Re: [APML] 7331 (again!)

[ZenAstro <zenastro@home.com>]

>
>I have been working on an article on "noise" in scanned photographic
>images for my club's newsletter.  I have been looking at the problem
>with the tools I have available -- a camera, a couple of films, and a
>scanner.  One could easily argue that these tools are inadequate for the
>task, however, these are the only tools I and most APML subscribers have
>at our disposal.  I have been using the concepts of spatial random
>fields (SRF) to quantify noise in scans from a color (PJ400) and a black
>and white (tech pan) film.  I have also looked at how averaging images
>and smoothing images alters statistical measures of image noise.
>
>As you would expect, the variogram sills for the scanned tech pan images
>are much lower than the variogram sills from the PJ400 images.
>Surprisingly, the variogram ranges are very similar for the two films.
>Averaging images affects the variograms in the manner predicted by
>theory (i.e., a reduction in the variogram sills, but no change in the
>variogram ranges).  Smoothing images also change the variograms in the
>expected manner (i.e., a reduction in the variograms sills, but an
>increase in the variogram ranges).  The ideal method for reducing
>"noise" as measured with variograms would reduce the sill and the
>range.  With your background in image science, could you recommend a
>procedure that would accomplish this?


Hi Joe,

What is a variogram, and what is a sill, and a range. How do they measure 
noise?

Thanks



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