Originally Posted by
Doremus Scudder
Well, no again.
Magnification functions independently of format as well. Getting 1:1 on 4x5 requires 2x the extension needed for focusing at infinity and the amount of light hitting the film is reduced by two stops or a factor of 4 (according to the inverse square law). The resulting image is "life size," hence a 4x5" object would fill the frame.
Getting 1:1 on a 35mm camera is exactly the same. It requires twice the extension needed for infinity, the amount of light reduction is exactly the same (inverse square law again) but this time, a 24x36mm object will fill the frame.
Yes, effective aperture depends on magnification, but it, too, is format independent.
Filling a frame of 35mm film with a 4x5" object is not 1:1, it's a different magnification ratio, hence the different exposure required. While "creating the equivalent image" on a smaller format will, indeed, require less magnification and, hence, a smaller drop in brightness, you're not comparing apples to apples here. Still, I get your point. That's why I suggested to the OP to maybe use a smaller format in the first place.
Best,
Doremus
P.S: Sorry I made you *sigh*.
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