Digital BW, The Print

Well it depends.  (Personally I don't use the Channel Mixer method as I find
it restricting.  I prefer to use the Split Channels method and consequently
I get a greyscale file.  I use GG 2.2 because I can bounce into Adobe RGB
for PK Sharpener and back to greyscale without vexing the file too much.  I
do not store this output sharpened file and so my B&W image is stored in
greyscale with its lower storage and work size.  I do not print using Paul's
curves.)  It depends on your workflow (as Clayton said in an earlier mail).
If the rest of your workflow is expecting a gamma of 2.2 and you use a
colour space with a different gamma then you will run into problems if you
are not colour managing your output to the printer (ie selecting a printer
profile with Let Photoshop Determine Colors at the printing stage): in this
case your selection of workspace matters.  I believe Paul does all his
curves work for an Adobe RGB space and hence working in ProPhoto is not a
good idea if you want to use his methodology.  Clayton uses DotGain 20%
because he too doesn't colour manage his output and he finds that this
workspace matches his print space the best.  My bet is that a workspace of
GG2.2 or Adobe RGB is the underlying assumption in the non colour managed
Epson Adv B&W workflow.

BUT the core point of this conversation has been that a No Color
Management/Same as Source workflow is now rather dated (perhaps with the key
exception of Paul's workflow - see below *).  Anyone printing to a
linearised greyscale, such as those using QTR, IJC/OPM and Epson Adv B&W, or
those printing to a non-linearised greyscale, such as those using Black Only
printing, would do well to avail themselves of the little but powerful
module included with QTR called QTR Create ICC.  This module allows you to
profile the luminance of your printer's greyscale production and store it as
an ICC profile.  So when you come to print you can Let Photoshop Determine
Colors and convert the image file from whatever colour space you are using
for the file or workspace to a printer/output space that reflects your, well
err, printer output.  In this case it doesn't matter whether you have a
greyscale image tagged as GG2.2, GG1.8, DG20%, Adobe RGB, ProPhoto RGB or
any other.  When it leaves Photoshop it will be converted to a profile which
reflects your printer setup.  This is just like a colour (colour managed)
workflow.  The one difference is that it makes no attempt to output manage
hue - your greyscale hue is determined by the RIP or driver and ink/paper
setup you use to generate it.  In other words, there is no attempt to
maintain your nice neutral image on screen as neutral in the printer if you
have, say, selected a warm QTR curve.  Only the luminance axis is managed
and the print comes out warm as you wanted.  While this is the case, Roy is
working on a way to allow you to soft proof hue with the same ICC profile.
So when you set up a soft proof in the normal fashion in Photoshop you will
see the hue of the profiled printer setup (eg QTR with a warm curve selected
or Epson Adv B&W set to warm and darker - whichever settings you profiled
with QTR Create ICC) and the impact of the luminance management (the
compression to the reduced dynamic range of the printer) - for example a
nice warm image as it would print (reduced dynamic range and all).  THIS IS
AN EXTREMELY POWERFUL TOOL AND WELL WORTH THE COST OF QTR ON ITS OWN.  Even
if you are not using QTR as your RIP/driver, if you have an Eye-One Photo
and hence can use MeasureTool to read a step wedge printed using whatever
workflow you use, then you can likely benefit from using QTR Create ICC
(especially if you have a lumpy non linear output like black only).

Steve


* I noted Paul's RGB curve workflow as a possible exception because I
haven't fully thought it through.  Paul, in essence, targets a particular
greyscale profile with his curves.  This is quite different from getting
what you get with, say, black only (by this I mean you aren't able to change
the luminance profile of the greyscale generated by your printer in black
only mode - it is a black box and you get what you get) or managing, through
linearisation, your greyscale output.  Paul's curves in effect define the
transformation from workspace to print space.  With the other methods the
print space is constructed independently of the workspace (with the minor
exception that Clayton hunted out a workspace which best matched the print
space - a good starting point).  QTR Create ICC was designed to use colour
theory to manage the transformation between two independent spaces.



> From: Howard Shaw <glassman@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Thu, 22 Sep 2005 08:08:56 +0100
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: Re: [Digital BW] Re: B/W on the 9600
> 
> 
> Steve Kale wrote:
>> ...   If you are using Channel Mixer to convert to B&W
>> and want to be able to retrace your steps then saving this step as a layer
>> will, I believe, require you to keep the document in RGB.  This isn't such a
>> big deal except for the extra size etc.  If you are not worried about
>> keeping this layer then I would flatten and then go to GG 2.2 greyscale.
>> You can then easily save the document then bounce to Adobe RGB (which has a
>> gamma of 2.2) for your Photokit output sharpen and then print - discarding
>> the output sharpened file once it has printed.
>> 
>> 
> What is the advantage of converting to GG2.2 if you're workflow requires
> you to convert back to RGB? The same applies when using Paul Roark's
> curves for example. Retaining the original colour file and being able to
> alter the channel mixer settings etc right up until print time surely
> outweighs any advantage in converting?
> 
> Howard
> 
> 
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