Re: How to assess the quality of an emulation? or a profile?
Re: How to assess the quality of an emulation? or a profile?
- Subject: Re: How to assess the quality of an emulation? or a profile?
- From: Roger Breton <email@hidden>
- Date: Fri, 25 Jun 2004 09:48:57 -0400
>
Now, how do I put a number on the quality of this emulation? What
>
method do you guys use? I want to do this because of course I'm
>
interested in making the match even better in the future. I also wish
>
to do emulations using other proofers/ printers and want to be able to
>
rate how well this is working.
You have two parts to test in an output profile, the device (CMYK in your
case) to Lab part and the Lab to device part. You want to test those
independently. The first part, called the A2bx direction by the ICC, is
easy. Just open up the characterization target in Photoshop, assign your
printer target to it, make sure you have AbsCol turned on in
ConversionOptions, and systematically compare the original measured data to
what Photoshop tells you the patches measure in Lab with the color picker.
Just move the picker over the individual patches while keeping an eye on the
Info palette. The second part, the B2Ax direction, is less straightforward
to test. One way is to design your own Lab target in Photoshop. Convert it
to your printer profile, in AbsCol, print it and measure it. Compare the
resulting measured Lab values returned by your instrument with what you know
were the starting Lab values. Calculate DeltaEs. Hopefully, you should not
be too far. But that depends on where the starting Lab values were relative
to the printer gamut. If you start off a lot of out-of-gamut colors, the
DeltaEs will be high.
Roger Breton | Laval, Canada | email@hidden
http://pages.infinit.net/graxx
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