How to assess the quality of an emulation? or a profile?
How to assess the quality of an emulation? or a profile?
- Subject: How to assess the quality of an emulation? or a profile?
- From: Randy Norian <email@hidden>
- Date: Thu, 24 Jun 2004 10:00:19 -0500
This is a typical application, but I'm simply trying to understand it a
little better.
I have 2 devices-
1) a Polaroid Polaproofer, which is dialed in nicely- makes good
neutrals when fed SWOP neutral builds, etc. The shop is very happy
with the output.
2) an HP5000 inkjet, which is being used to make cheap proofs in lieu
of of Polaproofs.
Linearize the inkjet and set ink reduction, then profile both with
Spectroscan and Gretag profilemaker 4.1, load the profiles, Voila,
output from inkjet is a good match, close enough to send to the
pressroom. I have to say it was almost too easy.
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.
a) visual of course
b) numerical?
1) I printed the IT8 target off the Polaroid, read the values.
2) print IT8 off the HP5000, *while it is doing a Polaproof emulation*
and read values. also created a profile of this "workflow" which I
called 'HP doing Pola emulation.icm"
compare raw data using Profilemaker's Measure tool- Compare
the average delta-E btwn the 2 sets of data is 3.95
best 90% is 3.57
worst 10% is 7.41
Visually, the proof off the inkjet is very acceptable except that the
neutrals are casted a bit green, but no matter.
-----------------------------------
Next, I look at the 2D gamut of the resulting profiles.
Raw inkjet= large and all-encompassing
Polaroid = almost exact mimic for US Sheetfed- as it is intended to be
"HP emulating Polaproof.icm" has reduced itself to an almost exact
match for the Polaproof gamut. Bingo!
----------------------------------
Last, I look at the 3D gamut distribution of all 3 profiles.
The Pola is arrow-straight, both primaries and secondaries.
The raw Inkjet looks like a mad octopus, curving all over
The "Inkjet doing Pola emulation" is again a very good match for the
Polaproofer, both primary and secondaries, and keeping space between
the dots all the way to the ends of the 'arms' . I could not really
have asked for much more.
---------------------------------
Are these valid ways to assess the emulation? Are there additional
techniques that I can use? I ask because I have a few 'problem child'
applications ( other printers, proofers) where I am not getting as good
an emulation, and am trying to assess whether my profiles could be
better, or the RIP is not doing as good of a job, or what.
What I'm evaluating here is the combination of 2 profiles AND the
Wasatch SoftRip software. Now, how do I break it down so I can assess
the quality of just one profile? or just the RIP?
I will post that question separately--- this is getting kind of long-
Randy N.
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