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Digital BW, The Print

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Clipping in the QTR V2 profiles

Clipping in the QTR V2 profiles

2005-02-19 by ferdinand_paris

Following up on a recent post, I have been mucking around setting the
black print point on my Epson 2100, using the chart at:

  http://www.zuberphotographics.com/page_BlackPoint.htm

Using EEM & UC, the black is actually zero.

However it shifts when I print using QTR, and it shifts quite quite a
lot when I use the V2 QTR profiles in Qimage.

If I convert the Zuber test chart to QTR-RGBMatte in PSCS, then all
values from 0-3 are compressed to zero.

Roy or whoever: Is this clipping an unavoidable byproduct of the
linearisation or whatever?

~~~

The problem gets a worse if I use Qimage.  If I run the same test
chart through Qimage and convert it to QTR-RGBMatte, then the darkest
value is 2 rather than 0.  In addition, all values up to 10 are
clipped at this 2 level.  In other words, the clipping is worse when
using Qimage, and the darkest two output levels are not used.  

Why is there this much clipping in Qimage, and why the 0 and 1 black
levels are lost are questions for Mike Chaney, or perhaps more
appropriately for the author of LCMS, and I've posted them in the
Qimage group.

F_P

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