Effect of CGO on print density


Question 1: How does CGO impact the L* of dMax? Question 2: How is paper white L* impacted with addition of CGO?

Since I’m covering complete 8-1/2 x 11 sheets with CGO when the linearization targets are about 3 " tall , is there a way to linearize without CGO then add it back in? Not only would I conserve CGO, but I would cut my first linearization from 3 sheets per paper type to 1 sheet.

Question 3: Can you overprint CGO with ink?

I was planning on putting 3 targets on an 8-1/2 x 11 sheet, but once I printed the top 1/3 page, the entire imaging area of the page was coated with CGO. And the print failed when I did a custom paper size of 3.67x8.5. Not sure what the minimum paper length is; it will print 3x5’s but I assume that’s in portrait mode.

  1. GCO does not impact the L*.

  2. Paper white L* is not impacted except for the slight OBA blocking of GCO (this makes the paper more archival BTW).

2.5. Yes. Simply print with one of the NoGCO curves for linearization.

  1. You can overprint but the result will not always be predictable on some paper surfaces. GCO and Pro ink were built to work together and not separately.

3.5 Super small custom papers sizes can fail on many epson printers.


If I linearize with the NoCGO Curves, is it an easy process to add CGO to that Linear NoCGO curve?



Yes. Simply copy the 256 rows of numbers under “# LLK Curve” in the normal curve and paste them over the 256 zeros under the “# LLK Curve” in the NoGCO curve.


This type of editing is explained in the Advanced Topics section of the manual.





In performing that process, I observe that the values for GCO vary with paper and tone curve (cool, neutral, and warm). Does this mean a different volume amount of GCO is laid on top of the cool ink at 2 different density points? And that amount is different for those same two density points of perhaps neutral and warm? And baryta may be different than platine?


No. The difference is only because of linearization and not the total ink load. So the same amount of GCO is still applied from paper to paper.



Are you saying that the 256 lines of code for the LLK channel, are changed with linearization? From a previous post, I have the understanding that GCO doesn’t effect linearization, and that I could linearize a NoGCO curve then copy the 256 lines of code from the LLK and paste it over the zeros in the linearized curve to create the new linear curve for that paper.

If the GCO curve is changed, is the change insignificant as far as impact on the linearization of the entire curve set for that paper?


When linearization happens to a curve, it shifts the values left and right (related to how the curve looks in QTR-Curve-View). The GCO channel is effected as well (just because it is there) but this has no effect on the total GCO amount or L* values of the print.