Subject: Re: Focus Target
From: Andrew Hofman <[email-masked]>
To: [email-masked]
Date: Wed, 31 Jan 1996 14:39:21 -0800

>Andy, you need to look in the CAMERA PANEL.  Lens focal length, in millimeters,
>is there, and user editable via ZOOM FACTOR.

I agree, focal length is there. But they call it "Equivalent Lens", and have
used the more common "Focal Distance" for something completely different --
Focusing Distance. A slight difference in words, but a big difference in
meaning. 

>FOCAL DISTANCE is an entirely
>different setting, affecting rendered output only.

I haven't tested that with Lightwave, but in the real world, focal length
and F-stop both directly affect focusing distance and its resultant depth of
field.

>On a different note, in the current release, the FOV numbers returned look
>inaccurate.  Comparing the numbers in lightwave with corresponding values
>in the lens tables found in the Cinematographers handbook show that the
>aspect ratio of your FOV should match the aspect ratio of your aperture and
>your image, and they don't.  
>

Not only that, but the "Equivalent Lens" settings don't match what are
considered normal or baseline settings for different image formats. For
example, Lightwave has a 24mm Equivalent Lens for 35mm film. Everywhere
else, I have seen this as being 50mm. Of course, it's easy enough to get a
50mm lens by using a Zoom Factor of 2.0833. But . . . ?

Andy Hofman
LumaQuest Productions           
Animation and Dual Raptor 3 Rendering  
[email-masked]
513-643-7333