theMusicMan

23rd July 2010, 04:04 PM

Hi All

I was asked a question the other evening that I was not able to answer, and the question was; "what exactly does fn.n mean"?

Now of course, I was able to explain what aperture is, it's relationship with exposure, DoF and shutter speed etc, but I have no idea how the actual value for a given lens is actually calculated.

What is the mathematical formulae for calculating the aperture of a given lens? Is is something like the ratio of physical aperture size to distance from sensor or something like that?

Can some tekno person help me here please...?

Thanks.

I was asked a question the other evening that I was not able to answer, and the question was; "what exactly does fn.n mean"?

Now of course, I was able to explain what aperture is, it's relationship with exposure, DoF and shutter speed etc, but I have no idea how the actual value for a given lens is actually calculated.

What is the mathematical formulae for calculating the aperture of a given lens? Is is something like the ratio of physical aperture size to distance from sensor or something like that?

Can some tekno person help me here please...?

Thanks.