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aperature number vs f number

Started 10 months ago | Questions thread
Toronto Photography
OP Toronto Photography Senior Member • Posts: 1,064
Re: aperature number vs f number

Lemming51 wrote:

Toronto Photography wrote:

F stops I get.

at f13 I have an apeture number of 7.3

Is it the same thing but a different scale or is it different.

What is the scale if the same thing? (like say Kelvin and Celsius?)

The "aperture number" of 7.3 is the number of stops smaller f/13 is compared to f/1.0

SquareRoot(2) ^ "aperture number" = f/# ("^" means raised to power or exponent)

Sqrt(2)^1 = f/1.4

Sqrt(2)^2 = f/2.0

...

Sqrt(2)^7.333 = f/13 (12.7)

Sqrt(2)^7.667 = f/14 (14.2)

Sqrt(2)^8 = f/16

Ok what is the "Aperture number" actually called and what is it used for?

 Toronto Photography's gear list:Toronto Photography's gear list
Canon EF 70-300mm f/4-5.6 IS USM Canon EF-S 55-250mm f/4-5.6 IS II Canon EF 24-105mm F3.5-5.6 IS STM
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