A question about breathing For Mr. Duclos

[Nick Gardner]

My understanding of why lenses breath is this - A basic lens, is a cell, an arrangement of elements inside a body. This cell is inside a helicoid housing which moves the cell closer or farther from the film plane when rotated. The reason lenses breath is because we are moving it physically in relation to the film plane. An 18mm has a very shallow depth of focus, so it will breath very little as the distance it has to move is short. A 100mm has a much deeper depth of focus, so it must move farther to shift the point of focus.

Now assuming that the above is correct, what types of technologies are employed to counter this effect and how do they work? I have heard the term "floating elements" which I interpret as elements that are not married to the rest in the lens "Cell" as I described it. I also may be completely full of shit and have my optical principles all cattywompus.

At any rate, I would like to hear a technical explanation of breathing from some one who knows better than me. I'm curious about such things ;-)

Thanks in advance,

Nick

 

[Alexander Ibrahim]

I'd like to see a good explanation as well, my understanding is similar to yours. I only have one university course in optics ... and that was just physics - not engineering, so there is a huge gap in practical lens design/theory for me too.

 

[Mike Prevette]

My understanding is basically the same. I think "Floating element" designs use multiple cells, essentially one main unit and then a corrector that moves in the opposite fashion keeping the breathing and aberrations in check.

 

[Les Dittert]

How interested is the Red community in a plugin that automatically removes the breathing effect ? I'm trying to gauge the interest.
-Les Dittert

 

[fALk Gärtner]

How interested is the Red community in a plugin that automatically removes the breathing effect ? I'm trying to gauge the interest.
-Les Dittert

You think thats possible artifact free? Would be awesome for VFX for sure.

 

[Imran Farouk]

How interested is the Red community in a plugin that automatically removes the breathing effect ? I'm trying to gauge the interest.
-Les Dittert

If it were possible, if it were for the right price, if it were to not affect the quality of the footage...

I think there would be a market even further than RED...it would be massive. DSLR peeps would be right on it as would be all RED people who use still lenses. Be a big savings on those just starting out with the Scarlet X and have canon lenses...

 

[Dave Blackham]

Yes interested in an app.....

 

[Alexander Ibrahim]

How interested is the Red community in a plugin that automatically removes the breathing effect ? I'm trying to gauge the interest.
-Les Dittert

Removing breathing is already done in high quality in Resolve, and you can do it manually or automatically.
(Stabilize the zoom)

The problem I think you are missing Les is that it's not a "free" operation. You lose resolution. Depending on the lens and shooting format, it can get quite ugly.

I just did a bunch of these stabilizations on material shot with industrial ENG lenses ... the shots were obviously softer. High end broadcast lenses would solve the problem.

If you are working in 5K for delivery to 4K, then better still lenses, like the Zeiss or Leica Primes probably breath little enough to be compensated for acceptably.

If you are a Scarlet user shooting 4K for 4K post ... you are asking for trouble.

If you are shooting 4K for 2K or 1080p delivery ... you can do this no problem ... but I assume you are shooting 4K because you want to be able to redeliver in 4K when that becomes standard right?

It's smarter to get lenses that don't breathe if you object to breathing.

Also remember ... even if its "automatic" you need human judgement in the process.

In other words, you are taking a perfectly solved technical problem, turning it into a problem that now has to be solved in post hundreds of times.

Fix it in post is NEVER the smart way to approach a problem.

You are being penny wise and pound foolish.

 

[fALk Gärtner]

Just to clarify - if you guys talk about breathing you just mean that when zooming there is a focus difference.

What about the breathing that when focus pulling there is a slight zoom in/out - you wouldn't call that breathing? We observed this on Ultra Primes recently.

Since zooming is rarely done these days in Motion Picture work the first breathing is not a huge problem - the other is a bigger one for 3d integration.

 

[Nick Gardner]

Nope, we are not talking about zooming. If you reread the the first post, it should be pretty clear.

