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xxiii
09-13-2011, 02:50 AM
I was trying to match a camera today, and I noticed that if one selects "size 135 (35 mm SLR)" in the Camera Properties or Render Globals Frame drop-down, it sets a value of 1.0512 inch, which is 26.7 mm. However, the correct value is 24mm (0.9449 inch).

135 film (or a full-frame digital sensor) as used by a typical SLR has a frame size of 36mm by 24mm. (The frame parameter appears to be the height or vertical dimension of the frame).

So am I missing something, or is the dropdown incorrect; and what about the other items in the dropdown? (I've only investigated the 135 option as that was the one I was interested in at the time).

If the dropdown is correct (and I don't believe it is), then what is the extra 2.7mm?

Frame also does not appear to be documented, at least in the online-help.

(using layout 10.1 build 2144)

Hieron
09-19-2011, 04:22 PM
Had the same issue today, so assumed them all to be wrong. (the ones I checked were wrong) and filled in the vertical frame size manually using for instance:
http://en.wikipedia.org/wiki/Image_sensor_format
and conversion to inch

However, if you use a SLR like mine that does not use the full frame for filming (mine goes to 16:9) make sure to accomodate for that as well. Then it all lines up.

I would appreciate LW using (milli)meters in frame size as well. Inches is medieval...

xxiii
09-22-2011, 01:19 AM
I came up with the following table for my personal use as I prefer the same focal-length to always mean the same field-of-view horizontally, and I'm used to thinking in terms of what a given focal-length means on my full-frame SLR.

I'm not sure what the situation actually is in the movie and/or video industries, but I find it difficult thinking of one lens as having multiple fields-of-view (and vignetting/distortion characteristics, horizontally-speaking), which I suppose must be the case when using a lens with a super-35, vs a red, vs a cinemascope camera, or HD video cameras with differing sensor sizes, for instance.

Relative to a 35mm frame (as used by still SLR cameras)
Maintaining same field-of-view horizontally for a given focal-length: Lightwave, set frame according to table:


aspect Frame
1:1 (1 square) 36mm
3:2 (1.5 SLR) 24mm
16:9 (1.77_ HD) 20.25mm
12:5 (2.40 wsmovie) 15mm

Or for an arbitrary aspect ratio:

vsensorsize = hsensorsize * 1/frame_aspect * 1/pixel_aspect

(where pixel_aspect is typically 1 and can be omitted as a result).

(fortunately, the field lets you enter metric if you include the mm on the end, though it immediately converts it to inches, regardless of your preference settings).

I don't yet own one of the newer SLRs that can also shoot video, but I'm assuming the above table will be applicable to them (assuming they just achieve an HD aspect ratio by ignoring (cropping) the top and bottom of their sensors).

I presume the intention of this field is to make the lens focal length setting match the corresponding real-world camera with an equivalent lens, at least when using an aspect-ratio that matches that camera?

Lewis
09-22-2011, 01:43 AM
Send BUG report, something is wrong/weird there definitely.

xxiii
09-22-2011, 09:48 AM
Reported.