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Re: Epson or HP for alt-phot ... ? (some OT)

Dave Soemarko wrote:
> ... if one wants to do some kind of image editing (burning, dodging,
> etc), then it is good to have the monitor calibrated to at least approximate
> the look of the final print. 

Agreed, and consistency would be much more important than absolute
calibration.

> ...
> There are problems with using full range. ... physical problem... tone
> mapping... gamma ...

I am not so sure about this.  I have determined the amount of ink to
give maximumn white.  I am determining the threshold amount of ink to
remove from that to give maximum black (around 40% with current
settings, there is no 0).  Both white and black are judged from a Pt/Pd
print.  Any values inbetween can be adjusted.

I may not use the gamma function as I may use a set of curves to correct
for contrast adjustments.  But I will keep the "0 problem" in mind.

> ... what you are doing is closed-loop calibration which is basically the
> same thing as working with tone-reproduction curves except that you use rgb
> values rather than density values. ...

A major difference is that I am doing all adjustment and control in CMYK
not RGB.  (The first thing I do is convert the scanned RGB into CYMK.) 
This is to control the amount of each ink rather than having it
calculated from RGB.  I do not use the cyan ink because it has shown to
be near transparent for Pt/Pd printing (other manufacturers may vary). 
However the cyan component is merged with the other components using the
channel mixer (MYK).

> ... the desired reproduction curve is not really linear. 

Definitely not linear.  The use of three inks might help get better
tonal discrimination where needed.  Separate levels and curves are used
for each ink.  I have concerns that the ink may not be able to be
delivered into enough tone producing steps for the Pt/Pd process.  I
hope the equipment can handle this.

> ... as I posted about 2 weeks ago, after you are done, you might
> get something that Photoshop is already giving you ...

I do not know what this might be.  One proplem that I find is that
Photoshop does or tries to do too much.  For example, when requesting a
custom color, Photoshop changes the inks to print what it thinks to be
the color, not what I want.

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/