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RE: [APML] Wondering about histograms
Hi Alan
>> First of all, could you tell us how do you scan your images? 12bits
>> RAW?
>Yes, and saved as a tiff.
Ok. So, don't worry too much about the wide of the histogram. You have all the info that your scanner is capable of adquiring.
>> BTW, it is a very good idea to do multiple scans of your data, and
>> then average them, or median combine. You'll have to register the
>> images, of course.
>How is this done? Do you mean taking several single scans and combine
>them? It seems that I've heard tell of folks who do this with their
>scan software at the time of the original scan. It may be that I've
>mis-understood though.
There are "two types" of multiple scans. There are some softwares that makes that automatically, I think that it was for some Nikon or Minolta scanners. Basically, it scans each frame several times and combines the shots in any way.
With your SS400 what you have to do is just scan your images a lot of times... say 4 or 8 times. Becouse the film holder isn't always located at the same position, and the result will not be the same, you'll have to register (align) each frame to a reference one (for example your first scan). You may use RegiStar or other software for that, but I think that it would be quite good to try just translations (x,y shifts).
Multiple scans will reduce the noise introduced by the scanner and you'll end with a smoother histogram.
Oh, by the way... noise introduces an effect of widening the gaussian like zone of the histograms. So, if you have two images, that just have different amounts of noise, you'll see a narrower one with the less noisy. Try this with the histogram of a image after and before noise reduction techniques.
And another btw: vignetting/uneven field illumination also contributes to this effect!
Regards,
Carlos Milovic F.
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