Re: Newsprint G7 calibration
Re: Newsprint G7 calibration
- Subject: Re: Newsprint G7 calibration
- From: Steve Upton <email@hidden>
- Date: Sat, 24 Mar 2007 19:09:22 -0700
At 11:16 AM -0400 3/24/07, Roger Breton wrote:
>I did use the latest of everything. Believe me. Freshly downloaded off
>Gracol's site. And, I always export as CGATS out of ColorPort.
The concern I had was about a ranging choice in CGATS. So in regards to IDEALink, the range chosen may affect the results.
> I, too,
>realize the spectral data is useless for IDL as we know that all
>"densities" reported are derived out of XYZ and not StatusT, and those
>"densities" don't even enter into the G7 calculations anyway.
Yes they do, or at least they could. The calculations can be done with XYZ or density values if desired.
>BTW, what good
>is it to have "densities" displayed in the interface when they don't follow
>long time established industry conventions like ANSI and ISO StatusT? Might
>as well not display the information at all, it does more harm than good,
>IMO.
Which density would you choose that would be the same around the world?
Which instrument would you base it on? Density values between X-Rite and GretagMacbeth instruments vary a lot. Colorimetry varies less between instruments as far as I have been able to determine.
Density based on XYZ is always the same. It is also gaining favor in the standards groups.
Ultimately measurements like TVI are based on relative calculations anyway so the numbers usually come out fairly close.
>
>Anyhow, for this test, everything was plated as is. Meaning, the 50% dots in
>the P2P23xn TIFF file ended up as reading 50% on the plate with the plate
>dot meter. Nothing else I can do. Except, I noticed, that dot percentages
>below 50% were increasingly lower than linear and dot percentages above 50%
>became increasingly higher than linear.
And that should be fine.
>BUT WE ARE TOLD IN THE "G7 How To"
>that the plates don't have to be linear to begin with. So I did not bother.
>I suspect this could have something to do with the strangeness of my
>results.
It shouldn't.
What would be great is if you could send me your data files offline. Then I can take a look at see what might be causing the issue you are dealing with.
Regards,
Steve
________________________________________________________________________
o Steve Upton CHROMiX www.chromix.com
o (hueman) 866.CHROMiX
o email@hidden 206.985.6837
o ColorGear ColorThink ColorValet ColorSmarts ProfileCentral
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