Digital BW, The Print

In response to the comment on the "just use ABW" from the "another drawback of coated paper" thread:

Earlier last year I was asked to write a few chapters on printing for a digital black and white book, and started making comparisons with different printing methods. The book project fell through, but I had the tests done and made the following blog post a few days ago along with scans of actual prints and density measurements: http://www.bwmastery.com/blog/2015/abw-vs-qtr

I realize that some people see the the straight line curve as a drawback of QTR, but I see it as a huge benefit. By controlling how much more ink goes into the shadows and still having them separate you can have the appearance of dark/rich shadows that smoothly transition into pure black, rather than a noticeable jump like moving up the black point with a levels adjustment. This QTR approch has a similar visual affect to a gamma 2.2 adjustment, but doesn't crunch and compress the last bit of shadows. It does require controlling the tones in the original file and not using a blanket correction curve, but the resulting prints look almost identical to the screen and don't usually require additional ICC profiling or color managed printing. I also realize that you can create ICC profiles to correct for some of the problems with ABW, but if you are going to do that you might as well make your own (or use) QTR profiles and create ICC profiles for them instead.

I am now writing a post about comparing prints made QTR and Epson K3 inks, QTR with Eboni-6 and my QTR profiles, Piezography Carbon K6 prints I made, and Selenium and Warm Neutral K7 prints that Jon Cone made for me last year as comparison prints to use in the book. It might take a few weeks depending on how work projects go though.

Richard Boutwell

I think you have missed the essence of QTR Create ICC.  QTR with a QTR profile is not a straight line density function.  The whole point of developing QTR Create ICCC was to address this very fact.  I'm not sure that the forums archives go back far enough but if you were around in '05 you may recall the conversations in which I was a significant protaganist which led Roy to develop Create ICC. Until then, people using B&W rips (including QTR) were indeed applying a linear density function to their prints and this lead to issues such as shadow compression and complaints of "overall lighter prints" than on screen. Draw a straight line between an imperfect black and an imperfect white and it's obvious this is the result.  Roy brought gamut mapping to the B&W world by applying techniques long used in the colour domain for black (and white) point compoensation.

Epson was aware of the issue of applying a linearised density ramp to a print when they made ABW. They embedded non-linear gamut mapping in ABW but of course hard-coded it to the selectable Epson ink and paper combinations. Roy's QTR Create ICC was a better solution.  It allows the technique to apply to any ink and paper combination (not just Epson) and, of course, for any individual printer. It has significant add-on benefits including the ability to preview images with their 'colour' toning on screen and to be able to post or send an image in digital form with this 'as when printed' toning.  When applied to Epson ABW printing it improves this as well.

All the best

Steve

On 29 Jan, 2015,at 04:05 PM, "richard@... [DigitalBlackandWhiteThePrint]" <DigitalBlackandWhiteThePrint@yahoogroups.com> wrote:

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> In response to the comment on the "just use ABW" from the "another drawback of coated paper" thread: 
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> Earlier last year I was asked to write a few chapters on printing for a digital black and white book, and started making comparisons with different printing methods. The book project fell through, but I had the tests done and made the following blog post a few days ago along with scans of actual prints and density measurements: http://www.bwmastery.com/blog/2015/abw-vs-qtr
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> I realize that some people see the the straight line curve as a drawback of QTR, but I see it as a huge benefit. By controlling how much more ink goes into the shadows and still having them separate you can have the appearance of dark/rich shadows that smoothly transition into pure black, rather than a noticeable jump like moving up the black point with a levels adjustment. This QTR approch has a similar visual affect to a gamma 2.2 adjustment, but doesn't crunch and compress the last bit of shadows. It does require controlling the tones in the original file and not using a blanket correction curve, but the resulting prints look almost identical to the screen and don't usually require additional ICC profiling or color managed printing. I also realize that you can create ICC profiles to correct for some of the problems with ABW, but if you are going to do that you might as well make your own (or use) QTR profiles and create ICC profiles for them instead.
>
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> I am now writing a post about comparing prints made QTR and Epson K3 inks, QTR with Eboni-6 and my QTR profiles, Piezography Carbon K6 prints I made, and Selenium and Warm Neutral K7 prints that Jon Cone made for me last year as comparison prints to use in the book. It might take a few weeks depending on how work projects go though. 
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> Richard Boutwell
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Since I am the commenter referred to, I will reply.  B/W printing is a  
very small part of my life.  Altho I am retired, my major hobby is field  
trialing and hunting with fly fishing next in line after that.  I field  trial 
Field Dog Stud Book (FDSB) English Pointers (short hair, long tails  NOT 
German Shorthairs) and American Kennel Club (AKC) English Cocker  Spaniels.  From 
time to time, I judge FDSB field trials (mainly  English Pointers and E 
Setters).  When I print, I don't want to fool around  on a computer, I want to 
PRINT.  ABW lets me do that.  Altho, as I  said, I'm not aiming for museum 
quality, I feel that I know a decent print when  I see one (and as I posted, 
my sales to professional dancers and the use of one  of my pictures on a 
magazine cover gives me the confidence to say that.)   And I was misquoted.  I 
did not say, "just use ABW", i believe I said, "I  just use ABW."  The rest 
of the world can do whatever suits it but ABW  suits me, so my advice is 
MYOB and I'll mind mine!!  
 
