location of code correlating FOV and "Lens" settin

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macouno
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Joined: Tue Nov 18, 2003 3:37 am

Post by macouno »

Sure, blenderartists is fine... you can find my address though www.macouno.com if you want to just send me something.

Also perhaps nice for you to consider irc chat. There are a bunch of blender related channels also with coders, that can really help get things going.

goodguy20k
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Joined: Fri Aug 31, 2007 6:45 pm

Post by goodguy20k »

Probably trying to keep people from pestering the coders privately. ;)

I'm listening. I'm also over on blenderartists, same username. I'll be interested to see what you've got! :)

chipmasque
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Joined: Mon Aug 20, 2007 6:31 pm

Post by chipmasque »

macouno, I sent you an email with an attached text file.

goodguy20k, you should have a PM in your blenderartists mailbox.

Thanks both for your interest!

itsjimbo_dontyouknow
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Joined: Wed Jun 10, 2009 4:50 pm

The origin of 16

Post by itsjimbo_dontyouknow »

Hi guys

I know this is an old thread but I suppose someone might need the full story.

The origin of 16 is to do with the focal length. Blender assumes a camera with an aperture 1/16 of the focal length. this is equivalent to an F-number of 16 hence 16f.

What the lens value in blender represents is the image size for an F/16 lens. The FOV arrises from the chief ray angle from the edge of the image, that is the ray that passes straight through the centre of the aperture.

Interestingly it's handled inversely. The square that represents the fron of the camera is a constant area. as you increase the 'Lens' number you increase the length of the camera object. If you imagine the square at the front being a projection of the image size from the lens (the point where diagonals meet at back). This would be equivalent to having it behind the lens [as you would expect] (so it looks backwards) and so as you increase the Lens Number the image gets further from the lens so the field of view decreases.

I have to stress, 16 is an arbitrary number, it's the number I think that iso standards are calculated from. In the case of blender it is simply a scaling factor that in my opinion, they should have left out.

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