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by Phocal 4 months ago in camera · updated 3 months ago

Depth of Field Misconceptions when using Telephoto Lenses

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 800, 1/640 @ ƒ4.0, Focus Distance 19.32’, DoF 1.75”

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.

Olympus OMD EM1 w/ Olympus ZD 150mm ƒ2.0 - ISO 200, 1/2000 @ ƒ4.0, Focus Distance 23.49’, DoF 10.5”

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).

Olympus OMD EM1 w/ Olympus ZD 150mm ƒ2.0 - ISO 200, 1/1250 @ ƒ2.0, Focus Distance 5.25’, DoF 0.25”

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.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 1000, 1/640 @ ƒ4.0, Focus Distance 21.39’, DoF 2.1”

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.

We will start off with an example of extreme distance that I see pretty regularly, airshow photography. It is not unusual for me to see airshow photography where the photographer has stopped-down to ƒ8 or more. When I ask them why they stopped-down the answer is always to increase the DoF to get the entire plane in focus. This answer always makes me chuckle as well as wonder why photographers don’t put a little more research into what they are doing. Which by the way is what prompted me to write this article. In the below photograph I was using my Olympus MZ 300mm ƒ4.0 IS Pro as well as the Olympus MC-14 (1.4x teleconverter) for a focal length of 420mm. Using an aperture of ƒ5.6 (wide-open) with a focus distance of 1075 feet I get a huge DoF of 336 feet (168/252). The wingspan of an F-16 is 33 feet (length 50), so plenty DoF with no need to stop-down, yet I see it all the time.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 + MC-14 - ISO 200, 1/5000 @ ƒ5.6, Focus Distance 1075’, DoF 336’ Click here to purchase this photograph

Sorry about using the airshow photograph in an article about wildlife photography but I wanted to show that the DoF can be very large. With that out of the way we can get into the meat of the subject.

I was fortunate to have a Red Fox (Vulpes Vulpes) start from 100 yards down a trail and get to within a few feet of me a couple of years ago. This provided me the opportunity to photograph the same subject from what I call typical distances for most people down to my usual up close and personal distances. This series of photographs is also what gave me the inspiration to finally sit down and write this article.

All of the photographs I will be posting have no crop to them and were taken with an effective 600mm lens. I mention this because it helps to know the focal length and how large the fox is in the viewfinder when determining distance.

When I saw her pop out on the trail I slide down the small bank along the trail and laid down. I prefer to shoot my subjects from their eye level, it puts you into their world when viewing the resulting photographs. I estimated the distance to be around 100 yards and knew that shooting wide-open would give me more than enough DoF. The two images below were taken from a distance of 287 feet (so my estimation was pretty spot on) with a DoF of 33 feet (17/25). This distance is probably typical to a bit on the long side for most photographers, especially when it comes to bird photography. Despite having more than enough DoF at this distance I will still see people stopping-down to gain DoF.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 800, 1/800 @ ƒ4.0, Focus Distance 287’, DoF 33’
Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 500, 1/800 @ ƒ4.0, Focus Distance 287’, DoF 33’

When I laid on the ground it really peaked her interest, something I have learned works with a lot of wildlife. She headed straight for me with a few pauses along the way which provided a chance to capture a number of photographs as she approached. I don’t like photographing wildlife from a long distance like in the photographs above, prefer my subjects being a lot closer. So I didn’t shoot anymore images until she got closer, 150 feet to be exact, which gives me a DoF of 9 feet.

Initially that seems like more than enough DoF, but is it? We will dig into this photograph to get a better understanding on how DoF works. I said the photograph has 9 feet DoF and I have estimated her to be about 5 feet long from tip of nose to tip of tail. But we have to keep in mind that DoF is divided in half with half in front of and half behind the point of focus. Her tail is not straight out, so I would put her total length to be around 4 1/2 feet. With my focus point on her eyes (which is where you should always put the focus point) I have just enough DoF to get her entire body. What if I was shooting a full frame camera? 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? Do we need her to be in focus from nose to tail? That is a question we will discuss in a bit more detail later.

A full frame camera and 600mm ƒ4.0 lens is an expensive setup, which puts it out of reach of most hobbyist photographers. The most common wildlife setup is an APS-C camera combined with one of the 150-600 ƒ5.0-6.3 lenses. 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.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 500, 1/800 @ ƒ4.0, Focus Distance 150’, DoF 9’

I know for this article I am using photographs of a fox but the most common wildlife subject is probably birds. I often see photographs of larger birds like Herons and Egrets taken from the same distance as the photograph above where the photographer has stopped-down. When I comment about it they will always say to get more DoF so they have the entire bird in focus. As you can see in the photograph above there is no reason to stop-down for a bird when I can get a fox fully in focus shooting wide-open.

