And that's because, although light falls off with the square of the distance,
so does the apparent size of the object from which it's being reflected,
resulting in the light and the size of the area it covers remaining
proportional. Otherwise, exposure would change with distance. You can go
outside and peek through the window at your television screen and, yes, it
won't be any dimmer, but it'll sure look smaller. I took my flying squirrel
photos with a slaved flash 3 feet from them, but the camera was 25 feet away.
The correct exposure would've been the same if the camera has been right by the
flash; the critters would've just looked bigger.
Walt
--
"Anything more than 500 yards from
the car just isn't photogenic." --
Edward Weston
-------------- Original message ----------------------
From: AG Schnozz <agschnozz@xxxxxxxxx>
>
> When you are working in a studio environment, the
> exposure(brightness) of the subject is determined by the
> flash-to-subject distance (and power output). Provided you are
> using the exact same F-stop, the exposure to the camera is
> exactly the same regardless of how far or near the camera is to
> the subject AND what focal length the camera lens is. It's like
> the sunny-16 rule--it works regardless of the lens or
> subject-camera distance.
>
> A viewfinder's optics are exactly like the camera lens in the
> above example and the focus screen is a "backlit object" which
> the lens is focused on. Our eyes are essentially the "film" in
> this example. Changing magnification (apparant optical size of
> the focus screen) is a matter of changing the optics of the
> viewfinder's eyepiece. Remember, the actual surface area of the
> focus screen does not change in any way--therefore it's actual
> brightness is fixed.
>
> A television or computer screen is just as bright if you are
> inches away from it or sitting across the room from it. If you
> sit across the room and use binocs to view the screen it's the
> same as if you were sitting right in front of the screen.
>
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