Wildlife photography is inextricably linked with long telephoto lenses. Most wildlife photographers dream of having a fast, professional lens in their arsenal. Is it just a desire to own something beautiful and expensive? Not at all. There’s a rational reason to own an exotic lens: the fast maximum aperture.
It’s usually possible to find long telephoto lenses for good prices these days. Consider lenses like the Nikon Z 180-600mm f/5.6-6.3, the Tamron 150-500mm f/5-6.7, or even the Canon 600mm and 800mm f/11 lenses. These lenses give you lots of reach as a wildlife photographer without breaking the bank. And concerns about sharpness are largely a thing of the past.
The remaining concern is one of aperture. A faster maximum aperture lets you focus more easily in low light, shoot at a lower ISO, and employ a shallower depth of field. But the difference between, say, f/4 and f/6.3 does not seem that big. Certainly not as big as the difference in price.
That gave me the idea for this article. How much of an effect does your aperture have on depth of field in wildlife photography? Is the difference between f/4 and f/6.3 enough to justify a much heavier and expensive lens? And what about lenses with a maximum aperture of f/11 – are they even worth considering? On my recent trip to Ecuador, I met several patient birds who were kind enough to cooperate with me in answering these questions.
Different Aperture Values and Depth of Field
Many things can be simulated in the lab under controlled conditions. However, my favorite laboratory is nature with its wild inhabitants. There are more dynamic environments and conditions that are impossible to replicate. Nevertheless, it shows how something like depth of field really looks in a photo and how it impacts the artistry of photography.
When I took the photos below, I tried to keep the number of variables to a minimum so that you could focus on how each different aperture looks. I photographed each bird from a tripod and therefore from the same distance, with the same 500mm f/4 lens, and against an identical background. The only major change was the aperture used. All photos are without cropping and, unless otherwise noted, without denoising and local adjustments.
Let’s start this series with this Crimson-rumped Toucanet, which inspired me to write this article in the field. With the lens wide open, the background is beautifully separated, but only the head of the Toucanet is in focus. The tail is within the depth of field by f/11. With each step toward f/22, the background becomes more distinct and distracting. (I had to raise ISO to compensate for the narrower apertures, so the noise also increases.)
Here’s how the progression of photos looks. Note that I included f/6.3 even though it’s only 1/3 stop slower than f/5.6, since many of today’s telephoto lenses have a maximum aperture of f/6.3:
For reference, here’s how the first photo compares to the last:
NIKON Z 9 + VR 500mm f/4E @ 500mm, ISO 180, 1/125, f/4.0
Unfortunately, the Giant Antpitta didn’t allow me to go narrower than f/8 before flying away. Still, it’s interesting to study how the lens handles a much busier background:
In this case, the final photo imitates the kind of subject separation you could expect from a slower zoom, such as the Canon RF 100-500mm f/4.5-7.1 L. As you can see from the example, even f/4 can’t work wonders if the background is too close to the subject. But there is still a clear progression from more to less separation.
Now for something a little different. Aperture is not the only thing that affects your depth of field. So does your focal length. And thanks to the Auto Capture feature on my Nikon Z9, I was able to set up a photo with this Antpitta at a 65mm focal length! Thanks to this, you can compare the following pair of photos taken with the same camera, same f/7.1 aperture, and approximately the same size of the bird in the photo.
The photo taken at 500mm substantially magnifies the size of the out-of-focus background. This clearly helps with subject separation. However, I should mention that you aren’t technically gaining any more depth of field on your subject with the wider lens. If you look at the stump the Antpitta is standing on, suddenly you see that the same region is out of focus both times:
What’s the practical lesson here? Simply put, the background will appear different with a wide-angle lens and a telephoto, even when the depth of field is technically the same. This is an advantage to telephoto lenses if you want to get more subject separation at a given aperture.
Let’s move onto another examples. The male Masked Trogon seems to know which aperture suits him best. When photographed at f/4 and f/5.6 he showed the camera his beautiful red belly. At f/6.3 through f/11, he turned around on the branch to show me a disinterested look, plus a blood-soaked tick on the side of his face. He didn’t let me shoot at the narrower apertures and flew away. I can only agree with Trogon. I also think that f/5.6 offers a balanced mix of depth of field and subject separation. What about you?
So far I’ve shown you fairly large birds, from blackbirds to pigeons. But smaller birds require you to get much closer. In the case of hummingbirds, I reached the limit of my lens’s close-focus capabilities.
In this case, I was dealing with two conflicting goals. I wanted a sharp image of the hummingbird, including details of its nest, while suppressing the complexity of the surrounding environment. The optimal aperture is therefore a work of compromise. Note that even at the extreme aperture of f/22, the depth of field is still quite shallow.
In this case, for telling a story, I prefer the range from f/5.6 to f/8. The maximum aperture of f/4 just leaves the subject a little too blurry.
In the last example, we approach another small subject at the close focus limit of my camera. Although the Empress Brilliant is one of the larger hummingbird species, it will hardly fill the frame.
Photographing hummingbirds is a kind of action macro photography. You’ll be focused so closely that even a moderate aperture will give you a very shallow depth of field. For this particular image, I would consider an aperture of f/8 to be optimal. (Although hummingbirds sometimes force you to shoot at maximum aperture so that you can use a better shutter speed.)
Even an aperture of f/11 isn’t quite unusable. So in theory, you could take the Canon RF 600mm f/11 IS STM lens. But its minimum focusing distance is 4.5m, which can be limiting for this type of photography. However, I’m more concerned about the reliability of its autofocus, which would have to deal with a really small amount of light.
Conclusion
In the examples above, I’ve demonstrated a range of situations where your choice of aperture has an important effect on the photo. And it wasn’t always the photo taken wide open at f/4 that I preferred. Of course, there are situations where an aperture of f/4 or even f/2.8 is literally priceless with exotic prime telephoto lenses. However, even slower lenses with apertures of f/5.6 or a bit slower are not out of the question. Especially for smaller subjects, you may need to stop down if you want your subject to have enough depth of field.
Of course, you’ll still run into other compromises like autofocus performance and the ability to shoot in very low light. But with the better autofocus systems and high ISO performance of today’s cameras, plus better noise reduction tools, those considerations are less significant than ever.
Finally, I want to highlight that you don’t get any extra depth of field by using a shorter lens and then getting correspondingly closer to your subject. In both cases, the magnification of your subject is the same size, so anything that’s out of focus in one photo will also be out of focus in the other (even though the background will look substantially different). If you need more depth of field on your subject itself, using a narrower aperture is the best approach. You could also back up or zoom out so that the subject takes up a smaller amount of space in the photo.
If you’d like to learn more about depth of field, there are several resources on Photography Life where you can expand your knowledge. For example, you can read Understanding Depth of Field – A Beginner’s Guide by Elizabeth. Then you can move on to Spencer’s Depth of Field Myths: The Biggest Misconceptions or Hyperfocal Distance Explained.