You've probably heard of lens, or focus, breathing. Videographers love to talk about it, but it can be important to still photographers as well. So what is it? In this video we explain what 'breathing' is and why it matters.
Focus breathing with the Nikon 105mm 2.8G in Helicon Remote / Focus drives me nuts. This is for deep stacks of scale models - 350mm to 1500mm focusing range in one stack (too deep for a focus rail). The old Nikon 60mm AF and DX range are better.
Focus breathing was never a problem when doing close-ups with my focussing rail. A macro lens corrected for focus breathing is indeed a simpler way and not restricted by cumbersome equipment. I don’t do video but I can sure see the advantage of a steady picture angle. Thanks guys for reminding me of these new lenses.
What I got from this video: when doing focus-stacking, focus on the near field first, then work your way back to the far field. This way, you won't lose your filed of view, though you may gain some.
Thank you Chris and Jordan. As always educating. But honestly, as it was never a problem so far, I will not go and spend a lot of time to test my lens park, whether I could detect this phenomenon.
Small tip when testing a lens for focus breathing: stop it down, so that most of the movement that you see when moving the plane of focus is the actual change of angle of view instead of the change in blur.
If focus breathing is such a big deal, (And I for one think it is because I do focus stacking from time to time.), it would be real sporting if DP's Lens Hub database noted this characteristic or lack thereof. Wouldn't it?
Generally, no still photo lenses are corrected for it. If you use a lens, where the entire lens is moving, they all have exactly the same breathing. For focus stacking the stacking software needs to resize the images.
Note, that you can do stacking of macro, either by focusing the lens or moving the entire camera. Moving the entire camera, for macro, also means breathing.
Note, to preserve the perspective while doing focus stacking macro, you should really keep the lens still and move the camera body. Otherwise you get strange halos. This will also have focus breathing.
@Roland Karlsson Yeah but it's not a binary thing (yes/no), it can be measured. In theory it could be pretty handy to know which lens has more/less, short of buying dedicated video lenses.
@LB - yes, it could. But, for lenses with inner focusing it is a rather complex effect, not easily described with a number. And for "normal" lenses, it is exactly the same for all lenses (of the same focal length).
Well, since the main issue IRL is "close reach" with long lenses, I think a couple of samples (min focusing, middle rabge) for a couple of FL (including of course max FL) could be a start.
In a forum I sometimes visit, there's a specific lens which often comes up (OMG max FL isn't what it's written on the box!), despite being known for presenting this phenomenon in quite a marked way.
I was thinking X=distance, Y=diagonal FoV, with multiple plots at different FLs, but that's probably overkill :-P
It's something i watch out for in many lenses, but most lens reviewers never cover this aspect of the lens they reviewed. Minimal breathing is acceptable but if it's severe, it's very likely i won't buy it because my workflow often involves focus stacking. In severe examples, it's almost impossible to align shots and clone affected areas.
Focus breathing is not new and not a digital thing, also, the focal length of a lens is only correct when focus to infinity especially on zoom, so that a tele may not pull things as close as you expected since it has a shorter focal length at close distance, unless it is a tele-macro lens that gives higher magification ratio at close distance, and most zooms are not true zoom the focus keep changing while you zoom... there are some basic knowledge in photography rarely mentioned these days, most people are trying to make things prefect via digital, and frankly I don't like that, I am sort of 'purist' do not rely too much on digital excepted that it saves time and money.
I think you've just installed a new demon in heads of many photogs who, up till now, didn't care/see ... for many it will be educational and important. for some, Just like in the story about watching red cars and seeing more and more of them, destroying :D
Can the camera uses automatic digital zooming synchronised with the lens to overcome the focus breathing problem? I think this would be a cheaper solution.
1. Most lenses do not have digital zoom. 2. I think the digital zoom is not all that precise. 3. Lack of information on exact zooming and exact focusing.
a basic method of controlling it in prime lenses is actually reducing a bit the focal length as the lens focuses further. So yes, as Roland pointed: if the lens would have a precise and smooth control over zoom, it could provide some significant help in fighting the issue.
