Your verbal explaination is great, Mark. But there is a bit of a problem with your math. Simply put f-stop is a light transmission factor, not and not the same thing as aperture size. I know I played with that same formula for a long time, and it did not work until I realized that. Change f (f-stop) to a (aperture diameter) and it works fine.
I'd be interested in playing around with aperture diameter in the equations to see how it works.
How do you determine the aperture diameter (short of dismantling your lenses and measuring)? F-stop is focal length divided by the diameter of the front of the lens. I've seen lenses where the aperture is directly behind the front element, and for those you could just divide the focal length by the f stop an have the aperture diameter. But with the aperture located in the rear of the lens it is smaller than the front element in any case - so how do you determine it's size?
- MCC
- - - - - - - - - -
Mark Cassino
Kalamazoo, MI
[EMAIL PROTECTED]
- - - - - - - - - -
Photos:
http://www.markcassino.com
- - - - - - - - - -