Nick

 

[Quentin Devillers]

Falk, I think we are speaking of breathing in focus pulling.

Nick, I will try to explain (in my bad english) my piece of knowledge about this subject ^^

Master Prime from Zeiss absolutly don't breathe. Because, in fact, there is "floating elements".
When you focus you move somes of the elements a litlle, so your 50mm become a 48mm when focusing close...
In fact, to avoid breathing we have to optically correct the "natural" changement of angle of view.
So "floating elements" means that all the glass elements are not moving the same way.
When your focusing some elements move in a way while others move in an other way (or same way but not same speed, I have to check this).
So the Master primes zoom a litlle when you're focusing closer, to compensate the breathing.

Hope it can help.

 

[Imran Farouk]

Just to clarify - if you guys talk about breathing you just mean that when zooming there is a focus difference.

What about the breathing that when focus pulling there is a slight zoom in/out - you wouldn't call that breathing? We observed this on Ultra Primes recently.

Since zooming is rarely done these days in Motion Picture work the first breathing is not a huge problem - the other is a bigger one for 3d integration.

Falk, I think we are speaking of breathing in focus pulling.

Nick, I will try to explain (in my bad english) my piece of knowledge about this subject ^^

Master Prime from Zeiss absolutly don't breathe. Because, in fact, there is "floating elements".
When you focus you move somes of the elements a litlle, so your 50mm become a 48mm when focusing close...
In fact, to avoid breathing we have to optically correct the "natural" changement of angle of view.
So "floating elements" means that all the glass elements are not moving the same way.
When your focusing some elements move in a way while others move in an other way (or same way but not same speed, I have to check this).
So the Master primes zoom a litlle when you're focusing closer, to compensate the breathing.

Hope it can help.

So...in short, every lens breathes to some degree, some zoom to compensate slightly, others just breathe...

Either way, theres no such thing as a lens keeping as it is, no matter the focus point (like you said Quentin, 50 to 48 instead of 50 to 50) up close or far away.

All that happens is the degree to which the lens maker compensates for breathing? So I take it Leica's with the FLE are pretty good with not breathing (to an extent) in comparison to the versions without the floating element

 

[fALk Gärtner]

Falk, I think we are speaking of breathing in focus pulling.

Master Prime from Zeiss absolutly don't breathe. Because, in fact, there is "floating elements".

Thanks just wanting to make sure we are all talking about the same thing - we are

on our latest project the ultra primes breathed. Look at the edges of the picture - the power sockets for example.

here:
http://protobits.com/secrets/40mm_UltraPrime_Breathing.mov

40mm
fstop: 4
shutter:180
focus pull: 4,7m - 1,2m
4k 16:9 Redcode 36 RedOne

 

[Björn Benckert]

You think thats possible artifact free? Would be awesome for VFX for sure.

Breathing removal could easily be done in redline X if canon glass or LDS is used and lens settings goes into the meta data. Every known lens is then very easy to digitally "de breath" you would loose slightly on the pixel count and your image would need to be rerastered. But the sharpens you would loose doing so would not even be noticeable when the image comes from a 5k or 4k source.

So in a very near future all lenses outputting data will be non breathing... at all. We have done the math and shot grids with the milo and it's very easy to set up. also chromatic aboration can be treated the same way. So bad glass will be not so bad in a near future.

And one more thing. It's quite a lot easier to make a fast lens that does breath heavily so if this is something the lens makers can just skip, and have treated digitally then lenses will not only be cheaper, they will also be faster and clearer.

 

[Imran Farouk]

Breathing removal could easily be done in redline X if canon glass or LDS is used and lens settings goes into the meta data. Every known lens is then very easy to digitally "de breath" you would loose slightly on the pixel count and your image would need to be rerastered. But the sharpens you would loose doing so would not even be noticeable when the image comes from a 5k or 4k source.

