Friends-- With some trepidation I revisit this subject of the best blocking color (or ink combination) for smooth tones on digital negatives. And before I describe my tests, here are a couple of background items:
First, I am convinced Epson has changed the formulation of the inksets it supplies for the 3800 and for the 4880, sometime in the last year or so. In the old K3 inkset (as I used on my 3800) the strongest UV absorbers were dark black (pK or mK), Y, and LK. But C, M, LC, and even LLK were also significant absorbers and were useful. In the current K3 inkset only dark black (either pK or mK), Y, and LK are significant absorbers with the rest being at least 10-fold less absorbant. I have recently purchased the 4880 which uses the K3 inkset with vivid magenta. That inkset is very similar in UV absorption to the current inkset for the 3800. So, Epson has significantly degraded the ability of its inks to absorb UV. But I find we can still make good negatives with what is left.
Second, everything I have to say is only applicable to palladium emulsions. I have not tested any other.
Third, I have tried these ideas on both the 3800 and the 4880.
Now to the smoothness tests. In Photoshop I made a grayscale gradient 10 inches long by 2 inches wide, from 50% gray to 0% gray (white). Using QTR I then printed negatives of this gradient using different ink combinations. Of the various combos tested only three were really informative.
First I wrote a profile to print the gradient in just two inks, Yellow (70% ink limit) and Cyan (20% ink limit). (I attach the ink chart of this profile below). I printed this negative on a pure palladium emulsion. The print had two problems. One, as the print gradient got darker (ie, the Yellow ink dots were spaced further and further apart) the tones got rather grainy. Two, and a bit of a surprise, there was objectionable banding, parallel to the direction of the print head. So this pure green gradient negative flunked on both counts.
Second, Colin Graham kindly sent me a profile that prints without using any dark black ink but uses all the light inks except LM. I made a negative of the gradient with Colin's profile and a palladium print. This made a much improved print. The medium dark tones were much less grainy and the printer banding was greatly reduced (but not eliminated -- it would still be bad in a medium gray sky). If you look at the ink chart for this profile, I would attribute the improvement to the fact that the light inks are filling in around the Y and C inks. So I do not see this as a "pure green" profile.
Third, I printed the gradient negative using my current palladium printing profile for the 4880. The ink limits in this profile are:
pK 35 going to boost 55, C 25, M35, Y35, LC 35, LM 0, LK 40, LLK 40. As I said earlier, I think pK and Y are doing most of the lifting for the dark inks and LK for the light inks. To my eye the print from this negative was just as grain-free in the high tones as Colin's profile and printer banding was not visible.
OK, maybe adjusting my new 4880 would also help the banding (I will have to try) but clearly using multiple different inks will also cure it. As to grain, I have yet to find any ink combo that is more grain free than the semi-balanced inks in my current working profile. Another comment, I got printer banding on my old 4000 when I wrote profiles using only K and LK inks. The banding disappeared when I started using all of the inks. This seems similar to what I now see when I use primarily the Y ink.
OK guys and gals -- have at it. I expect my experience is not what others are seeing. But it is what I see and I can report no other.
Cheers, Ron Reeder
