Silverfasts gamma 1.8/2.0/2.2

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redrebel
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Silverfasts gamma 1.8/2.0/2.2

Postby redrebel » Thu Mar 09, 2006 9:11 pm

When scanning negatives under windows using colour profile "Adobe1998" or "sRGB IEC 61966-2.1"....which gamma setting should I use? I mean the setting "Option -> General -> Gamma gradation".


It's default is 2.0 for negatives I think, but the manuals say you should use 2.2 for RGB / SRGB and 1.8 for Apple RGB...

What is true, and more importand can this cause a difference between the scan preview and the final output in Photoshop CS2 ?

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RAG
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Postby RAG » Fri Mar 10, 2006 1:16 am

Quote from "SilverFast the Official Guide" pp61

"Gamma-Gradation Changes in this value affect the midtone brightness of the image. Most desktop scanners will work best with a value of 1.8, but if you feel that all of your scans tend to be too dark, increase the number to brighten the image. Conversely, lowering the number will darken the image (the minimum gamma value is 1.0, but you should never reduce it to that extent)."
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redrebel
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Postby redrebel » Fri Mar 10, 2006 10:27 pm

Yep your right but in the "Colour Management Tutorial" on page 37 the gamma 2.2 setting is linked to Adobe RGB and sRGB.

I thougt that the gamma setting only influenced the output and not the preview. But I discoverrd that the older version of silverfast 6.4.3r8 doesn't alway update the preview , while the newer version 6.4.3r9 always forces a preview update (rescan) when changing settings.


But still the output in Photoshop is a bit warmer then the preview is in Silverfast...

BB
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Postby BB » Mon Mar 20, 2006 9:42 am

As far as I understand, the gamma gradation corresponds to the scanner's gamma, i.e. the way the scanner's sensors interpret brightness values. This has nothing to do with the other links in the color management chain (like PhotoShop).
There was a good article on that on Ian Lyons' site:
http://www.computer-darkroom.com/gamma/gamma_1.htm

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