Archived posting to the Leica Users Group, 1999/07/27

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Subject: Re: [Leica] another dumb question
From: omegaman <>
Date: Tue, 27 Jul 1999 14:26:36 -0700

Alex Brattell wrote:
> >perhaps a dumb question, but I keep running into "A4" size prints, etc, =
> >etc.  What are the "inch" equivalents to these "A-series" size prints?  =
> >Can someone clarify this?  Are these standard "European" size prints, =
> >and if so, does the "A" stand for anything??  Thanks, Kent
> Can't answer this - but I have an equally stupid question that I can't find
> the answer for;
> What does the 'f' in f-stop stand for?
> (I've asked people and looked in books, and had to admit to the person who
> asked me - haven't got a clue!)
> thanks
> alex
> ____________________________________________
> ___________________________________________
The "f" in f-stop stands for focal length.  If you have a 50mm lens and
have it set at f/8, then the product of 50/8 (50 divided by 8) is the
size of the opening made by the iris.  In this example the lens opening
at f/8 is 6.25mm.  100mm at f/16 has also a 6.25mm opening.
Randolph Carlisle