At 7:58 PM +0000 2/14/02, olympus-digest wrote:
>Date: Thu, 14 Feb 2002 07:53:48 -0800
>From: "Dave Dougherty" <davdou@xxxxxxxxxx>
>Subject: [OM] Re: Flash Tutorial
>
>I well remember shooting in the Field House at the University of Wyoming in
>1963. I had a Honeywell Flash mounted on a Mamiya C-3 TLR and wanted to
>shoot a choral group of some size. I placed a remote slave flash about 12
>feet from the group and stepped back to about 35 feet to frame the shot.
>
>The head of the Photography for the Athletic Department and now an exec with
>the Wyoming Travel Commission sniffed that I was wasting my time and film as
>the combination wouldn't work. I took the shots.
>
>The choral group was well lighted and the shot worked great. Ken was right
>on that the location of the flash not the camera is the arbitor of the final
>exposure.
Yes, it's a basic property of imaging optics. The brightness of the image on
the film is proportional to the brightness of the imaged object, regardless of
the distance from lens to object. As the object moves away from the lens, less
light from the object falls on the lens, but the resulting image is smaller,
and the effects exactly cancel. The f/stop controls the proportionality
factor. The full equation may be found in textbooks on optics, and some
textbooks on photography.
The brightness of the object was set by the power of the flash and its distance
to the object; the distance to the camera is irrelevant, just as you have
observed.
Joe Gwinn
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