Digital BW, The Print

In a message dated 9/3/08 1:38:27 PM, avr@... writes:
> 
> >In Photoshop you can create a true grayscale image which drops all RGB
> channels and has only a 'gray' (luminance?) channel.
> 
Right, or you can use various other methods to create either a neutral or a 
tinted/crosstinted image in Photoshop which still has RGB channels. Depends on 
your goals and your preferences...

> > In Lightroom, you
> can create a grayscale image, but it appears to retain the RGB
> channels.
> 
Keep in mind that Lightroom is keeping your RGB Raw file intact, so leaving 
your file in RGB is a given... its just a matter of how you "filter" that RAW 
file.

> > Other techniques also use the RGB channels as filters to
> create a BW image (Lots of controls in the color channels).
> 
Again, various techniques may generate a one channel, a three channel 
neutral, or a three channel non-neutral result. A three channel neutral file can be 
changed to a one channel neutral file will no loss (as the three channels are 
redundant, if truely neutral) and a one channel neutral file (it can't be 
anything BUT neutral if its one channel) can be converted to a three channel 
neutral file to get you back to the exact same file you started with. The three 
channel file has the advantages of printing more easily through some methods 
(Canon high bit export modules only took RGB files last time I checked, for 
instance) and can be tinted if desired. Or it can be "counter-tinted" to attempt to 
be get a neutral print if a true neutral doesn't print gray on a given 
printer... though thats a tricky situation.
> 
> The question is: For =good= BW printwork,
> 
There are lots of methods for good B&W prints...

>  should the final image sent
> to the printer be a TRUE, single-channel grayscale image, with no RGB
> info?
> 
This only matters in terms of the file types your chosen print system can 
handle, as long as you are talking literal grayscale images. As soon as I get 
perfectly neutral gray, I start looking at how I can make it a bit more rich 
(which also means not exactly neutral), and that requires either a change of ink 
formulations, a change of ink laydown methods (say via a profile), or a change 
of file channels...

>  I like working in Lightroom, but I would need to take the image
> to PS to make it a singe-channel true (by my def) grayscale image. Is
> this worth doing? Or will the printer/QTR figure it out?
> 
Lightroom RAW images are "unrendered" files. The general tendency of the day 
is to do more and more to these "preconversion" files, even, in some cases, 
printing from them. I suppose, for a rough print maybe. To me thats still a bit 
like washing the dinner dishes before I eat dinner. There are still MANY 
things I want to do to a good image in Photoshop before I'd ever consider printing 
it. It would be skipping dinner AND desert to me to go directly from 
Lightroom, to print. And even if I eventually decide to use Lightroom as my printing 
application (and its not ready yet, there are, for instance, only two rendering 
intents available, and that DOES NOT include my preferred intent) it will be 
the rendered TIFFs or Photoshop files I would be printing from Lightroom for my 
serious work, not the RAW files. I've spent a many years of my life learning 
how to improve images in Photoshop, and a few quick fix tools in Lightroom is 
not going to replace that overnight... not even for B&W files, which are 
simpler to process than color ones.
> 
> I'm setting up a Epson 1400/QTR/Piezo printer, and they indicate you
> should only print grayscale. So I'm looking for clear definition of
> grayscale.
> 
For me this would not be an issue, as I would be processing the images in 
Photoshop, and saving out as needed anyways. But its not an issue for me for 
other reasons: I print my color, my tinted B&W, and my neutral B&W all through 
Spyder3Print profiles to the same printers and inksets, and don't keep specialty 
B&W inksets running any longer. Not true of many on this list, however.

C. David Tobie
WW Product Technology Manager
Digital Imaging & Home Theater
Datacolor
CDTobie@...
www.datacolor.com/Spyder3
> 


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