What is focused breathing in a camera lens?

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Focused breathing is a term often used when discussing the features and specifications of a camera lens. This is a problem that occurs on a wide range of lenses and can negatively affect your photography and videography in certain situations. In this article, we’ll look at what Focused Breathing is, the situations it affects, and how you can avoid it.

Contents

What is Concentrated Breathing

For starters, what is focused breathing, anyway? Also known as “lens breathing,” it is about lenses and how they magnify images at different focusing distances.

Focus breathing refers to when the focal length of a lens changes subtly (or noticeably) as the focusing distance changes.

Zoom lenses and prime lenses exhibit this behavior to varying degrees. One way to see this for yourself is to frame a scene, then change your lens focus from minimum to infinity and pay close attention to the edges of the frame – you may notice that the shot of view seems to “zoom” in and out very slightly as the focal length changes.

You can also take two shots keeping everything the same and just have the subject in focus at infinity in one case and minimum focus distance (MFD) in the other. You will notice that there is a slight difference in the focal length (magnification) even though they were taken keeping the same focal length on the lens.

This is an exaggerated case of focus breathing since it increases as the distance between the two subjects in focus (i.e. the focus distance in both photos) increased. Magnification and angle of view change, giving us an apparent change in focal length.

A visual example of focused breathing

In the two sample photos below you can see that as the focus is changed from the moving mount in the foreground to the mirror mount in the background, the second image appears to have been magnified and a slightly cropped (they were not cropped post-production).

A photo with a close focus distance.
Without moving the camera or adjusting the focal length, the focus is adjusted to another plane. Notice how the composition has shifted slightly around the edges of the frame due to focused breathing.

Here’s a GIF with the two photos alternating – notice how the angle of view and magnification change slightly when only the focus is adjusted:

Why Focused Breathing Happens

Focus breathing occurs because most modern camera lenses typically use an internal focusing system. In these lenses, if we change the focus of the lens manually or with autofocus, the front of the lens element and the lens barrel do not move or rotate, which means that only certain smaller lens elements inside the lens barrel need movement.

The lens focus group in a Nikon lens diagram. Artwork by Nikon.

This type of internal focusing system has a number of advantages including portability (smaller and lighter designs), faster focusing (due to smaller set of focusing elements) , compatibility with some lens filters and lens hoods (due to front lens element not rotating during focusing), and constant lens length (front element does not extend during focusing, especially useful in macro photography).

The trade-off, however, is focused breathing. Focusing on internal focusing lenses causes the internal element to move independently of other lens elements, causing a slight change in focal length.

There is a balance between how quiet and optically perfect the lens is and how much focus it presents. It comes down to the design and construction of the lens and is also reflected in the price. So cinema lenses have the least amount of focus breathing (or virtually none at all), but are priced much higher than a photography lens designed primarily for stills.

Problems caused by concentrated breathing

The reason cinema lenses need to eliminate focused breathing is that this phenomenon is clearly visible in videos and can be a big distraction. You’ll also notice that two lenses with the same zoom range and aperture can be labeled as cine and non-cinematic lenses, and focus breathing is one of the characteristics that differ between the two (among other things).

One situation where focus breathing can affect stills to some extent is when trying to focus stack images, especially when shooting with lenses that exhibit a lot of focus breathing. point. A photographer can take multiple images that vary in focus from foreground (MFD) to background (infinity) to keep everything in focus during focus stacking. Thus, the stacked series of images would vary in focal length and magnification, which would cause problems in post-production.

Focus breathing can be a problem when doing focus stacking in macro photography. Photo by Martin Cooper and licensed under CC BY 2.0.

Newer versions of Photoshop are able to handle slight edits when stacking images. Due to focus breathing in lenses, you have to crop the final stacked image even if the images were taken on a sturdy tripod.

Avoiding Concentrated Breathing Problem

So how do you eliminate or at least reduce focus breathing artifacts from photos? The simple answer is to upgrade or buy a lens that doesn’t feature Focused Breathing, because that’s a property of the lens, not how you use it. But you can still try to narrow it down by using your existing lens in certain ways.

Since focus breathing is most pronounced in a lens for two shots taken at extreme focal lengths (one focus at infinity and one focus at minimum focus distance), you can try to reduce this distance and take pictures in which the subjects are almost the same distance from the lens so that you don’t have to change (or at least minimize the change) the focus as much between shots .

Most lenses made for photography, including high-end lenses, don’t clearly indicate if the lens suffers from focused breathing, so it becomes difficult to buy lenses and do a side-by-side comparison if this is an important optical problem. to your particular photographic work. If the magnitude of focus breathing is not listed for an objective or combination of objectives you want to compare, you can look at the maximum magnification factor (mostly indicated as 0.15x, 0.25x, 0 .38x, 0.71x, etc). The higher the magnification factor, the less the lens suffers from focus breathing.

The other way to compare two lenses to check for focus breathing issues is, as previously described, to take real-world photos with them (on a tripod) and see how magnified the images are. Take two shots, one on an object that is at or near the minimum focus distance of the lens and the other at infinity and repeat this for the other lens or lenses. The phenomenon is clearly visible on the edges if it is present.

Should You Care About Concentrated Breathing?

The last question arises here. If and to what extent you should care about focused breathing. As stated earlier, if you shoot video or plan to do so, Focus Breathing should be an important factor in your lens choices. This shows up clearly in a video if the focus changes in the same scene. These can be slightly corrected with modern video editing software, but these can make the video jittery and unprofessional.

On the other hand, if you’re using the lens primarily for stills, focus breathing usually won’t make a difference except in certain situations like focus stacking or photos used in scientific studies. . Even if you try to compare photos taken with a lens with high focus breathing and a large distance between the subjects in focus between the two shots, it’s very hard to see the problems unless you look at the edges of the frame.

Additionally, photographers typically recompose photos on the fly as they change focus, allowing the final composition to always be what they intended to capture.

Ultimately, focus breathing shouldn’t matter much to you unless you’re primarily into video, but at least now you’ll know why two frames of the same camera setup and settings may seem a little off.


Picture credits: Photos from Depositphotos

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