Re: Projection and focus sharpness

[fj834@xxxxxxxxxxxxxxxxxxxxx (Dr. George A. Themelis)]

>My brother-in-law and I were discussing what projection lens might
>be best if you didn't want a warped slide to be too far out of focus.

Is that how you guys spent your vacation time?  ;) ;) ;)

>so I did the math.  There were pages of derivation using Gaussian
>and Newtonian forms of the lens equation which I'll spare you. 

I guess I should feel guilty for eating and sleeping for 4 days...

>So for a given screen size, if F is in the normal range of 90 to 150 mm,
>and the f/number is held constant, there is no real change in the diameter,
>C, with focal length.

Why didn't TDC make the 4" lens as standard and have an option of even
shorter FL?  Same question for VM.  Images from the Stereomatic projector
are too small to be enjoyed in a normal size screen from normal to long
projection distances...  Are shorter projection lenses more expensive to
make?

George


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