Digital BW, The Print

On Saturday, Dec 11, 2004, at 17:38 US/Pacific, 
DigitalBlackandWhiteThePrint@yahoogroups.com wrote:

> Message: 7
>    Date: Sat, 11 Dec 2004 12:52:49 -0000
>    From: "Steve Kale" <stevekale@...>
> Subject: Re: Re: LAB Step Wedge -- a grayscape Lab space
>
>
> Bruce
>
> I am sorry.  I shouldn't have blown you off so fast.  I also should 
> have added a better
> explanation when I curtly replied to Roy's post by saying:
>
>> So the
>> existing QTR profiles should work just fine as long as the pixel 
>> values
>> don't change, hence Assign-Profile.
>
> This would work if the print space was LAB but it isn't.
>
>
>
> Here is a fuller explanation and also, in effect, a summary of the 
> other thread.  To explain
> things more easily, go to this page and download the one page pdf file:
>
> http://homepage.mac.com/stevekale/stevekale2/FileSharing37.html
>
> It saves me having to put a bunch of numbers in this post and also 
> allows you to look at a
> couple of charts which will help.
>
> A RIP like QTR is, in effect, a set of look up tables which tell the 
> printer how much of each
> ink to put down ...
>
>
> You can simulate this pixel transformation in Photoshop using the 
> Curves function.  Bring
> up a 21 step wedge (or any other file), make sure it is tagged as LAB 
> (either by converting
> or assigning it doesn't matter for this exercise) and look at it.  Now 
> do a curves layer and
> input the co-ordinates that are listed for EEM - 8 bit input to 8 bit 
> equiv output.  You can
> actually cut to the chase and do just the beginning and end - it is a 
> straight line in the
> middle.  The two screen grabs at the bottom of the page show the 
> "curves" for each paper.
> NOW, with Preview checked you can see how your image will be printed 
> with QTR.  (Just
> don't print it with the curve in place else you will double the 
> transformation!)
>
>
>
> Secondly, and this finally answers your soft proof question, we get to 
> use Photoshop's
> built in Preview. When we have a transformation which alters pixel 
> values the effect is
> rendered on screen for us to see.  Thus by having all of the remapping 
> done to the image
> file (temporarily as a separate layer for printing only!!) in a layer 
> we can see the results of
> our work - real time soft proofing!
>
> So in my proposed methodology, I would in essence edit the image to my 
> liking on a well-
> calibrated monitor (this is reason enough to own a photospectrometer) 
> in a workspace
> that matches my print space.  Apply the "print curve" and check my 
> on-screen perfect
> preview of the image (except for ink hue) and maybe tweak the curve 
> for the specifics of
> the paper/ink tonal compression effects on this image, and then print. 
>  I would make sure
> that the "print curve" is saved as a layer because if I then decide to 
> print to glossy paper I
> don't need to compress the tonal range so much and hence I can use a 
> broader curve.
>
> I hope this helps
>
> Steve

Thank you Steve for the lengthly explanation. Ironically, this is 
exactly what I've been doing for previews with the difference that my 
QTR curves are set (by eye) for gamma 2.2 because I can't linearize 
without the densitomiter.

I have also experimented with applying my "s" helper curve directly to 
the QTR curve and building a new QTR curve with the "s" curve built in. 
I would think you could do this as well with a linearized curve as 
well. I suppose this kind of screws up the softproof accuracy though, 
but it is a good curve for printing from applications that are not 
photoshop.

It's been a fun and interesting discussion!

-bruce