Re: Profile Inspector & grid points
Re: Profile Inspector & grid points
- Subject: Re: Profile Inspector & grid points
- From: Steve Upton <email@hidden>
- Date: Mon, 27 Aug 2001 11:02:12 -0700
At 12:50 PM -0400 8/27/01, Vanderlinden, Thomas M. wrote:
good morning - - - - -
My curiosity was raised by Bruce J. Lindbloom's reference
to "Apple's ColorSync Profile Inspector".
I have not been able to find reference to it at www.apple.com.
it is a little tough to find as it is part of the ColorSync SDK. If
you go to www.apple.com/developer then follow the links to
documentation for ColorSync you should be able to find it.
I was about to ask for help in finding it, and then wondered
if we're actually talking about the CHROMiX ColorThink
component that is called Profile Inspector,
No, although I did choose to name it similarly I was hoping the
ColorSync Profile Inspector was obscure enough to avoid confusion in
most cases.
which had this to say about the B2A1 tag in a profile
created for a color laser printer using the GretagMacBeth i-1:
Double Precision(16 bit) Multi-Function Lookup Table
3 input channels, 4 output channels
25 CLUT grid points
A profile of the same printer, created using Praxisoft WIZIWYG
had the following in the B2A1 tag:
Single Precision(8 bit) Multi-Function Lookup Table
3 input channels, 4 output channels
32 CLUT grid points
So, does "x CLUT grid points" mean the same thing as
"x grid points in each dimension"?
yes it does. I just tried to put a more human-friendly face on it.
And aside from being odd or even,
are more "grid points" a good thing?
Generally I would agree. This is analogous to the number of color
patches used when generating the profiles in the first place. If the
device is well behaved (from a linearity point of view) then less
patches and less grid points are typically fine as the interpolation
required when rendering or proofing color will get very close. If it
behaves strangely in some areas of the color space, then more patches
and more grid points are a good idea.
As the very knowledgeable Mr. Lindbloom mentioned, odd numbers are a
wise thing for Lab->Device tables as the range of a* and b* vary from
the negative, through zero and on out to positive values. Without an
odd number of points on the grid, any neutral values (where a* and b*
are 0) would have to be interpolated (read estimated) and that is not
a good idea. Neutrals seem to be a point of concentration and
contention for many people so we want them nailed down!
Regards,
Steve Upton
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