Wildlife Photography: Understanding the DoF Misconception of Telephoto Lenses

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So this has been in my head for a few years now but for some reason every time I sat down to write it up I would get nowhere. Well I finally got around to finishing it up and I am also trying something new with this post.

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Gorgeous by Phocal Art, on Flickr

I am a wildlife photographer who likes to get close to my subjects since that is where the details are. The downside to getting close is dealing with a narrow Depth of Field (DoF), like the photograph above, when I can’t stop-down because the light is low and it will raise my ISO beyond what I’m comfortable with. There are also times when close with good light that I can stop-down to capture all that amazing detail like the image below.

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Sexy by Phocal Art, on Flickr

While laying at the edge of a swamp photographing baby gators with a DoF of 1/4 inch I don’t have time to shoot multiple images at various apertures when mama gator is lurking not far off. Yes, DoF is something I consider when shooting, along with composition, perspective, and shutter speed (freeze or show motion).

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Unsure by Phocal Art, on Flickr

Part of my image processing includes getting the focus distance from the EXIF and figuring out the DoF for the image. I do this to keep my skills sharp for when encountering a new subject like the fox in the photograph below. It was cloudy and snowing, which was going to force me to shoot at higher ISO’s. She was close and while great for filling the frame would also create some narrow DoF. Since she was moving around I wanted a somewhat higher shutter speed and to keep the ISO as low as possible I elected to shoot wide-open at ƒ4.0. I knew this was going to create shallow DoF, but I also knew that it would be enough for a compelling image.

49179128182_06297616d5_o.jpg
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Gorgeous 016 by Phocal Art, on Flickr

Wait a minute! You said this article was regarding the misconception about DoF and telephoto lenses yet three out of your four examples show a narrow DoF?

Well, There is a misconception about DoF and telephoto lenses. People seem to believe when shooting a telephoto lens you will always have a narrow DoF like in my above images. This is not true.

Before getting into the nuts and bolts there are three things that need to be clarified.

To begin with, Depth of Field (DoF) is the area in an image that appears to be in acceptable focus. It is determined by the focus distance, lens focal length, and aperture. If I change any one of those the DoF will change in a predictable manner. If focus distance is increased the DoF will increase as well. As aperture decreases (the number gets bigger) the DoF increases. Finally, when focal length increases DoF decreases. That last part is what helps create the misconception about telephoto lenses having this razor thin DoF. Is it smaller than a normal focal length lens? Yes, it is, but not nearly as extreme as people tend to think.

The second is how terrible most people are at judging distance. When looking at photographs people post I find that most tend to really underestimate their shooting distance. When asked how far away they will say x number of feet but when I download the image and look at the EXIF it turns out they were twice that distance or more. To really use DoF to your advantage as a wildlife photographer you need to be good at accurately judging distance, it is the only parameter you have little to no control over. When in the field I am always estimating distance and then walking it off to keep my skills sharp.

The final item is a short discussion about cameras and sensor size. This topic can go down a serious rabbit hole, so I will keep it short and simple. I shoot Olympus which uses the µ4/3’s sensor with a 2x crop factor. This means that the effective focal length of my lenses is 2x, so my 300mm lens gives the same field of view as a 600mm on a full frame camera. It also gives me 2x the DoF than a full frame camera, which has advantages and disadvantages. A full frame camera has a sensor the same size as 35mm film and is the reference standard for other sized sensors. I should note here that when using a full frame camera the focal length on the lens is the field of view the lens will provide, unlike other sized sensors where you have a crop factor as in my 2x. The other typical sensor size is APS-C which has a 1.5x (Nikon, Sony) or 1.6x (Canon) crop factor depending on manufacturer. Throughout this article I will refer to the DoF based off of my camera and in parentheses list full frame and APS-C respectively. To keep things simple I will only be using 1.5x for APS-C.

You can finish reading the article here. This is my first time using Vocal, going to throw up a few articles and see how it goes. I am already not impressed because they put it in Pet Life despite me selecting photography when I submitted it, waiting for a reply to my email. When the link changes I will update the link here.