So in a very near future all lenses outputting data will be non breathing... at all. We have done the math and shot grids with the milo and it's very easy to set up. also chromatic aboration can be treated the same way. So bad glass will be not so bad in a near future.

And one more thing. It's quite a lot easier to make a fast lens that does breath heavily so if this is something the lens makers can just skip, and have treated digitally then lenses will not only be cheaper, they will also be faster and clearer.

It's not really a one click process though is it? Like Alex said, there is still a need for a human component

This sort of method though will be great when we start getting say 6-8K and shrinking to 4K for delivery then I'm sure this will all work out great, 5K to 4K is a little minor issue but not too big...

I guess I'd prefer it if the lens manufacturers just didn't make us need to do it in post at all...

 

[Björn Benckert]

It's not really a one click process though is it? Like Alex said, there is still a need for a human component

This sort of method though will be great when we start getting say 6-8K and shrinking to 4K for delivery then I'm sure this will all work out great, 5K to 4K is a little minor issue but not too big...

I guess I'd prefer it if the lens manufacturers just didn't make us need to do it in post at all...

Well it would not really need to be a click... I believe the epic has enough processing power to do it internally in the camera. So if the lens data from a know lens is fed to the "brain" then the picture going to the touch screen could already be "de breathed"....

But I guess audio on playback and other more common functions is a bigger priority for the red programers...

 

[Alexander Ibrahim]

Breathing removal could easily be done in redline X if canon glass or LDS is used and lens settings goes into the meta data.

You don't need to have lens metadata.

You can use tracking points.

The simplest example we can all get at is Resolve's stabilizer.

Works perfectly and its available now.

AE's Warp Stabilizer handles this well too.

Every known lens is then very easy to digitally "de breath" you would loose slightly on the pixel count and your image would need to be rerastered. But the sharpens you would loose doing so would not even be noticeable when the image comes from a 5k or 4k source.

Disagree ... because you aren't thinking big enough.

If you are shooting 5K for 4K finishing ... you are really just over 4K in real resolution. Once you start stabilizing the image, it will be notable softer in 4K display.

Now, if you are shooting 5K for 1080p finishing ... yeah then you can totally go to town with stabilization. If I had a 4K scan of Cloverfield I could probably even make that mess watchable in SD or 720p delivery.

So in a very near future all lenses outputting data will be non breathing... at all. We have done the math and shot grids with the milo and it's very easy to set up. also chromatic aboration can be treated the same way. So bad glass will be not so bad in a near future.

I disagree. What you are describing is essentially just moving a part of post into the camera.

This doesn't make your glass better ... and it can't improve overall results compared to just using better lenses in the first place.

And one more thing. It's quite a lot easier to make a fast lens that does breath heavily so if this is something the lens makers can just skip, and have treated digitally then lenses will not only be cheaper, they will also be faster and clearer.

They already do this! Grab a kit lens for DSLR, like the 18-135mm f/3.5-5.6 EF-S that comes in some 7D kits.

The 7D corrects that lens for CA, vignetting, breathing and barrel distortion. It still looks like crap compared to Zeiss lenses which are not compensated for. (And BTW all the L series lenses are also compensated for in the camera body ... which is part of why they show so well for stills) If you were wondering why the Canon cinema primes, which are obviously the L series primes rehoused, cost so much its because they had to make the lens housings and mechanics better to deal with cinema work.

Panasonic ENG cameras do some very good CA correction ... not as nice however as just using a better lens.

For more serious high end work ... its better to leave the image in the camera alone, and let the image be adjusted in post if need be.

Use the best lenses you can ... and then fix that in post if you must.

Let's not get ready to move post into the camera though.

