RE: Posterization in a Press Profile?
RE: Posterization in a Press Profile?
- Subject: RE: Posterization in a Press Profile?
- From: Roger <email@hidden>
- Date: Fri, 25 Sep 2009 18:10:07 -0400
Brian,
The reason you're seeing posterization is because of the sampling scheme
used to collect the data fro the press. The patches were laid out for
measuring with the EyeOnePro, in strips. It is fine for reading with the
ruler but, when the patches are rearranged in the standard visual layout, in
MeasureTool or PatchTool, huge tonal breaks become visible. The fix for this
problem is to either go back to pres with a different target or use
mathematical smoothing (third-order polynomial). I don't know MeasureTool
has that capability? Nor ColorPort, nor Argyll (not that I know of?).
Without smoothing, I'm afraid this profile will remain of limited value.
/ Roger
> Hello all-
>
> I'm trying to troubleshoot what I think is odd behavior on the part of
> a profile I measured from a press. I've been hearing from some of our
> designers that they are seeing some posterization in their images when
> they use this new profile. I've posted some of my test examples here:
>
> http://brainpilot.com/press_profile/profile_testing.html
>
> As you can see from the four images, when I take Bill Atkinson's LAB
> test image and a Granger rainbow and convert them to this press
> profile, there is a significant amount of posterization in the result.
> The same image converted to Web SWOP v2 or Gracol 2006 does not.
>
> I am unsure if this indicates a problem with the profile (either the
> file itself, how the target was read or the profile created), a problem
> with the press that the pressmen need to sort out, or simply the
> reality of what this press is capable of and the profile should be used
> as-is. This is my first attempt to profile the press, so I'm not sure
> if I've done something wrong.
>
> The press profile was created using the ECI2002 target. 15 sheets from
> across the press run were measured with an EyeOne Pro, averaged using
> ProfileMaker 5 and then a profile generated using GCR2 and a TIL of
> 300%.
>
> Thanks in advance for any advice or insight!
>
> Brian
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