QTR-Quadtone RIP

Hi Howard,

I might just be repeating what others have written, but I'll send this anyway in case it 
might help.

I'm pretty new to this whole process and ran into the same situation.  So, in regard to 
being new at it, if anyone sees anything that I suggest, that might be a little off or could 
be clarified further, don't hesitate to do so.

What I've found is that if your assessing the ink limits by eye, you're going to want to look 
for an area where the paper is covered and subsequent patches level off as far as getting 
darker.  Granted that still leaves room for interpretation, but it might get you a little 
closer.

Now, if you have access to a densitometer, a spectrophotometer or at least a reasonably 
decent scanner with an image editing program capable of working in a Lab color space, or 
a scanner capable of reading L values (sometimes there is a "densitomer" feature capable 
of doing this, that can be used in the scanning process) you can approach it a little more 
"scientifically."  Basically what you would want to do is measure either densities or L values 
of the patches, then determine numerically, where the values level off.  I personally have 
been using my Epson 4990 scanner and Photoshop to do this.  I basically just scan the 
image into Photoshop, convert the image to the Lab color space, then do the reading with 
the color sampling tool set to average the value of a 5x5 pixel area.

As for setting different limits, I've only been able to do so, when creating the final profile. 
So in order to determine the relative values, ie: dark grey = 50% black, I've just taken 
whatever patch I determined to be the ink limit for the different gray values and compared 
that to a print out of a temporary, black only profile (created by indicating only one "gray" 
ink, and setting the rest as unused), since I haven't been able to do the separation page 
with a new general ink limit (actually if anyone could fill me in on that one, it would be 
helpful).  However, I should note that, following this procedure I've had great results, in 
that you can then determine whatever limits you want for each ink and maximize your ink 
usage.  For instance, I'm using an Epson 1280 with Piezotone inks, and have regularly 
found that the black ink, maxes out long before the other inks, so I create the black only 
profile with the black set to say 55%, print it, and then compare that (by scanning into 
photoshop) to the original ink separation printout to find the relative values with the inks 
that often max out around 85-90%..

Anyway, hope all that helps.

Regards,

Eric