One of the technique in photoshoot is to take a deep breath. Hold breath for 2 to 3 seconds. Slowly but surely the pointing finger pressing the shutter button.
Yes, absolutely. And the longer you hold your breath the less it hunts for focus. It also prevents shutter shock - but only if you don’t hit the shutter button.
Back in the days of film camera we never had these issues. Yes, we had but never knew it even existed. I don't carry magnifying glass or place pictures under a microscope. I look at pictures at viewing distance
This is not a big deal. I focus first so this matters very little (if at all) to me. I seriously doubt a viewer watching a movie would ever notice. Actually a little focus pull breathing can add to the effect.
I wonder. Zoom cine lenses normally have two gears, one for zoom and one for focusing. It is theoretically possible to take a non corrected lens and make it breathing free by, in sync, turning both gear wheels. Does such equipment exist?
Very nice video, explaining breathing. Now, focus breathing has really two definitions and related to those two problems.
DEFINITION 1 - THE VIDEOGRAPHERS VIEW
This is the one described in this video. That is when the size of subject changes when you focus. That is also the most useful view IMHO. Both for videographers and still photographers. Note that even a simple lens where you move all lens elements as ona package has this breathing, and needs to be corrected for.
Here a non breathing lens is one that do not change focal length when focusing. One where a 1:1 macro has half the coverage as at infinity, so you can use the lens formula when calculating focusing. This always (?) means a lens where you focus the lens by moving the entire lens. This lens will then breathe according to videographers, of course.
But the main problem here is lenses with inner focusing. Lets say that you buy a 100 mm macro lens with inner focusing. But at 1:1 it acts as a 70 mm lens. Is it then a 70 mm macro lens? With regard to focal length it, kind of zooms when focusing.
I once read a 70-200 mm zoom comparison. There they did test the actual maximum focal length at 2 meter away. And it varied from lens to lens. So, at 200 mm, the image size was different at 2 m away. So some had better reach, which might be important, if you are hiding and the bird is 2 meter away.
It kind of kills part of equivalence. "On MFT you MUST use a 25mm lens to get the exact FOV as a 50mm lens on FF. " Not so fast cowboy. If there is focus breathing you likely won't get the same FOV. I've seen some 50MM FF lenses look closer to 85mm for close ups. So just use the lens you like and don't obsess over trying to match one on another system,
A 25mm lens on MFT and a 50mm lens on FF if focused at the same distance assuming its not anywhere near macro distances will have a nearly identical amount of focus breathing. Therefore in normal shooting (head shots to infinity) the result should be rather quite similar to the point where you need to be anal to spot the difference.
“In summary, the proof of equivalence is valid for a traditional-focusing lens. The proof is also valid for an internally focusing lens provided the “new” value for the focal length f is used in the bellows factor and AFoV formulae after focus has been set.
[…]
Although the effects of focus breathing are likely to be similar if the lens designs are similar, a general formula for the change in focal length that may occur when using an internally focusing lens does not exist because any change in focal length away from the value marked on the lens barrel depends very much upon the complexities of the specific lens design. Unfortunately, such information is not commonly reported by the manufacturers.”
I never really understood why people are always looking for the "equivalent" FL for less than FF sensors. I understand how it makes it easier to visualize the FOV, but you are right: it really comes down to how the image looks.
@The Name is Bond Re:” no one really reviews or acknowledges that aspect.”
Not true for high end cinema/film/video gear oriented sources.
In still photography, the valid point has largely been ignored, since you seldom zoom while exposing a single image (if you do, focus breathing is probably the least of your - ahem - issues ;-)
Focus breathing shortens the focal-length at closer focus distances. Rendering a 200mm zoom more like 135mm, which is not what I'm looking for at all as a cheaper way to get better headshots without forking out a ton of cash.
