Piezography posterization with chromogenic film

I'm struggling to get consistent, non-posterized results from

chromogenic B&W films using a Nikon ED 8000 scanner and printing with

Piezzography Warm Tone inks on Hahnemuhle Photo Rag. It's an issue

with portraits where my three year old daughter looks like she's got

a worse five 'o' clock shadow than Bluto (or Desperate Dan if you're

a Brit), I'm not too happy but she's really angry!

I've tried all the obvious remedies like turning off ICE and

confining tonal manipulation to Photoshop. I'm scanning medium format

negs to Photoshop 7 at high bit depth with very modest curves and

gentle sharpening. I've had the same problem with colour negs

converted to B&W but there's never a problem with silver based negs.

Any suggestions?

Thanks, Gary

Gary,

How does the stepwedge image that was on Piezography disc print? The supplied profiles are not a perfect match for the newer warm tone inks and some adjustments are necessary - usally this just involves making a new custom greyscale preview in Photoshop. Do you have a decent preview set up for this paper/ink combination?

What do your histograms look like for your trouble images, esepcially for the tones that are posterized? Do these trouble areas match up with any flatness in the same tones in the stepwedge print?

Tony, thank you very much for your answer.

The 21 step wedge printed OK but not great, there was a slightly harsher jump at about the 30-40% level than with the other levels. The histograms all looked very good, no comb effect at all. I'll try making another profile, but that's right at the edge of my own expertise, are profiles commercially available anywhere?

What about "dot gain"? I'm clueless as to its function in a digital environment but that little square on the interface keeps staring at me saying "go on, PLAY WITH ME", but I know that if I do, I'll just wreak irrepairable havoc with the entire system!

Regards, Gary

Gary,

I was about to provide a reasonably lengthy reply but Jon Cone has said much about this in a recent post to the Piezography list. I will include it below for you. It is unlikely that you will see any more profiles being written for the Piezography software as Cone has parted ways with the original developers of the software. This shouldn't really pose a problem if you follow the simple instructions which Jon often repeats. I'm not sure if you are using a properly calibrated workflow with a calibrated monitor but that is key to getting good results with images that you are adjusting visually on screen. The Piezography manual provides excellent instructions on calibrating your monitor in Photoshop for any paper/ink combination (by setting a custom greyscale dot gain curve). It might be worthwhile to review these instructions.

Jon Cone posting from the Piezography3000 list:

"Lets make certain that everyone understands how to use ICQ profiles.

ICQ profiles are not ICC profiles and the software does not employ anything like a simulation CMM. You can not expect an image to print the same on two different printers such as the 1280 and 3000, let alone a 1200 and 9000, or a 980 and an 1160. They just do not work that way. All these printers print remarkably different from each other using the system.

The profiles do a very good job of linearizing inks. They do not equalize the process from one printer to another.

But the workflow of using profiles is NOT to edit an image and then try and bring that same edited image back to other papers or printers!

Workflow:

1. Print out a 21 step image on desired paper using the ICQ profile.

2. Create a custom Photoshop Grayscale Preview.

This Preview is saved for future use. Previews are created for each printer/paper/ink combination.

3. Using the Preview, adjust a new image to suit.

4. Save the original image as well as the edited image.

5. The edited image is printed through the profile and matches the monitor.

6. The original image is used for other printer/ paper / ink combos.

If you do this, ICQ profiles are very compatible. If you do not, you will have trouble shifting papers, printers and inks."

If you've got a problem with chromogenic and color neg, but not silver neg, then the problem lies in your scanner, not your printer, although it may be that the linearization process for the printer may exacerbate the problem.

Color neg and chromogenic B & W have low inherent contrast, and thus "fill" less of the scanner's available bit depth, especially if they're a little underexposed. Thus, bits "lost" through manipulation later in the process, including the lineariztion step, are more likely to push you below 8 "good" bits and into posterization. Try scanning the B & W as color do all your corrections in 16-bit color, then convert to B & W, then to 8-bit to print.

Overexposing your film a stop in the future might help too.