Equivalent focal length for MFT lenses

Started Apr 12, 2013 | Discussions thread
JeanPierre Martel
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Re: Equivalent focal length for MFT lenses
In reply to KenBalbari, Apr 13, 2013

KenBalbari wrote:

The f-number does NOT tell you anything about the density of light or number of photons.  That is going to depend as well on the scene luminance and exposure time.

Please Ken, let's not complicate the discussion. We are talking about the same scene, shot in the same lightning conditions and same ISO setting but taken by two cameras -- m4/3 camera and a Full-frame.

What I'm saying is that the diameter of the opening of the iris will be different in a 600mm vs 12mm lens but the ratio of that opening vs the focal length will be the same when both are set at F/2,8 and when, of course, they are both m4/3 lenses.

Because the F stop number is a ratio and nothing but a ratio. It's not an absolute measurement in mm, for example.

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