You're better off with, for instance, the 70-200mm MKI Canon f2.8 which doesn't have this issue.
@The Name is Bond How do you know, that “You're better off with, for instance, the 70-200mm MKI Canon f2.8 which doesn't have this issue.” applies to me?
You, personally, may find this important. And I do not deny, that others may also do to some extent, but how many find it that important, when economy comes into play. There’s no lack of lenses with minimal to near non-existing focus breathing, but for many still image creators, the choice is whether they can afford a given zoom lens - with some focus breathing - or not (with next to no breathing). If they have a choice at all with their preferred lens mount.
The problem exists, but in the “big picture”, how important is it for most still photographers, that the focal length shortens, when focusing at close distance?Can it be solved by moving a few inches nearer than 5 feet? On the other hand: For some video shoots focus breathing may be devastating. Maybe not for viewers, but the money-people may have views on minimum quality.
For headshots the difference between 135mm and 200mm can be marked depending on face-shape. It's a technique used by model shooters for maximum face flattery. Try googling headshot 200mm. I generally shoot at 350mm equiv for headshots, roughly 3.5 meters away. (ie, moving closer doesn't solve the problem, it is the problem).
Since one of the uses of a 70-200mm f2.8 is going to be headshots, the breathing issue is important to portraitists such as myself. The concerns you write of are not of any concern to me.
Something not obvious is that very expensive cinema lenses, ones that cost more than a new car, are actually slightly ZOOMING without you knowing to compensate for the apparent change. An Arri engineer mentions it in this interesting video: https://www.youtube.com/watch?v=q1n2DR6H7mk
In the past breathing for video was just accepted. I've made a video thirty years ago with the then famous Angenieux 12-120mm. And one shot particularly showed the breathing effect. Nice shot. For lens constructors it will be tough to make lenses without breathing.
The "cheaper" Zeiss cinema lens prime series have plenty of focus breathing cause they are very close to the photo lenses. I'm sure many productions got great results with them 😊
Great video. I think I always have to rack my brains when i hear that term, and i finally understand that the angle of view changes when you focus. Won't affect me much, since I don't enjoy the significant time it takes to process video, but good to know.
To be honest - in many circumstances I like a little focus breathing! It makes the scene more "dynamic", like a micro dollyzoom effect.
Yes you can't control it and of course it drives serious cinematographers crazy :-) but not every scene is disturbed or destroyed with some focus breathing.
Also take a look at all of Nikon’s Z lenses. They are all optimized for video with little to no focus breathing. The Z 70-200 S is also almost parfocal! They are really outstanding for video.
Please don't get them started on T-stops. If the typical DPR visitor finds out his lenses are a third- to a half-stop less bright than advertised there will be a monthslong freakout—especially when he finds out how his camera's metering system accounts for the difference. And besides, if you tried to fix the situation you would wind up creating a problem where there was none before.
If you use an external light meter, then knowing the T-sop is useful. And pro cine folks do generally use an external light meter or have artificial light with known strength.
Yes Roland but that is a problem that solves itself. If you know how to use an external light meter then you have already memorized the difference between the nominal and actual f/stop values for all your lenses and the amount of compensation you need to dial in. There have been a couple of people who say they have evidence that DSLRs already do the f/stop compensation automatically so it’s not an issue there either.
Either way it would just be another opportunity for the equivalence people to spread their poisonous half truths.
MrBright. No, I do believe very few have any clue about the loss in their lenses. So, they will under expose, given an external light meter. Or maybe they cannot use it :)
Anyway, this solves itself in DSLR cameras because the light meter measures light coming out of the lens.
Exactly. I often use an incident meter with my Nikons and the exposure is always exactly what it should be which indicates to me that Nikon might be making minor modifications in shutter speed or ISO to account for the slightly smaller-than-stated aperture. But you know what, I’m happy that they do because that’s their job, removing trivial technical Issues from my sphere of concern.
