 though, version three should already be available. And for those of you that have version two, I will try to provide a reasonable upgrade path, details of which will be provided in an update to version two of the app. If you don’t need the Exposure Shift calculator, you are more than welcome to continue to use version two, and I have a few improvements for version two that will be released very soon as well, so you won’t be left out to dry.

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Show Notes

You can get Photographer’s Friend in the Apple App Store here: https://mbp.ac/pf

I’ll update this post with a link to version three soon! If I forget, see the ad below. 🙂

Music by Martin Bailey


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