[Bf-committers] Blender Film Plane

[Roger Wickes]

Fantastic first project! Great research, understanding,
and solution. Good job Harley!

 --Roger





________________________________
From: Harley Acheson <hacheson at shawnigan.ca>
To: bf-blender developers <bf-committers at blender.org>
Sent: Sat, May 15, 2010 1:03:28 AM
Subject: [Bf-committers] Blender Film Plane

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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