Re: 116 vs. 716 (part II)

[P3D Eric Goldstein <egoldste@xxxxxx>]

P3D Dr. George A. Themelis wrote:
> 
> Regarding lenses, image size and brightness:
(snip)
> How about brightness?  Well, image brightness is inversely proportional to
> image size.  FL of lenses has nothing to do with brightness.

True enough, but different lenses often have different *speeds*. I have
seen 50s stereo projectors with f/2.2, f/2.8, and f/3.5 lenses. These
aperture differences do make a noticable difference in screen brightness
(a question posed in your part III), easily as much as switching between
500 and 750 watt lamps...

George, do you know if TDC 4" and 5" lenses are of the same speed?


Eric G.


------------------------------