Digital BW, The Print

plnelson2003 wrote:
> 
> You've mentioned the metamerism problem
> several times.  But metamerism is a physical
> property of the ink. When any two inks have
> a different shape to their spectral response
> curves you have the risk of a metamerism.
> Pigmented inks tend to have "peakier" response
> curves so they have more risk of metamerism
> than dye-based inks. Are you saying the dark
> cyan and dark magenta inks have a response
> curve with a different shape than their light
> cousins, so that eliminating them fixes the
> problem?

I suspect the dark cyan and magenta are not used by IP because they're just not needed to produce a neutral print.  I think the key to reducing metamerism is not using the yellow ink.

My tests consisted of printing Paul Roark's step wedge using both IP and various settings of the Epson driver at 1440 dpi.  I then scanned the 1% patch at 1600 dpi and sharpened in photoshop so I could clearly see the individual ink droplets.  I'm working on an article describing the tests and the results I've seen, but it may be some time before I have a chance to finish it.  I have several other commitments at the moment that are taking a good portion of my free time.  I'd be glad to post the scans to the file area of this forum if there is interest.

It appears that the light cyan and magenta are all that's needed to neutralize the black and gray inks with plenty of headroom to produce tinted BW prints using IP's tint picker.  I've not tested any tinted prints to see if yellow is used.

My "standard test" for metamerism consists of evaluating Paul Roark's step wedge under daylight, tungsten, and flourescent.  I have a nice big window in my office and by simply tilting a print back and forth from the window light to the office flourescent lights I can see the color shift from magenta to green.  I don't see this with the IP prints.  I don't know of a more scientific test for metamerism that I can perform cheaply.

--Tom