 
In a message dated 1/29/2015 11:05:08 A.M. Eastern Standard Time,  
DigitalBlackandWhiteThePrint@yahoogroups.com writes:

In response to the comment on the "just use ABW" from the "another  
drawback of coated paper"  thread:

I don't have time to post here much if at all lately but your post caught my eye.  There was a very old thread called tonal range and linearization - or something like that.

Plot a line from (0,0) to (100,100) and call it L* (LAB colour space, denoting luminance).  If you prefer, cut the x axis into 8 bits 0-255 or 16 bits if fanatical.

Now on the same chart, plot a straight line from, say, (0,14) to (100,97).  Dmax = L* of 14 and paper white = L* of 97, something like matt paper.  Change the numbers if you like but hopefully you get the point. If you have linearised your printer L* output luminance production will be a straight line from ink black to paper white.  (That is afterall what linearisation is.)

Now look at this line in comparison to a perfect L* plot (with it's perceptually close gamma, not far from 2.2 blah blah blah).  How much is lighter than perfect?  How much is darker? If you want, plot a third line with a better black and brighter white - label that one your very good Eizo display.

The challenge of colour management (all parts of the chain: file to printer, file to display etc) is how to transform a file from perhaps an imperfect capture colourspace, through a perfect working space and on to an imperfect output device/space. The ball starts rolling with black point compensation and white point compensation.

We tend to ignore using WPC when previewing prints on a display because our eyes are very good at adjusting white point.  But if you want a sense - on the display - of the lack of black you do need to use BPC.  Yet, most of us likely hate the shock we get and just leave it for the print itself.

If your B&W image is sent to print as a colour file with 'normal' colour management ICC profile (we all hate this because of the bad use of colour ink in the greyscale but let's bear with it for a second) an intrical part of the mapping from file space to print space is the adjustment for the black point and white point of the ink/media as recorded in its ICC profile. You can read various Adobe tutorials as to how the file numbers are adjusted for this BPC/WPC. With B&W printing and particularly to matte paper it's the BPC that affects us most because, while getting better, dMax is still wanting.

So the challenge is/was how to map into a compressed/constrained gamut and a straight line linearised L* doesn't do the job very well. What BPC does is resurrect a better gamma around the mid tones. Of course that means something needs to give and, yes, as with colour printing, BPC means some compression most notably in the shadows because that's the part that's far from perfect.

Even though Epson ABW printers are well linearised when they leave the factory, plot a step wedge with ABW and plot L*.  You'll notice it isn't a straight line.  They've embedded some BPC/WPC.  It changes with paper selection. They get it.

What QTR Create ICC did, in short, was to take this 'greyscale colour management' and apply it to greyscale printing i.e. take the luminance management and ignore the a* and b*. Think of it colour management of L*. It does the same gamut mapping we use all day long but, of course, only with respect to luminance.  BUT one of the tangential cool things about the files was that it could also capture the a* and b* information of your printed step wedge.  This allows proper tonal proofing and the ability to impound that tone on a digital copy of the file for electronic distribution / posting on the web etc. (You can post those cool warm tone images of majectic lions or cheetahs overlooking a windswept plan and with incredibly ominous and heavily manipulated clouds looming overhead.  They just don't look as cool if they're perfectly neutral and they wouldn't match the toning of the book you intend to sell millions of copies of.)  You can print a step wedge with your favourite ABW settings (or whatever RIP you prefer), measure it and not only use the QTR ICC profile to do the luminance mapping with a CMM but preview the tone while you edit the image.

Genius.

Of course then Apple and Adobe decided to throw in some speed bumps in the way they managed colour management but these were easily overcome. (Perhaps they have thrown up more but I haven't printed for quite some time now.)

HTH

Steve

On 29 Jan, 2015,at 08:30 PM, "richard@richardboutwell.com [DigitalBlackandWhiteThePrint]" <DigitalBlackandWhiteThePrint@yahoogroups.com> wrote:
> Steve, I tried going back to look at the original posts about the push to get QTR-Create-ICC built, but I could only find entries after it was already released. But could you elaborate on what you mean by "draw a straight line from an imperfect black and imperfect white"? By imperfect do you mean paper white not being 100% reflective and whatever the inks' D-max not being 0% reflective?
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> If you look at the pictures in my post, the first one is a down sampled file used to make the resulting prints (gray gamma 2.2 converted to sRGB) and is essentially identical to the QTR print with no color management. What I find when using ABW, or QTR and an ICC profile, is that the prints always have compressed shadows. In theory and computer maths that might be what is supposed to happen, but for me, it doesn't make a better print.
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> Which is to say, I understand the reason for using the QTR ICC profile workflow, but I choose not to for printing black and white (printing color is a different story). This decision is based on how I build my profiles and observing the effect printing with ICC profiles has on the actual print (which sounds like a case of "it works for me"). The approach I take comes from growing up printing on Azo and then platinum/palladium and being accustomed to the long straight line with rich blacks and smooth open shadows—there might not be "detail" in the shadows the print has a rounder and smoother three-dimensional feeling. When I translate that to inkjet printing: Using QTR with an ICC profile (and rendering intent with black point compensation) or the Epson ABW driver setting that causes the tones to stop increasing smoothly from 95% through 100%K and the resulting print has feeling of flatness even though "more black" is supposed to give the appearance of more contrast. I want to go back and reread Keith Coopers' review of the new Epson printer from last week. I think he addresses some of this there. 
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> Ok, I'm getting back to work. Those scans aren't going to retouch themselves. . . 
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> Richard Boutwell
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