Mainly uncollimated (non-laser) light spreads out the further away from a
hole. The amount of light varies directly according to the hole size and
indirectly according to the distance from the hole to the film.
tOM
On Tuesday, August 13, 2002 at 14:30, Daniel J. Mitchell
<olympus@xxxxxxxxxxxxxxx>
wrote re "RE: [OM] Magnification factors" saying:
> > > Effective f# = (m+1)*(marked f#), where m is magnification
> > > In stops, it's log((m+1)**2)/log(2)
> >
> > Yes. Rearranging the 1st equation, you get.
> >
> > marked f# = (Effective f#) / (m+1)
> >
> > The effective f# is what the film will experience.
> > The marked f# is the lens marking.
>
> Just curious -- where does this come from? Is it based on light loss
> bouncing around inside the extension tubes, or less light on the film
> because the subject area is smaller, or something else entirely?
>
> -- dan
>
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>
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