ICC Profiling Problem

[Ajay Tanna]

I have successfully worked with creating & proofing with ICC profiles with several RIPs. One strange thing I notice is posterization in custom ICC profiles. This I have noticed with both HP Designjet 10PS & Epson 1400. Repeated charts & profiles yield nearly the same result. I still see red gradients not smooth and bitmaps have posterized highlights in things like red flowers or apples with areas which are supposed to blend in smoothly stop suddenly with sudden transition into yellow white or grey. This happens only in areas with predominantly Magenta & Yellow in the image. I must have built at least more than 15 profiles. I am still stuck. Please help

[zedonet]

Did you reduce ink saturation as suggested? If this is already the case I suggest to set the ink limit for profile chart printing to 250%.

Which software and spectrophotometer do you use to create your profiles?

[Ajay Tanna]

Hi,
Thanks for the help. I use Gretag Macbeth Eye-one pro with Profilemaker Pro software. I have indeed changed saturation to 70% as advised earlier but left ink limits at 150% on all trials I made. Though I tried one test chart by changing the saturation back to 100%. But the posterization in Red is still there.
I always use the ECI2002 test chart in Profilemaker & it has always worked. This time I tried the IT8.7-3 chart with 1100 and a few odd patches and the profile was smooth and all the Red posterization was gone. But the colors were incorrect. I have a test image which contains a photo of the GM Color rendition chart among other things that I print to check profiles. The colors on these are all wrong when I profile with the IT8.7-3 chart, but perfect when I use the ECI2002 chart but have Red posterization.
I tried to post-linearize the problem profile in GM Profile editor. Again the posterization went away but all grays become much redder.
Today I took everything to a friend's repro shop who uses Monaco profiler on a windows setup. I only managed to try with 917 patches with pre-linearization. The result was absolutely same as Profilemaker with IT9.7-3.
Tomorrow I will try your suggestion of changing ink limits to 250% and saturation 70% with fresh ECI2002 chart
The built in profies with PrintFab are absolutely fantastic. How do you do them. Seems like black-magic to me.
Thank you

[Ajay Tanna]

Hi,
That last bit of advice from you seems to work. I set saturation in the file at 70% and in the PF Toolbox ink limits to 250%. Then I printed a target of 1485 patches and profiled it. Indeed the prints were magically better. The posterization from red is completely gone and the prints are super sharp. I can see details which Heidelberg Speedmaster 4 color press (of 2006) was not able to reproduce at 175 Lines. There is some posterization in Green, but this could be due to profiling error as I did not have time to further investigate. This I see only in one radial gradient (vector) printed from illustrator CS3. Other test charts like ECI PDI etc., have no posterization whatsoever.
This makes Printfab finally a very usable product and in a few days I will shop for the license to make it permanent.