I said in my previous email. f=focal length. On Mon, Oct 31, 2011 at 8:02 AM, Collin Brendemuehl <[email protected]> wrote: >>It also makes the notation of aperture = f/x much more meaningful. >> >>f is your focal length and x is your diameter fraction. >> >>It's why you see apertures listed as f/2 or f/64 and etc. It's >>appropriated from a formula. > > > In addition, what does that letter "f" stand for anyway? > It is a "function". > This formula/function allows you to use two different focal length > lenses and obtain the same exposure. It resolves the problem of > differing aperture sizes and lens focal lengths.. > > >>On Sun, Oct 30, 2011 at 8:08 PM, John Francis <[email protected]> wrote: >>> On Sun, Oct 30, 2011 at 03:55:21PM -0400, Mark C wrote: >>>> > >>>> Thanks - I just checked Wikipedia and got the equation for the area >>>> of an f-stop: Area = PI x (focal length / f-stop)^2. Comparing 50mm >>>> and 100mm confirms that the size of a 100mm f-stop is the same as >>>> the f-stop two stops lower in number on a 50mm. >>> >>> That's doing it the hard way ... >>> >>> You don't need to calculate area, square any values, etc. >>> >>> F-stop is simply the ratio between aperture diameter and focal length. >>> So the same plate (with, by definition, the same diameter aperture) >>> will have f-stops that differ by a factor of X (two, in your case) when >>> used with lenses that have focal lengths that differ by a factor of X. > > Sincerely, > > Collin Brendemuehl > "He is no fool who gives what he cannot keep to gain what he cannot lose" > -- Jim Elliott > > > > > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. >
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