Focus Breathing may be a phrase that is hard to imagine and understand when you hear it for the first time. ‘Breathing’ ? …what does that have to do with the focus of the camera? That is exactly what I thought when I first heard of the term. Don’t worry too much! It is not that hard; in fact it is fairly simple and easy to understand.
If you have been a photographer for a little while now and have used a few lenses, you have probably faced focus breathing on your own; perhaps you did not notice it. Okay then let me define what focus breathing actually is. Put very simply, focus breathing is the tendency of a lens to automatically zoom out when changing focus from infinity to a close subject or vice versa. Still confused? Okay let me give you an example, you can follow along if you want, this is pretty easy, it will help you understand the inner mechanisms of the problem.
Set up your camera on a tripod and attach any zoom lens on it. Now set the zoom to the lowest focal point the lens would allow and then change the focus from infinity to absolutely the closest the lens would allow. Do NOT touch the zoom ring during this process. Now, do the same thing again but with the longest focal point. Zoom out the lens as far as as it would allow and then again rotate the focus ring so that the focus changes from infinity to close. Did the composition of your frame change automatically without you touching the zoom ring when you re-focused your lens? If it did, your lens suffers from focus breathing.
Let me reiterate the point one more time. Generally, all lenses DO perform at the same focal length that they are advertised as, when focusing at infinity. The problem arises when focusing close, the lens automatically starts to zoom out on its own. This might happen with any make or model of lens. As you can see in the video below, even the holy trinity of Nikon lenses ( Nikon AF-S FX NIKKOR 14-24mm f/2.8G ED, Nikon AF-S FX NIKKOR 24-70mm f/2.8G ED, Nikon AF-S NIKKOR 70-200mm f/2.8E FL ED VR) have the focus breathing problem.
I do use the word “suffer” but it really isn’t much of a deal for us photographers. If you now go through all the lenses you possess, you may find that many of your lenses including primes lenses have a certain degree of focus breathing but you haven’t noticed it yourself. The reason is self-explanatory, it is pretty easy to avoid and go around this problem. You can just change the distance between you and the subject and the try and get the same composition.
Focus breathing for filmmakers:
Focus breathing may become a real problem when shooting a video since that may not be avoided so easily. Imagine a scenario when a scene requires the focus to gradually shift from a person far away to a subject very close to the camera. If during the refocusing part the composition of the entire shot changes, the video would look really bad and choppy. Hence, film makers use lenses that have next to none of the focus breathing problem.
Zoom Vs Prime Lenses:
When I first heard of focus breathing, I was nearly certain that this would always happen to zoom lenses as only they have the capability to change focal lengths. Prime lenses are fixed lenses and hence, do not change the focal length during the shoot at all. But I was wrong. Some prime lenses did exhibit small but noticeable amount of focus breathing when put to the test.
The reason is this. No lens for a DSLR consists of a single piece of glass. Most of the lenses have a few optical lens elements that together make up a lens. When you focus your camera onto a subject by turning the focusing ring, the lens elements move within the lens to achieve the desired focus.
If you have your camera nearby now, grab it and you can see this for yourself.
Open the lens cover and just look at the front of the lens. Gently rotate the focusing ring so that the lens is set to infinity focus and then turn the ring slowly so that the focus returns to the closest focusing distance. You will notice that as you focus nearer and nearer, the lens elements juts out more and more.
The lens optics have to move away from the sensor to get the close subject in focus (it is also the same reason why during macro photography you may use a extension tube to allow close focusing, all you are doing is increasing the space between the lens elements and the sensor of the camera). In many of the inexpensive kit lenses, you can actually see the lens physically jutting out. What I am trying to explain is, to get a subject in focus that is at a specific distance form the camera, the individual lens elements have to realign and maintain a certain distance from each other . Sometimes when the internal lens elements move and try to get the desired focus, the composition of the frame may change, this is the problem of focus breathing.
Now, naturally zoom lenses have substantially more lens elements than a prime lens and hence, they are also more susceptible to focus breathing; but it is NOT the case that only zoom lenses have this problem.
The Nikon 70 mm to 200 mm lens (which is mega costly) only manages to be around a 135 mm lens when shooting at a full 200 mm; whereas the Canon 70 mm to 200 mm performs better at around 150 mm. As I said earlier, this doesn’t matter most of the time since you as the photographer can always move in close to the subject and get the same composition with the focus. It only does matter when the distance cannot be bridged/altered like when you are on a focus stacking shoot or maybe when you are shooting video.
If you understand the root of the problem, the solution is also pretty easy to guess. The basic problem of focus breathing is that the lens steals from the focal distance when trying to focus at a distance. So, in theory, if we could manage to add a little distance between the lens and the cameras sensor, this problem will we solved. That is exactly the solution to this problem. What we can do here is add a few extension tubes and see if that solves the problem. The extension tubes would definitely help focus closer and make the ‘breathing’ as low as possible but use it with caution.
Just remember that extension tubes do have side effects of not being able to focus at infinity, so use them only when you have to use the lens at its longest focal length but have to focus at the closest.
Good luck then. Hopefully now you can focus closer!