Maintaining a constant angle-of-view actually requires lenses to reduce their focal length with closer focus. Simple fixed primes always reduce their angle-of-view when focused closer.
It'd be very useful if DPR would maintain an online list of best and worst lenses for focus breathing. Or perhaps someone reading this is aware of such a list somewhere and can share a link? (Of stills-oriented lenses. True "cinema" lenses tend to be priced above what I can afford or justify spending on a lens.)
That doesn't seem very useful as you'd be mixing primes and zooms of completely different focal lengths plus you'd get into discussions like whether it's better to have a f/1.4 lens with more breathing than a f/2.8 lens that can't focus at f/1.4 at all. This looks like the kind of feature you look at after you've narrowed it down to 3-4 apples-to-apples lenses, at which point the latest review probably compares it to the most relevant alternatives.
What KjellRS said. From my experience of video and cinematography, a difference in colourimetry, bokeh and general rendering between different lenses is much more noticeable than a bit of focus breathing on the occasional focus pull. That's a major reason why cinematographers tend to rent lenses in matched sets. Plus it's been a feature of video for so long it would have to be very obtrusive (or the material very boring...) for the average audience member to notice. Nice to get rid of it if you can, but it's not the end of the world. Except to Jordan, apparently... ;-)
Focus hunting is an act of the camera unable to obtain focus easily on a subject so the focus will rack back and forth trying to find enough detail/contrast to lock onto. Focus breathing is the change in field of view as you change the focus from near to far or far to near. In the extreme a macro lens may be a 100mm lens when focused at infinity but only a 70mm lens when focused at a 1:1 magnification distance.
No, they're different things. I can't give a perfect definition, but I think it's safe to say that focus hunting happens when the camera is not able to lock focus or at least not quickly enough, and the focus goes back and forwards before finally locking on the desired subject/object. Focus breathing, on the other hand, is a change in field of view that occurs while the lens is focusing, and is more evident when going from the minimun focusing distance to infinite (it's as if the lens was "zooming" or changing focal length while focusing). This being said, it's perfectly possible that both things happen at the same time, hence the confusion.
Focus hunting = poor autofocus not settling. Focus breathing = focal depth changes focal length. It's a natural consequence of moving the glass inside the lens, what breathing corrected lenses do is actually to zoom a little to compensate so the net result is zero.
Unfortunately, the explanations above are almost exactly OPPOSITE to what actually happens!
Consider a lens which focuses by “moving the whole body” w.r.t. the sensor. Its focal length ƒ — obviously — does not change. However, as you change the focal distance near↔far↔near, the FIELD OF VIEW changes (image the ray geometry in a peephole lens).¹⁾
¹⁾ To be precise: a point in focus becomes a bokeh circle when going out of focus, its size changes as you focus. “Focus breathing” means that the CENTER of the bokeh circle MOVES when you change the focal plane.
To avoid breathing, this should be “compensated by zooming a bit”. Essentially, the lens should “be a zoom lens”, and it SHOULD slightly CHANGE its ƒ (in a controlled fashion) when changing the focal distance.
So: (essentially) breathing ≈ ƒ does change. No breathing ≈ ƒ changes (in a precise manner!) when you change focal distance.
(I have no clue why this is not done electronically on “real” zoom lenses — with power zoom.)
There's another effect of focus breathing that does matter to photographers who are into close-up and macro photography! Using a lens that has strong focus breathing, they may need to get much closer to the subject to get the same field of view, even with the same nominal focal length, than with a lens that hasn't.
No where near ideal but frame wide and crop differently for each frame as you're editing the video. I don't shoot video so I don't know if there are other options but this is what I could come up with after a few moments of thought.
It doesn't matter if you manually focus or use autofocus, if you change the focus distance then the field of view will change unless you pay big money for a lens that has this well corrected for. I suppose you could leave the focus distance the same and move the rig back and forth but that is also very far from ideal.
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