Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., workmantx@a... wrote:
> Jim,
> 
> I jumped into the game with PhotoShop 7, so I don't even have 
PhotoShop 6.  
> I've been using the MIS VM inks with Paul's curves and a 1280 and 
have 
> struggled at times with posterization.  I don't profess to be a PS 
wiz by any 
> stretch of the imagination.  By saying to use ver 6 for printing, I 
guess 
> you're saying that there's no easy way to get around the conversion 
space 
> issue for printing purposes??
> 
> Bob

No I'm sorry I wasn't clear on that. I guess I should preface by 
saying again that I think Paul origianlly matched those curves to 
1280/windows OS using photoshop 6.

First I'm going to explain it in many words so you can pick up 
everything. At the bottom I'll conclude with a simple 
statement/instruction that may help you use PS7 better with VM and 
1280/windows. So if you start getting confused skip to the end. But 
please be aware that the VM workflow can cause posterization because 
of many other things. This problem is perhaps at best only 1% of the 
issue. Okay?

Now each version, 5.5, 6, and 7 convert differently from greyscale to 
sRGB. It is a very small amount and the difference was verified with 
others who also run PS6 and PS7 both, on test files. Most everyone on 
this list who did the experiment agreed that the conversion "errors" 
were very very small (expressed as numerical histogram statistics 
variation from PS6 to PS7). Some people ran prints converted using 
both PS6 and PS7, then comparing them- but noone but me found a VISUAL 
difference. So the issue was put on a back burner. I found some 
posterization in around 90%k tones when using PS7 on one print file.

Then someone discovered that if AdobeRGB is used instead of sRGB for 
the destination conversion space, PS6 and PS7 convert the file 
mathmatically identically, or just about so. Unfortunately, Paul had 
chosen sRGB space somewhat by default, and never updated the 
1280/windows combo...so at the MIS site, in the table, sRGB space is 
still called out for the 1280/windows. If you had a Mac and an 1280, 
you would be okay, as Paul has done the curves assuming Adobe98 space. 
Or an 1290 and windows, etc.

So the story is this: You should try using Adobe98 instead of sRGB 
when you convert from greyscale to RGB. In the color setup you will 
see that PS7 has a pull down setting "photoshop 5 defaults" that Paul 
has specified be used to put PS in when converting to RGB. If you look 
down the dialouge box, you will see "greyscale 2.2" as the greyscale 
space. This is good; leave it. In the RGB section you see "sRGB". Just 
change it to "Adobe98". Then try some images. When I did and printed 
in both PS6 and PS7 with Adobe98, the prints were almost identical, 
except that I got some strange microbanding that I still haven't 
tracked down yet in the PS7 print. Also, the tonal range shifted, like 
increasing (decreasing?)lower midrange brightness very slightly. But 
99% of the posterization problem went away by simply using Adobe98 
space. However the prints varied in tone, since thay were converted in 
another space, you may or may not find it acceptable. If the tone on a 
step wedge is even enough for you even with the tonal shift in the new 
color space then just do all of your pix this way and calibrate your 
monitor to it, it may work. Print a step wedge and see how even it is.

But to keep my tones constant, and to avoid dealing with the banding 
issue that may or may not just be a red herring, I just opted out and 
use PS6 for printing. It's simpler for me. I could have lived with PS7 
and Adobe98 space, but you see I didn't have to- I HAD PS6.

So: Just use "Adobe98" instead of sRGB for the RGB color space when 
converting from greyscale to RGB. Simple.

But at least you have an idea of the history/compromises behind the 
issue now.

I'll repeat that if you're having posterization problems it could be 
due to about a dozen different things (and probably not the sRGB space 
snafu), from bad nozzles to bad/mislabelled/old ink, to the effect 
that Paul's curve has on the file (unfortunately, it puts gaps in the 
histogram, ie, you posterize the file to get it printed. Sometimes it 
does, somertimes doesn't effect final print.) It can be very 
frustrating. Hang in there, do searches on this forum for 
"posterization" or similar- lots of good info here. It will take time 
to get up to speed, so don't dispair of PS/VM yet.
yada, yada...
Jim H.