Phocal
 
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Hypilein

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Really informative article. The key points were already something I suspected, but you laid out your arguments really well and the imagery made for a pleasing read. I have to say though that the image quality at the platform is much worse than the images you posted here, but that is probably not under your control.
 

Bushboy

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What are your thoughts on the, in camera focus stacking, with these wide aperture telephotos?
 
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Really informative article. The key points were already something I suspected, but you laid out your arguments really well and the imagery made for a pleasing read. I have to say though that the image quality at the platform is much worse than the images you posted here, but that is probably not under your control.

Glad you found it informative. The problem is it is really a writing platform and not a photography platform. They have been updating and adding things, so I am hoping they up the photo quality. I did end up creating a Flickr album with all the images from the article and put a link to it at the end, best I can do for now.
 
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What are your thoughts on the, in camera focus stacking, with these wide aperture telephotos?

Problem is focus stacking only works if the subject is not moving. For things like gators or snakes or other things sitting perfectly still it would work, but any movement is going to cause problems with the stack.
 

gwydionjhr

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Great article. I'm curious, why no mention of hyper-focal distance?
 

doady

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Coming from a small-sensor point-and-shoot camera, the DOF thing is still kinda new to me, so I have just used F4 at 100mm for wildlife so far just to practice with shallow DOF and also practice placing the focus point, and there are only a few situations where I wish I used F5.6 instead. I also usually use ISO 200/250 just to test the limit of my handholding ability.

The idea of getting camera down the eye level of the animal is very interesting, extra effort and thought into photography, and it really shows in the quality of the photographs.

I kinda wish you also used metres as distance, not just feet. Feet and inches is normal for height for me, but for distance it is not as intuitive, harder to imagine or envision distance in feet. Just a small thing, still a great article and great pictures.
 

gwydionjhr

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I kinda wish you also used metres as distance, not just feet. Feet and inches is normal for height for me, but for distance it is not as intuitive, harder to imagine or envision distance in feet. Just a small thing, still a great article and great pictures.

I knew you were Canadian the minute I read this.
 

pdk42

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Interesting article Ronnie. I guess I’ve been doing photography for too long (coming up 50 years now!), so there was little there that was a surprise to me.

In practical terms though, I’m asking myself what the average wildlife photographer can do. Generally speaking, most people shooting wildlife with long lenses will likely have little control over distance (except trying to get closer since that seems to a universal way to improve such shots); and unless the light is really strong, will likely be shooting wide open or close to it simply because long lenses with apertures wider than f4 don’t exist. So they’ll get the DOF they get and will need to deal with it. Animal pose etc may help, but of course it’ll be about catching the animal at the right time.
 

exakta

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I'm going to ask two really dumb questions.

A while ago I posted some shots wher I had used a small aperture and it was pointed out to me that the subject was so far away I could have shot wide open and had adequate DOF. So I went off to do some experiments, opened up the shots in Olympus Workspace and...no focus distance shown in the EXIF!!!

Just out of curiosity, I opened up the JPEG in Apple Photos on my Mac and the EXIF did show the focus distance, but was missing many other fields that Workspace displayed.

Even more annoying is that I don't see any way to get my E-M10 display focus distance, while my Fuji X10 not only showed the distance it also had DOF markings, like a manual focus lens.

1. What application for my Mac do I need to display 100% of the data stored in the EXIF?

2. What m43 cameras (if any) can display the focus distance wile shooting (not counting using lenses with focus scales)?
 

archaeopteryx

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This means that the effective focal length of my lenses is 2x, so my 300mm lens gives the same field of view as a 600mm on a full frame camera. It also gives me 2x the DoF than a full frame camera, which has advantages and disadvantages.
This claim appears to be based on
  1. A constant subject distance, implying the effect of horizontal and vertical angle of view differences between 3:2 and 4:3 on composition was neglected.
  2. A 135 aperture two stops slower than μ43.
  3. A circle of confusion invariant of sensor pixel pitch.
These assumptions aren't supported in the article, none of them seem especially realistic, and I can't really replicate the 2x depth of field claim since more plausible values give 1–2x depending on the tradeoffs made. Probably most influentially, the constant circle of confusion performs comparison between 20 MP μ43 and a 135 body with an 80 MP sensor, something which isn't functionally relevant as no 80 MP 135 bodies exist.

