[Bf-committers] Blender Film Plane
Harley Acheson
hacheson at shawnigan.ca
Sat May 15 07:03:28 CEST 2010
Hello,
The size of the film plane (image sensor) of the Blender camera is exactly 32 millimeters,
measured diagonally. Sorry if I am stating the obvious, but I’ve never read that anywhere.
The film plane can be directly measured. Set the camera to any field of view and then
note the focal length in millimeters and the FOV in decimal degrees -- the default is 35
millimeters and 49.134 degrees. Then solve for the film plane. Tangent of half the FOV
multiplied by the focal length times 2 is 31.99975 millimeters.
The size of the film plane is not defined in the source, but it is implied by the lens
calculations in “math_rotation.c”. You can take half of the diagonal size of the film plane
of a 35mm camera in millimeters (21.635) and put it in place of the “16” found in
“lens_to_angle” and “angle_to_lens”. Recompile and you will find that the Blender camera
behaves exactly the same as a 35mm camera. A 50mm focal length will now result in a
(diagonal) field of view of 46.796 degrees as expected.
We need to make the diagonal size of film plane into a variable, make it 32 as default,
then allow users to change it on the “camera” panel. Is there interest in this? I would need
assistance with this if I were to attempt it as I am very new to the Blender source code.
Regards, Harley Acheson
Virtual Dogsbody
Info Tech Department
Shawnigan Lake School
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