Is there a formula for converting say a 70-210 lens to what it would mean in zoom such as 10x or 12x?
Comparing lense
Posted: April 6, 2008 - 7:23pm
Re: Comparing lense
Posted: April 7, 2008 - 1:29am
Not sure you're asking the right question. 10x zoom means that the telephoto end is ten times the wide end. So a 10x zoom starting at 70mm would end up at 700mm, and isn't practical.
You may mean converting the focal length to a smaller sensor.
Re: Comparing lense
Posted: April 8, 2008 - 12:09am
Quote:
Is there a formula for converting say a 70-210 lens to what it would mean in zoom such as 10x or 12x?
The way I read it, this would be a 3x zoom, i.e. 210/70=3 (with a 70mm "wide" end) 
Re: Comparing lense
Posted: May 7, 2008 - 2:38pm
With a 35mm film camera a 50mm lens is considered 'normal'.
So just divide by 50: 500mm/50 = 10X . With a digital you
would have to include the crop factor:
(500x1.5)/(50x1.5) = 750/75 = 10X.
70/50 - 210/50 = 1.4X - 4.2X zoom.
/Clay
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