QTR-Quadtone RIP

While I am waiting for my shipment of MIS Eboni ink, I thought I would play with creating a curve.  I wanted to try getting the photo black ink to print on glossy paper.

I fillowed the instructions for this, and set the ink limit (60%) and then scanned the 21 step reference print out, and entered the linearization values.

I then printed out a reference grayscale photo.  I was viewing it at gray gamma 2.2 on a reasonably weel calibrated monitor.  I found that the darks on the pront were lighter than the darks on the monitor, and the gamma was a little too light (maybe due to the darks not being dark enough?)

So I just increased the darkness of the darkest shades and lowered the gamma from 1.0 to 0.9.  I then printed the picture again and I got a decent result.  Quite close to what I had intended.

I did have some rather strong metamerism visible on the 21 step printout.  It was pretty neutral up to 60, then it took on a warmer hue until 80 where it got neutral again, then went warm  at 95 and more neutral at 100.  A very interesting effect and also visible in the areas of gradual shade changes in my test photo.

I guess I will have to avoid using the photo black ink and only use the MIS Eboni for my B&W prints.

-Tony

Update:

I uploaded the curve files to the FILES section.  I am trying to gain some proficiency in creating curves using a scanner to give me some measurements.  Please take a look at it and see what you think of the curve?  If you have an R1800/R800 with the Photo Black in the usual place try printing it on some Epson Premium Photo Glossy paper and tell me what you think of the appearance?  Does it seem right?

I had a couple of experimental curves for this.  On one I tried to get fancy.  I used my Epson 2400 scanner and an IT8 reference card.  I scanned both the IT8 and the 21-step printed image (with no linearization values, just the 60% ink limit).  I then used Photoshop to make a curve layer in the scanned image to get the L values of the IT8 to be correct.  Then I measured the L values of the 21-step print and entered those values into the linearization table.

The printout I got using the linearization was clearly wrong.  The 5% step was barely visible as something other than paper white.  So I guess that idea is a bust. 

For the curve I uploaded, I just scanned the non-linearized print, and set the paper to 100 lightness and the blackest as 0 lightness, and let everything else fall where it may.

Any suggestions?

-Tony