So it seems appropriate check the maths used and, quite possibly, revise the article for clarity and specificity and to reduce bias. It looks like the calculations were done with a circle of confusion around 14.7 or 14.8 μm which doesn't seem clearly motivated as it's 1.56 Bayer cell diagonals on a 20 MP μ43 sensor. It also appears most of the 135 DoF statements are incorrect and some of the APS-C statements are difficult to follow. Three operating range bands on a graph would communicate more DoF information than the current text more succinctly and with less opportunity for error.

That would have given a DoF of 4 1/2 feet (APS-C would be just under 7 feet), so a little over 2 feet either side of the focus point. Stopping-down to ƒ8.0 would give the same DoF as my Olympus gear in this situation, but is it really necessary?
This is inconsistent with the 2x claim made. Perhaps you meant stopping down to f/16.

Using this setup for the below photograph would provide a DoF of almost 11 feet. You end up with more DoF with this setup because the largest aperture the lens has at 400mm (which would give the same FoV) is just under ƒ6.3.
f/6.3 is the aperture at 600, not 400. It appears 400 f/8.7, presumably with a circle of confusion again near 14.8 μm, was used in the DoF calculation. Given these inconsistencies the reasoning of this particular paragraph does not appear meaningful.

This image shot with the most common APS-C setup would have provided a DoF of 4.3 feet
Assuming the APS-C circle of confusion remains 14.8 μm, a 4.3 foot DoF implies a 450 mm f/11. It's unclear this is a relevant comparison.

I would stop-down a full frame camera to ƒ8.0 and be right were I am at with my camera and lens.
I can't replicate this claim. 600 f/8 14.8 μm CoC at 18 m is 21 cm DoF, not 42 cm. This appears to be the same f/16 mistake as made above (more specifically, f/16.3 in this case).

Shooting full frame I would have stopped-down to around ƒ8.0 because 1 inch is just not enough.
But 600 mm f/8 14.8 μm CoC at 6.4 m is a 1 inch DoF. Presumably the f/16 error again.

My favorite photo of the day was taken from 19 feet away with a DoF of 1.7 inches (0.85/1.28).
I get 42 mm, which is 1.6 inches, so there appears to be a 0.1 inch discrepancy here. For the next image I get 37 mm rather than the 1.4 inches claimed, suggesting a second 0.1 inch discrepancy in the opposite direction. Since the μ43 DoFs prior to this all appear to be consistently calculated. there may be some problems with formula accuracy or rounding direction. It's a bit tricky to check without the formula or specific circle of confusion. I'm using the "exact" formula for the thin lens approximation.
 
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Great write up Ronnie! I think I'll adopt the tip to walk off distances as practice, never thought to do that on a walk or hike to hone that distance judgement. Your field-craft is impeccable.

Thanks. It is 2nd nature for me to walk off distances, habit developed from teaching map & compass navigation classes.
 
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Coming from a small-sensor point-and-shoot camera, the DOF thing is still kinda new to me, so I have just used F4 at 100mm for wildlife so far just to practice with shallow DOF and also practice placing the focus point, and there are only a few situations where I wish I used F5.6 instead. I also usually use ISO 200/250 just to test the limit of my handholding ability.

The idea of getting camera down the eye level of the animal is very interesting, extra effort and thought into photography, and it really shows in the quality of the photographs.

I kinda wish you also used metres as distance, not just feet. Feet and inches is normal for height for me, but for distance it is not as intuitive, harder to imagine or envision distance in feet. Just a small thing, still a great article and great pictures.

Thanks. I always shoot my subjects from their eye level, creates a much better image in my opinion. It is probably why I rarely shoot birds up in trees, just not a fan of the perspective. Sorry about using feet but like you with feet, meters is not intuitive and I have no concept of how far 100 meters. They funny part is the EXIF has the distance in meters and I have to convert it to feet, which is easy because Siri is so helpful with that.
 
