Digital BW, The Print

On 06/01/2012 02:31 AM, Paul wrote:
> What I have to watch with my DataColor unit is my lifting the meter too
> soon. The way I know I've done this is that the color values (Lab A and
> B) will spike in one direction or the other -- way off the trend line. I
> see this when I'm looking at the graphs in Excel. What I do to correct
> the problem is simply go back and remeasure the patch correctly. I
> simply write the new, correct values into the Excel boxes and save the file.
>
> Paul
> www.PaulRoark.com


It is not that different with an X-Rite Eye 1 Pro. I count to three on 
each patch before lifting it. I also think that one should try to keep 
gloss paper patches as flat as possible under the spectrometer, the 
geometry of the spectrometer optics is not an ideal Ulbricht sphere but 
a practical compromise that works very nice with matte papers but less 
so with high gloss papers. Targets printed and dried fast with a hair 
dryer and then placed on more sheets of the same paper for measuring 
should be pressed firmly with the meter to get that patch flat.

There is another way to get the Lab b on a zigzag course. Measure a 
target with heavy bronzing and the 45/0 degree reflection optics in a 
spectrometer are affected by the bronzing layers. The measured color is 
not 1:1 to what the eye sees in color of the bronzing but that is 
understandable given the spectrocam's light source and sensor as another 
light + another observer. In practice one would not select a B&W 
paper/ink combination that creates that much bronzing but in color 
printing it may be less obvious and play a role when colors are off 
after profiling. Grey range in color prints for example. I will put some 
QTR linearisation plots on my site to show the difference between a 
target with and without bronzing.


-- 
Met vriendelijke groet, Ernst

Dinkla Grafische Techniek
Quad, pi\ufffdzografie, gicl\ufffde
www.pigment-print.com