Defining breathing

[JW Lee]

I hear breathing talked about here quite a bit and I was wondering what the true definition is. How can you qanitify it in real world terms. Being a video guy, I'm still getting up to speed on primes.

[Brook Willard]

Breathing occurs when you rack focus on a lens and the apparent focal length shifts. That is, shifting the focal plane makes the lens appear to "zoom in" or "zoom out" a little.

[Evin Grant]

here you go.
http://www.evingrant.com/breathtest.gif

[Jaime Vallés]

Is it just me, or is breathing something really, really minor that only the well trained cinematographer would notice it's even happening? I mean, seriously, how many rack focuses in a row would you have to make to call attention to the lens breathing? If the above picture is an example of "bad" breathing, then I sure as heck don't mind spending my limited cash on owning a great set of Nikon lenses instead of renting Cooke lenses!

Just curious... Do the DVX, HVX, HD100, Z1 and XLH1 show any signs of breathing? Or did they compensate for that when making their lenses?

[Evin Grant]

The HD100 lens breathes a bit the others use the Chip block to focus, except the XL and so it's minimal.

[JW Lee]

Cool, thanks.

[Chris Gearhart]

If I recall right, the HVX compensates by moving the element itself, but I could be wrong.

I'm with you, though, Jamie. Evin's tests don't look as bad as the bad breath I've smelled before. Maybe Nikon glass and a bottle of Scope is all I'll need until RED primes come out.

[Brook Willard]

High-end lenses have floating elements to combat breathing.

As a cinematographer type, I have no idea if the normal public notices. That said, significant breathing will make me cringe. At the very least I could see it jarring the whuffo audience out of a moment... even if they don't know why.

[S. Um]

Audiences are used to seeing zooming (either by a zoom lens or by dolly), so they might just mistake the breathing for a zoom.

[ericyoung]

If it was really distracting, I think potentially you could reduce or eliminate the apparent breathing with a bit of post-production counteractive zooming? With all pixels we've got to play with in a Red, a little zooming in post shouldn't be too destructive.

[Evin Grant]

And it should only be noticeable on very long focus pulls.

[_BK]

Breathing also becomes a major issue if you plan to integrate any CGI into the footage. Trying to 3D track a camera zoom is hard enough... Trying to duplicate the very small focal length shifts caused by breathing is extremely difficult, if not impossible.

[Stephen Williams]

Hi,

I find breathing is worst on 2/3 inch video zoom lenses. Cameras with fixed lenses are not true zoom lenses but varifocal lenses. Focus and image size changes during 'zooms' are corrected by the motors in varifocal lenses.

Stephen