 

[Nick Gardner]

I don't see any reason to "fix" it. It's part of the language of film. It can be very disconcerting to bounce focus in a raking two shot when there is no breathing because your brain gets no cue that something has changed other than the foreground guy went out of focus. On a lot of CG and composite shots, i'll have the CG artist add lens breathing as it makes the shot feel more reel and natural. I'm talking about minimal normal prime lens breathing. What some zooms and some primes do, that is very pronounced, is distracting. I was just curious how the technical challenge is overcome ;-)

Nick

 

[Alexander Ibrahim]

I don't see any reason to "fix" it. It's part of the language of film. It can be very disconcerting to bounce focus in a raking two shot when there is no breathing because your brain gets no cue that something has changed other than the foreground guy went out of focus. On a lot of CG and composite shots, i'll have the CG artist add lens breathing as it makes the shot feel more reel and natural. I'm talking about minimal normal prime lens breathing. What some zooms and some primes do, that is very pronounced, is distracting. I was just curious how the technical challenge is overcome ;-)

Nick

I agree to an extent. I think that breathing is an organic part of films.

I don't seek to actively use it in my film grammar ... but its often there so I must account for it. That usually means being creative and trying to motivate or otherwise use the effect.

My ideal however is to have the lens not breathe ... then if I need movement as part of my grammar I can add it by ::gasp:: moving the camera.

 

[Björn Benckert]

Great to see that somebody else is thinking of this. I got some thoughts on your comments...

You don't need to have lens metadata.

You can use tracking points.

The simplest example we can all get at is Resolve's stabilizer.

Works perfectly and its available now.

AE's Warp Stabilizer handles this well too.

I can tell you from my 15 year as a flame artist, trying to figuring out even the zoom factor from "focus pull breathing" using tracking dots of a moving camera shot might be doable, but it's freaking hard, involves the higher level of 3D tracking. Breathing is not only "zoom" it's a "fisheye" warp thing going on also so to create a perfect flat source with only focus moving involves warping swell, do not think you have it in resolve. But do not know for sure do not use the program.

Having a perfectly flat source however is improving 3D tracking and 3D integration by a lot so getting the numbers out of the canon lenses and have it feed into the meta data is huge for post...

Disagree ... because you aren't thinking big enough.

If you are shooting 5K for 4K finishing ... you are really just over 4K in real resolution. Once you start stabilizing the image, it will be notable softer in 4K display.

Now, if you are shooting 5K for 1080p finishing ... yeah then you can totally go to town with stabilization. If I had a 4K scan of Cloverfield I could probably even make that mess watchable in SD or 720p delivery.

That's true, but for the films I worked on there is always a lot of re racking /cropping and zoom in / pan in scan going on. So even when printing back to negative and such the slight blur you would get from the warp is not to rough.

I disagree. What you are describing is essentially just moving a part of post into the camera.

This doesn't make your glass better ... and it can't improve overall results compared to just using better lenses in the first place.

True the best lens is... usually the best lens... however even the best lens can be technically improved this way. Like some one stated here that the MP's does not breath... well that is far from the truth, it does.



They already do this! Grab a kit lens for DSLR, like the 18-135mm f/3.5-5.6 EF-S that comes in some 7D kits.

The 7D corrects that lens for CA, vignetting, breathing and barrel distortion. It still looks like crap compared to Zeiss lenses which are not compensated for. (And BTW all the L series lenses are also compensated for in the camera body ... which is part of why they show so well for stills) If you were wondering why the Canon cinema primes, which are obviously the L series primes rehoused, cost so much its because they had to make the lens housings and mechanics better to deal with cinema work.

Panasonic ENG cameras do some very good CA correction ... not as nice however as just using a better lens.

For more serious high end work ... its better to leave the image in the camera alone, and let the image be adjusted in post if need be.

Use the best lenses you can ... and then fix that in post if you must.

Well meta data lets you do that.

Let's not get ready to move post into the camera though.

Maybe we can let red output the black and white mosaic that the camera is actually shooting then...LOL.
But personally I like to have at least some sort of representation of a half decent debeayered image on my touch screen... And I actually also like, for client purposes, to have the meta data grading in camera, to be able to see how the picture could look in post, having the lens data there aswell (which we will soon) would be great if it could be used but would not need to be burned in as an actual pixel change.