Film gate

[tricky]

I notice that when I create a Vrayphysical camera, the default film gate is 35mm.

With max cameras, it is 36mm.

In order for you to match a photographic background (when converted to 35mm equivalent, in our case, as we are using a Canon EOS 350D, we multiply it by 1.6) with a model and a vray camera, the film gate needs to be changed to 36mm.

We have only just found this out.

Any reason why Vray cameras are set to 35mm rather than 36mm?

And for that matter, why is 35mm photographjy called 35mm photography when in actual fact it is 36mm photography?

Or am I being stooopid???

[vlado]

I think the confusion comes from the fact that the 35 and 36mm numbers refer to different things and measure different values.

The 35mm comes from the fact the the entire film strip is 35mm wide. Normally, for a movie film, the frames are oriented with the horizontal direction perpendicular to the film width, like in this page:

http://en.wikipedia.org/wiki/35_mm_film

The actual size of one frame is less than 35mm wide.

For still photo cameras, however, things are a little different. The film strip is still 35mm wide, but the actual frames are oriented with the horizontal direction along the film strip, like in this image:

http://en.wikipedia.org/wiki/35_mm_film#VistaVision

So that you end up with one frame being 36 mm x (I think) 24 mm.

Since the V-Ray physical camera is by default set to a still photocamera, I suppose you are right that the film gate should default to 36mm.

Best regards,
Vlado

[tricky]

Thanks for the explanation Vlado. There are so many esoteric areas of cinema/tv/photography its untrue! NTSC/PAL/progressive/fields/aspect ration/pixel aspect ratio/film gate/fps.......the list goes on. I think this, plus gamma are possibly the two most complicated elements of what we do.

10+ years of doing this and I am still not wholly clear!