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Interesting article Ronnie. I guess I’ve been doing photography for too long (coming up 50 years now!), so there was little there that was a surprise to me.

In practical terms though, I’m asking myself what the average wildlife photographer can do. Generally speaking, most people shooting wildlife with long lenses will likely have little control over distance (except trying to get closer since that seems to a universal way to improve such shots); and unless the light is really strong, will likely be shooting wide open or close to it simply because long lenses with apertures wider than f4 don’t exist. So they’ll get the DOF they get and will need to deal with it. Animal pose etc may help, but of course it’ll be about catching the animal at the right time.

You are correct but I think you may have missed the reason why I wrote the article or I wasn't clear enough in my writing. I regularly see photos posted in forums like this one where someone has stopped down, sometimes significantly. I understand that most lenses are sharpest stopped down (with µ4/3 it is typically one stop) and it is why I always ask whenever I see a photograph where they stopped down. Maybe 1 out of 10 times (probably more like 1 in 50) they will say because it is the sharpest point of their lens. The rest of the time the answer is "to get more DoF so I can get the entire bird in focus". When I get that answers I always point out that wide-open would have had enough DoF and that by stopping down they have increased ISO which has directly effected the IQ of their photograph. Those are the people the article was directed at, the ones that will stop down because they believe they need to when they do not.
 

DeeJayK

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Great article, Ronnie! And amazing photos, too. Thanks for writing and sharing it.

I'll readily admit I have only a cursory grasp of the mechanics of imaging, but isn't it true that you can effectively omit focal length from the DoF discussion? That is, if your subject fills the frame in the same way, with a given aperture the DoF will be same for any focal length (with camera-to-subject distance obviously changing to achieve the same framing with the different focal lengths).

So, really, it's the way you're filling the frame with your subjects (which makes for the best wildlife photos) that leads to the tiny DoF. The sensor size is only relevant in that it determines what focal length you need to use to achieve a given framing.

Someone please correct me if any of these assertions is wrong.

- K
 
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I'm going to ask two really dumb questions.

A while ago I posted some shots wher I had used a small aperture and it was pointed out to me that the subject was so far away I could have shot wide open and had adequate DOF. So I went off to do some experiments, opened up the shots in Olympus Workspace and...no focus distance shown in the EXIF!!!

Just out of curiosity, I opened up the JPEG in Apple Photos on my Mac and the EXIF did show the focus distance, but was missing many other fields that Workspace displayed.

Even more annoying is that I don't see any way to get my E-M10 display focus distance, while my Fuji X10 not only showed the distance it also had DOF markings, like a manual focus lens.

1. What application for my Mac do I need to display 100% of the data stored in the EXIF?

2. What m43 cameras (if any) can display the focus distance wile shooting (not counting using lenses with focus scales)?

To start off with I have a couple of questions out of curiosity. On those shots what did you find out? Was there plenty DoF if shot wide-open? Was the person me?

Ok, there are no dumb questions. I know it is cliche but I honestly believe that.

I have been a Mac user for a really long time. I did switch to a windows PC for a few years (switched back beginning of this year) and really loved having access to EXIF Tool. Unfortunately it is a Windows only program. Now that I am back to Mac the only program I know of for pulling EXIF data out is Photoshop. If you are looking for a visual representation of what focus point was used (as in shows you on the photograph) the only programs I know of that will do that are Apple Aperture and a plugin for Lightroom that will only work on a Windows machine. Have never used Apple Photos but from your post I assume it does that as well. There are other image editing programs out there that may show that but I have never used any of them and don't know the answer to it.

There are no µ4/3 cameras that will show focus distance while shooting that I know of. I really wish they would add that feature, no reason they can't. All the information is available and it is computer screen we look at that can display any information it is programmed to.

Hopefully someone comes along with more information about programs for that information on Mac because I am curious as well. If you have any other questions ask away.
 

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