Digital BW, The Print

Martin,

Thanks for an outstanding discourse on the posterization issue. You  had attempted to give me some insight into this area when I queried the group about it some weeks ago. I tried the solutions you suggested without a good outcome, and had reached the conclusion myself that, just as in the wet darkroom, there are certain images that you are just not going to be able to "make". I must say, though, at this point in my experience I derive much more satisfaction from images printed in the chemical darkroom. I know that this is largely a function of 25 years vs 10 weeks digital experience.

I am a physician and rarely get the opportunity to spend 4-6 hours in my darkroom. I love the fact that I can derive satisfaction and pleasure from even the few minutes a day I am able to spend "digitally".

Thanks for your expertise and willingness to share.

Stuart Spigel
  ----- Original Message ----- 
  From: Martin Wesley 
  To: DigitalBlackandWhiteThePrint@yahoogroups.com 
  Sent: Wednesday, June 26, 2002 1:30 AM
  Subject: Re: [Digital BW] Re: pshop 6->7 VM (converts file differently?)


  Todd,

  We have discussed all of your points at one time or another and I believe we
  are pretty much in complete agreement. Posterization can have many sources.
  The most common is probably over manipulating 8-bit files and I think the
  second maybe scanning.

  (By the way for those new to the subject, we use the word posterization to
  mean the loss of smooth transition from one tone to the next in the print.
  Areas that print out very flat or smooth areas that abruptly change tone.
  Posterization actually means a reversal of tone where instead of getting
  lighter or darker the tone actually goes in the opposite direction. You can
  get this extreme but it is rare.)

  My remarks about the RGB separation curve method and posterization come
  simply from looking at the histogram of a file before you apply the
  separation curve and after you apply it. From what I have seen regardless of
  the original condition of the image data there is less of it after the
  curves are applied. You can easily see this in the histograms or even better
  since you have a Mac there is a utility in the Files section of the Hi-End
  Scanner Group that gives you a count of the number of colors in an image
  file. Tyler check some counts before and after curve application and the
  count does go down after the curves are used.

  As we have noted before, when you do something to an 8-bit file that removes
  some of the 256 shades of gray it may or may not be noticeable in the print
  or on the screen. So most of the time we are okay. I think that we get into
  problems when the lost data falls in an image critical area or there is so
  much loss any sense of continuous tone is gone. So if you are walking the
  fence with an image and then apply an RGB separation curve you are more
  likely to fall into posterization.

  For those not familiar with the RGB separation curve and Epson driver
  method, a grayscale file is converted to RGB and a set of curves are applied
  to partition the ink so that the dark ink is used for the dark tones and the
  light inks are used for the highlights. With the MIS-VM inks this also
  controls the hue of the print. In order to fool the Epson driver into
  partitioning the inks correctly the RGB curves are often very severe and
  cause data loss. We would seem to be really torturing the whole system here
  since we take a grayscale file and send it to the driver as modified RGB
  data and the driver converts this into CMYK info to control the printer.

  I can see what is happening to the image data with this workflow. I have no
  idea what is happening to the data with the Piezo driver or a RIP. However,
  I assume that the Piezo driver is a CMYK driver but I don't know. The RIP
  drivers are CMYK drivers and theoretically it would seem likely that the
  data would have to be manipulated less than in an RGB/Epson driver workflow.
  This is purely assumption on my part since I have not experience yet. (I did
  pick up a copy of PressReady but have not had time to play with it.)

  My own system has been to use MIS-VM in a 1280 primarily with medium warm
  and warm curves. I scan in 16-bit and make initial adjustments there and
  then drop to 8-bit for final editing. I work in RGB using a soft proof
  profile. If I get posterization I try different curves, either earlier
  versions or different hues or switch between Paul's and Tyler's curves, to
  either eliminate the problem or shift it to a less objectionable tonal
  range. If that fails I will go back and apply the adjustments I have used on
  the 8-bit file to a 16-bit version of the file. If that doesn't work then I
  try a re-scan.

  I think bottom line some images don't work. They don't work in silver
  either. Sometimes a neg is just too flat in some areas to be useable.
  Sometime a digital approach will pull it out but not always. The key may be
  to have a variety of drivers and ink sets available just as you had a
  variety of papers, developers and toners in the darkroom. I have a second
  1280 that I have been using to try different ink sets. I would like to leave
  that set up with PiezoTone and keep VM in the other (I am considering
  switching to the Sepia-VM though). I need to set up a third 1280 then for on
  going trials but I am out of room. Adding a RIP for the VM and PiezoTones
  would further increase options.

  I think the multi-printer, ink set, driver approach is the way to go rather
  than trying to find the one perfect system. Different images are going to do
  better on one than the other. I generally like the Epson driver for sky and
  clouds, and the Piezo driver for images with lots of fine detail for
  instance. I think your remarks on the different ink sets have different
  transition points is valid and supports this idea.

