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Re: [OM] f/0.x lenses

Subject: Re: [OM] f/0.x lenses
From: Jan Steinman <Jan@xxxxxxxxxxxxxx>
Date: Fri, 12 May 2000 09:06:21 -0700
I always understood the f number to refer to the ratio of the actual
scenery light intensity appearing inside a lens.  Ex: f2 would let in
1/2 the light intensity.  Ergo, wouldn't f < 1 imply that light
amplification was taking place.

Not quite. "f" is the ratio of focal width to focal length, and depending on the lens, may have little to do with the actual light coming through.

When you adjust the diaphragm, for example, you are changing the focal width, and thus the ratio.

So a 50mm f0.5 lens, for example, would have a 100mm focal width.

: Jan Steinman <mailto:Jan@xxxxxxxxxxxxxx>
: Bytesmiths <http://www.bytesmiths.com>

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