When she got 95 feet away I captured the below photograph with a DoF of 3.6 feet (1.8/2.7). This is the first photograph where I didn’t get her entire body in focus. Even if I had enough light to stop-down and keep my ISO low I would have still shot wide-open. I personally don’t think the entire subject has to be in focus to make a compelling image, but if I was shooting full frame we are getting into the realm of when I would consider stopping-down. This image shot with the most common APS-C setup would have provided a DoF of 4.3 feet, once again more than what I had with my gear and plenty for the photograph.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 500, 1/800 @ ƒ4.0, Focus Distance 95’, DoF 3.6’

This next photograph was taken later in the day but from the same distance as the photograph above. The big difference is that she is perfectly broadside to me, which makes needing more DoF moot. When you are shooting with limited DoF the positioning of your subject can be crucial in creating a compelling image. One way to do that is shoot profile images where you can capture a lot of detail without needing much DoF, like I did here. This is also what I consider a good environmental portrait. I haven’t completely blown out the background, which gives you an idea of the environment in which she lives. One other thing of note is that since she was standing still I dropped the shutter speed down so I could also lower my ISO, increasing my image quality significantly.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 250, 1/320 @ ƒ4.0, Focus Distance 95’, DoF 3.6’ Click here to purchase this photograph

It only took her 20ish seconds to go from 95 feet to 62 feet away. When she got there she became a little hesitant: stopped, walked around a bit, stopped, walked around a bit………..Like she was trying to ascertain what exactly this human laying in the snow was doing. While she was trying to make up her mind I captured a couple of photographs with a DoF of 1 1/2 feet (0.76/1.15). In the first photograph she is at about a 45 degree angle and in the second she is almost completely broadside. Using my gear or an APS-C camera I wouldn’t stop-down in this situation because I feel both setups provide enough DoF. With a full frame camera we are now at the point where I would seriously consider stopping-down to get a bit for more DoF. In this situation with a full frame camera you will have enough DoF to also get her nose, ears and chest (in the 45 degree angle photo) and I feel this is enough. But this really comes down to personal preference and shooting style, I would shoot it wide-open.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 400, 1/640 @ ƒ4.0, Focus Distance 62’, DoF 1.5’
Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 500, 1/640 @ ƒ4.0, Focus Distance 62’, DoF 1.5’

After a minute or so she decided I wasn’t threatening and headed towards me once again. As she was walking towards me I captured this image at 59 feet with a DoF of 1.4 feet (0.68/1.0). Using my gear or even APS-C I wouldn’t stop-down yet. There is enough DoF to get nose to ears (which includes the chest) in focus, I don’t feel you need more than that to make a compelling image. Now if shooting full frame, we are in the realm of stopping-down to increase DoF. With a full frame camera her eyes would be about all that is in focus. There is just not enough to get her nose, ears, and chest into focus and therefore doesn’t really create a compelling image. I would stop-down a full frame camera to ƒ8.0 and be right were I am at with my camera and lens.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 500, 1/640 @ ƒ4.0, Focus Distance 59’, DoF 1.4’

What if in the photo above I did want all of her in focus? What would I have gained? What would I have lost? When stopping-down to get more DoF you have to change either shutter speed or ISO to keep the photograph properly exposed. Since she was moving around (sometimes pretty quickly) I would not feel comfortable lowering shutter speed and potentially getting blurring photos from motion, was already in danger of that at 1/640. So the only option would be to raise ISO, but there are problems with doing that. Higher ISO’s introduce noise into the photograph as well as rob it of detail. The higher you go the more noise and less detail is captured. To get all of her in focus I would have had to stop-down to ƒ22 which would have raised my ISO to 16,000, well above my comfortable limit of 3200. In the current photograph she is well separated from the background, which makes her pop. Stopping down to ƒ22 would create a much busier background (similar to the one in the first photos of her at 100 yards) and cause her to not be so prominent and the image would lose its appeal.