  I can't match prints from MIS-VM and Piezo. It is just like trying to match
  silver prints on different brands of paper. You can get close but.... I
  certainly can't get a file that prints well with the Piezo driver and then
  print it out using the RGB/Epson driver without adjusting levels, etc. They
  just aren't that close. Since I have managed lots of posterization in prints
  using Piezo I can't recommend it as a posterization cure. The RIP's may be
  another story but I suspect you can mess up there too.

  Regarding the "pure" 8-bit print, I can only say that if it printed out with
  posterization without any manipulation being done I would suspect that
  either the scan was not good enough or the image itself was pretty flat,
  perhaps too flat. Also keep in mind that a posterized image can have a
  perfect histogram. If I scanned a posterized print for example, I would
  expect that the histogram would look okay.

  As you have pointed out before and I confirm, you can have files with
  terrible looking histograms that print out just fine. I think the reverse is
  also true. You can have files with really great looking histograms that may
  still print out with flat or dead areas due to a lack of info in the scan or
  the image.

  Well that ramble should have put most of you to sleep!

  Martin


  ----- Original Message -----
  From: "Todd Flashner" <tflash@...>
  To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
  Sent: Tuesday, June 25, 2002 10:09 PM
  Subject: Re: [Digital BW] Re: pshop 6->7 VM (converts file differently?)


  > on 6/25/02 10:31 PM, Martin Wesley wrote:
  >
  > > This has always been a tricky area and is the weakness of the RGB
  separation
  > > and Epson driver workflow. The application of the curves themselves in
  8-bit
  > > mode can totally trash your data. How do the PS6 and PS7 histograms
  compare
  > > prior to applying a separation curve? Is the problem occurring when the
  mode
  > > change is made or when the curves are applied?
  >
  > Hi Martin,
  >
  > Well, I'd like to see this explored a bit. As I don't have the Piezo
  driver
  > I can't compare, but you may remember a few weeks ago I posted regarding a
  > print I received from a friend which had the same problem (right down to
  > dark skin - or at least light skin in shadow) but, A) the print was from a
  > file that had no manipulation done in 8-bit mode, i.e., had a "pure"
  > histogram, and B) was printed through the Piezo driver. Still,
  posterization
  > (or something close enough to it to be called that) was present.
  >
  > Now, please don't misinterpret my interest. I don't know that I'm trying
  to
  > prove anything per se - if the Piezo driver/workflow were to consistently
  > prove itself better I'd just go and buy it, and I may just do that in
  time,
  > (but that's not what I've seen so far). Anyway, I am interested in
  > understanding this. Sooo, when you say it's a weakness of the RGB
  workflow,
  > do you in fact mean: as opposed to the Piezo workflow; or do you mean it's
  > the weakness of any partitioned workflow. Have you (anyone) tried the same
  > image side by side through the two different workflows and compared?
  >
  > What I'd consider a side by side test would be to work the file fully in
  > grayscale, then dupe it. Send the original to the Piezo driver to print on
  > say EAM with that profile, convert the dupe to RGB and apply a good EAM
  > curve to it and print through the Epson driver.
  >
  > Similarly, I take your point, which was that the posterization may be
  caused
  > by working a file in 8-bit mode such that it wont appear to be damaged
  UNTIL
  > you apply the separation curves. This too needs be side by side tested by
  > also working the same file in the same way in 16-bit mode and printing
  from
  > that, and comparing. Consider also that the Epson driver includes
  Microweave
  > and/or Error Diffusion, which may (throw salt over my shoulder) help with
  > broken files.
  >
  > Anyway, sorry to be so intense, but this topic has bedeviled me. While
  > struggling with my own occasional posterization I believed all the
  > conventional wisdoms about the sources: bad curves, overworked files,
  > misapplied driver settings...all very properly the first things to rule
  out.
  > But then what? When we've ruled out the first suspects, when a person uses
  a
  > good scanner, does no 8-bit editing, uses the Piezo driver with the right
  > profile, etc, and they still get posterization, what does it tell us?
  >
  > And it always seems to be in the 3/4 tones, no?
  >
  > I just wonder what it is in this process. I'd love for someone who has the
  > piezo driver to make the comparison sometime. Take a file that posterizes
  > through one workflow - any workflow - and then do the same file through
  the
  > alternative workflow and see if it helps. If it does I'd say stick with
  the
  > workflow that helps, until you get posterization with it. Then try the
  > alternate workflow and see if it helps. My suspicion is that no one
  workflow
  > will out work the other in all cases. I'd bet it's good to have two
  > workflows available precisely in case you hit the wall with one, you'll
  have
  > somewhere else to go.
  >
  > Someone mentioned it's probably the way tones in some images fall relative
  > to the transition between ink densities. That sounds very plausible to me,
  > and it would explain why it is common to Piezo and Epson prints, and 8-bit
  > and 16-bit files, and some of our prints get it while others don't. The
  > irony is (while it's certainly a blessing in other ways), all the carbon
  > pigment inksets seem to be increasingly built around the Piezo densities,
  > which means switching inks/workflows becomes less likely to change
  anything.
  >
  > Todd
  >
  >
  >
  >
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