Hi Jan,
Also, different lenses transmit different percentages of light. The
most obvious example of this is mirror lenses because of the
obstruction, and zooms, with all their glass/air surfaces.
In the movie biz, they being very sensitive to light changes within a
scene, and between scenes and lenses, use a "true stop" or "t/stop"
which is photometrically accurate.
BTW, I have used an f/0.95 lens. On a movie camera.
Tom
At 2000 May 12 - Friday 9:06, Jan Steinman <olympus@xxxxxxxxxxxxxxx>
spoke about *Re: [OM] f/0.x lenses...* saying
> >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.
-------------------------
Tom Trottier, Abacurial IT Consulting ICQ: 57647974
400 Slater St. Suite 415, Ottawa Ontario Canada K1R 7S7
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