Well, not the best analogy I've ever come up with. The bottom line is, equal
f/stops, no matter the format, come out the same in the end. If that were not
so, then a scene you might shoot with a 35mm camera at 125th sec. at f/8, I
would have to shoot at some different exposure with the RB-67. That's not how
it works. The 50mm f/3.5 Zuiko wide open admits light through a hole about 14mm
in diameter, while the 127mm f/3.8 Sekor is pouring light through a hole a
little over 34mm in diameter, which is probably admitting three or four times
as much light as the Zuiko. (I'll leave it to somebody smarter tham me to do
the pie are square calculations.) But, and this is what I was trying to explain
before, the light coming through the bigger hole has to light up a
proportionately bigger viewfinder AND, subsequently, expose a similarly larger
piece of film. So, it's all the same in the end, 'cause f-stops is f-stops,
for all practical purposes.
I need more coffee to explain this any more better. :-[
Walt
--
"Anything more than 500 yards from
the car just isn't photogenic." --
Edward Weston
-------------- Original message ----------------------
From: hiwayman@xxxxxxx (Walt Wayman)
> Remember, light falls off with the square of the distance. For instance, if I
> take a photograph of, say, the cat lying by my feet from a distance of four
> feet, then I move back and take another shot from eight feet, only half as
> much
> light reaches the camera and comes out through the viewfinder at eight feet
> as
> did at four. But the cat looks exactly the same, because the image is only
> half
> as big, so half as much light spread over half as much area looks, and
> measures,
> the same. Obviously the converse would be true: twice as much light spread
> over
> twice the area would be the same intensity.
>
> If a larger viewing surface could cause the image to be brighter, then an
> 8x10
> view camera's ground glass should look like a plasma TV screen. It don't, as
> anybody who's sweated and muttered profanities under a focusing cloth can
> attest.
>
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