Re: Color Value


"Dirtroadie" <DirtRoadie@xxxxxxx> wrote in message
news:1131724601.948897.281480@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> Bob Headrick wrote:
>> "Dirtroadie" <DirtRoadie@xxxxxxx> wrote in message
>> > Or in another way of looking at it, if I created a block of solid color
>> > in a Photoshop image, what RGB or CYMK value would I assign so that it
>> > would print out using a single "photo" inks and no other inks?
>>
>> I think you would have to experiment. At least for HP printers it would
>> depend
>> on which printer model and what driver and paper type is selected. The
>> photo
>> inks do not directly map to the CMYK values in Photoshop.
>
> Thanks, while that doesn't answer the question directly it is useful
> information.
> I suspect that the same must be true for all printers. And of course
> any tweaking of the actual color settings for a given printout will
> change the nature of the applied inks too.
>
> As to "experimenting," I am hard pressed to determine a way of
> assessing which inks are applied to the paper under any given set of
> circumstances. My goal was really just the opposite - to actually
> control which inks are used. That may be well beyond the scope of
> anything which is feasible without knowing how to control a printer
> directly such as is done in a typical "nozzle check" printout
> controlled by the driver for a given printer.

This is certainly more difficult than it sounds like it should be, but I do not
know of an easier way. The control codes to directly control the nozzles are
not typically publicly documented, at least for the HP printers I am familiar
with.

As for the method of trial and error, for cartridges with integrated printheads
and ink supplies (such as the HP #57/58) you could do the following rather
laborious procedure: take two pairs of cartridges. In one set deprime the
cyan and light cyan (or the light magenta and magenta). Now print color ramps
from Photoshop, using the good color cartridge and the deprimed photo
cartridge, then with the good photo cartridge and the deprimed color cartridge.
Using a microscope find which color shades correspond to the desired pure
color. Be aware that some printers have additional capabilities to self
calibrate for differences between drop size of different cartridges and other
factors. This would further complicate things....

There is probably a more straightforward way to do what you want. What is your
actual application?

Regards,
Bob Headrick


.

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