Re: 18% grey
Re: 18% grey
- Subject: Re: 18% grey
- From: Roger Breton <email@hidden>
- Date: Sat, 09 Apr 2005 12:16:00 -0400
I always set step 9 on my reflective IT8 targets to RGB 127/128 as per Bruce
Lindbloom original instructions in ColorSynergy v4.x User Guide, because I
understand that step 9 corresponds to an aim value of L* = 50. But I must
confess I never studied the mapping between RGB 127/128 to its corresponding
gamma, in the scanner profile. Why? Because it never struck me intuitively
as being important.
But now, in the context of this thread, I'll have to revisit these ideas.
Not that I particularely care about scanner gammas -- I think it's lost,
conceptually in the construction of a LUT-based scanner profile, unless one
creates matrix-shaper scanner profile -- but I'm curious as to its effect on
mapping tones onto a given RGB working space and the goal of preserving or
enhancing contrast.
Thank's for your help.
> I can't speak for all profiling apps, however, if the scanner gradation
> is first set up for 128's in the .72 density range, (which is nearly
> equal to step 9 on most IT8 7.1 targets), and if basICColor scan+ is
> used to build the input profile with "keep gray balance" selected, then
> the native contrast and saturation of the original chrome is maintained
> into the rgb scan using this method.
>
> - Jon
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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