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ISO on the R5

Started 10 months ago | Discussions thread
John Sheehy Forum Pro • Posts: 26,688
Re: I see!

MarshallG wrote:

Well… my eyes tend to defocus and glaze over on the math, but mostly because a 50,000 foot view of the data shows a basically flat line, nothing spiky.

It's nice to see the data, and a nearly-straight-line based on standard deviations may prove a limited difference, but standard deviations have nothing directly to do with visible noise. It is a hollow currency which depends on the noise character being the same always (usually assumed to be 1/f), only varying in intensity.

Imagine that you are laying under a glass table, looking up. Somebody comes along with bottles of black, white and grey sand. They poor the sand into little piles, one at a time so that there are clusters of black or gray or white, with dozens of each clumped together. You clearly see the "noise" of these B&W grains. Then, they take their fingers and keep mixing all the sand together, until it all looks grey to you. What happened to the standard deviation of the sand? Nothing. What happened to the histogram of the sand? Nothing. Yet, as far as you can see the noise is mostly gone after it is all randomly mixed. This is a removal of spatial correlation.

Standard deviations do not describe noise in a spectrum, which is where we SEE noise.

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Beware of correct answers to wrong questions.
John
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