nebraska focus racking

[Ray Equis]

just watching nebraska again. i wonder if this shot is solely focus racking or a change in aperture as well - 0:51-0:54

- do you calculate this in advance or is it just trial and error?. whats up with the image compressing laterally when the focus changes back to the front seats?.

[David Mullen ASC]

I don't think there is an iris rack though in the D.I. the colorist may have tried to pull a little bit of overexposed detail down once the focus shifted to the background, but I didn't really see a change.

 

The stretching laterally is an artifact of classic rear-anamorphic prime lenses. Early CinemaScope lenses had a problem where when the lens was focused to near minimum, the amount of optical squeezing was decreased to less than 2X, but in projection, with a constant 2X lateral stretch, those shots, mainly close-ups, looked fatter.

 

So Panavision solved the problem of "CinemaScope Mumps" but it meant that to keep to point of focus at a constant 2X horizontal squeeze, the out-of-focus areas would get more than a 2X squeeze, so they look skinny even after the image is stretched back out laterally by 2X. So when you do a focus rack, you see the amount of squeezing shift as a form of lens breathing. The only way to minimize it is to stop down the lens a lot to reduce the amount of frame that is out of focus.

[Ray Equis]

thanks david nice background info!