BetterPhoto Q&A
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Photography Question 

Archana Padhye
 

What is teh significance of 1 in the lens aperture


On any lens the maximum aperture is indicated in the form of a ratio like 1:5.6. Can anyone tell me the meaning/importance/significance of '1' in the ratio? Since ratio is the comparison, here which apertures are being compared?


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April 20, 2004

 

Bob Cammarata
  The aperture numbers represent a fractional equivalent of the lens focal length, and determine the size of the opening...(in millimeters). The "1" refers to the lens focal length.

Example....: On a 200 mm lens at f-4, the aperture opening would be 50 mm wide,...(or 1/4 of the focal length).
1/4 of 200 is represented as 1:4.

Make sense?


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April 20, 2004

 
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