f-number equivalent between m43 and FF

Started Mar 25, 2014 | Discussions thread
Detail Man
Detail Man Forum Pro • Posts: 16,682
Re: SNAP ! Where it is ?

Jack Hogan wrote:

crames wrote:

Another way to look at it is in the frequency domain .

I wonder if that's not a misleading graph in this context, as I think it applies just to read noise: it shows the amplitude of the signal decreasing with increasing frequency, but the noise being constant with it. I understand this discussion to be mainly about rms shot noise, which I think would also decrease with a decreasing signal.

Your point makes sense to me, Jack - as while noise is spectrally "white", photon shot noise itself (as opposed to readout noise) is (also) scaling with the number of transduced photons.

ejmartin's post on that thread:

http://www.dpreview.com/forums/post/3985100

... references this web-page:

http://steveharoz.com/research/natural

... which states:

Plots of the power spectra from the natural images are shown above. These plots have nearly straight lines with slopes of approximately -2, which corresponds to an f^(-2) trend.

... and:

These plots have been observed for tens of thousands of images, and the f ^(-2) trend consistently differentiates natural images.

... but does not differentiate between noise sources varying with signal level and those that do not.

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