After her hesitation at 62 feet she decided I wasn’t a threat and moved without stopping into the 10 to 20 foot range. Once in that range she spent three to four minutes running/jumping and dropping down to the ground, reminiscent of a puppy trying to get you to play. Not sure how long she would have hung around doing that because a cross-country skier came by, so she ran off into the woods until they passed. While she was having fun trying to get me to react I was able to capture a few images from a distance of 16 to 21 feet.

The next two images were captured from a distance of 21 feet with a DoF of 2 inches (1/1.5). We are now getting into the razor thin DoF that people believe you always have with telephoto lenses. This is also getting into the distances that most normally don’t shoot from because they are unable to get that close to wildlife, a skill that takes years too perfect.

In the first image she is completely broadside and even with only 2 inches DoF the image works since all the important parts are in focus. Shooting full frame I would have stopped-down to around ƒ8.0 because 1 inch is just not enough. In the second image she has turned her head and is looking right at us. Her nose and ears are not within the DoF but my lens has a nice smooth fall off (the characteristics of lens as it goes from in focus to pure blur) and keeps enough detail in them to still make the image compelling.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 1000, 1/640 @ ƒ4.0, Focus Distance 21’, DoF 2.0”
Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 1000, 1/640 @ ƒ4.0, Focus Distance 21’, DoF 2.0”

My favorite photo of the day was taken from 19 feet away with a DoF of 1.7 inches (0.85/1.28). She did this a number of times, sometimes getting lower, in an attempt to get me to react. It was so much fun watching her interact with me and wish I the skier hadn’t come by when she did. Unlike the photograph above, we only have her eyes in focus. The ears are blurred out, her nose is buried in the snow, and there is an intense look in her eyes. Even with only the eyes in focus that intense look sells the image by drawing you in and making you wonder what is she thinking. Shooting full frame I would have already been stopped-down to ƒ8.0 but this image would probably work if shot at ƒ4.0.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 800, 1/640 @ ƒ4.0, Focus Distance 19’, DoF 1.7” Click here to purchase this photograph

We are now into the razor thin DoF realm but compelling images are still possible. This image was taken from 18 feet and has a DoF of 1.4 inches (0.7/1.1) but since she was completely broadside everything is in the DoF. I would have stopped-down a full frame camera to ƒ8.0, the DoF would have just been to thin for my taste.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 1000, 1/640 @ ƒ4.0, Focus Distance 18’, DoF 1.4”

The final image was taken from 16 feet and only has 1.2 inches DoF (0.6/0.9). This photograph is right on the verge of not having enough DoF. The nose holds enough detail but the fur in the ears is getting to be a little too blurry. At an aperture of ƒ8.0 the fur in the ears would be clearer and the image would be more compelling. If I was shooting a static subject I would have stopped down while also lowering the shutter speed to keep ISO reasonable. While I did mention my high ISO limit was 3200, I really prefer to say below 2000. I only go above 2000 for exceptional images, even though the results are not always to my satisfaction. Given I was shooting action in terrible light conditions ƒ4.0 was the best option.

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 800, 1/640 @ ƒ4.0, Focus Distance 16’, DoF 1.2”

This article has been in my head for a few years now and I hope you have found it helpful. I had originally planned on digging through my thousands of bird images and using them but after my encounter with Gorgeous (as I have named her) I opted for her. I chose using her because if I can get all of her in focus without stopping-down there is no reason to stop-down on a bird. I also feel like using the same subject throughout the distances really helps with understanding how DoF works with telephoto lenses.

My general rule of thumb for people is until you are filling 3/4 of the frame with your subject there is no reason to stop-down. This works regardless of the subject size because for larger subjects you will be further away so DoF will be greater. Even when filling the frame with your subject you typically will not have to stop-down to make a compelling image, this is more a shooting style preference. It is when you start getting close enough for head/shoulder portraits that you need to start paying attention. You can keep shooting wide-open but use subject positioning to increase what is in focus, like shooting profile images. Or you can stop-down to increase your DoF, just make sure your shutter speed doesn’t drop to low or your ISO goes higher than you are comfortable with.

I have uploaded full resolution images from the article to this Flickr album so you can view them in greater detail.

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If you would like to view more of my photographic work or purchase some of the images in this article visit my website https://phocalart.com

Phocal

Olympus OMD EM1 w/ Olympus MZ 300mm ƒ4.0 - ISO 200, 1/320 @ ƒ4.0, Focus Distance 61’, DoF 1.5’

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Phocal

I am outdoor adventurer and wildlife photographer who also enjoys story telling.

See as well as purchase my photographic work here: https://phocalart.com

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