QTR-Quadtone RIP

(Ping: Paul Roark)

I decided to create a profile for HanPhotoRag for my R2400 using K7 inks; Mac OS 10.5.5 
Leopard, QTR 2.6.  Although results with the canned QTR profile look pretty good, perhaps 
they can be better.

I scanned a Kodak gray card, along with the 21-step scale, as described by Paul.  With 
Levels, I made the gray card 50% which, of course shifted the values of the 21-step scale.

Step 21 reads 100% (black).  Step 1 reads 0 (paper white).

Unfortunately, steps 4, 3, and 2 also read 0, i.e., there is a flat spot.  And in Paul's pdf, he 
notes that one should be able to create an ICC - provided there is no flat spot.  When I 
plod on, dropping the txt file into Create ICC (both on the desktop) I get the message: 
"The Lab values are not in order.  Cannot make a profile."  If I reverse the order, I get the 
same message but with a different empty table.

I may also be confused about the proper order; Paul refers to the high numbers as being 
at the light end (white = 100%), whereas step 21 in the 21-step strip is black, 100%.

So, now I'm stuck.  Assuming that the flat spot is the problem, what is the next step? (And 
why do I have such a large flat spot?)  Or, perhaps I've not followed Paul's instructions 
properly.

Advice much appreciated.

Harry

Hi Harry,

>I decided to create a profile for HanPhotoRag for my R2400 
> using K7 inks; ... results with the canned QTR profile look 
> pretty good, perhaps they can be better.

>... steps 4, 3, and 2 also read 0, i.e., there is a flat spot.

If the flat spot was on the 21-step test print, then the profile you're
using is not good enough for the system to work.

If the test strip looks OK, but the scanned image is the problem the scanner
needs to have its controls adjusted.  You can't have the scanner clipping
the ends of the test strip.

Paul
www.PaulRoark.com

Thanks, Paul.  I kinda came to the same conclusion.  The test strip looks
good; I can certainly see the different shades at 4, 3, and 2.  So it has to
be the scanner (Epson Perfection 3590.)  I¹ll see if there anything that can
be done with the controls.  Will report back if successful.

Harry


On 11/27/08 2:35 AM, "Paul Roark" <paul.roark@...> wrote:

>  
>  
> 
> Hi Harry,
> 
>> >I decided to create a profile for HanPhotoRag for my R2400
>> > using K7 inks; ... results with the canned QTR profile look
>> > pretty good, perhaps they can be better.
> 
>> >... steps 4, 3, and 2 also read 0, i.e., there is a flat spot.
> 
> If the flat spot was on the 21-step test print, then the profile you're
> using is not good enough for the system to work.
> 
> If the test strip looks OK, but the scanned image is the problem the scanner
> needs to have its controls adjusted.  You can't have the scanner clipping
> the ends of the test strip.
> 
> Paul
> www.PaulRoark.com

-- 

Harry F. Lockwood




[Non-text portions of this message have been removed]

>... The test strip looks good; I can certainly see the different 
> shades at 4, 3, and 2. 

>So it has to be the scanner (Epson Perfection 3590.) I¹ll 
> see if there anything that can be done with the controls. 

Using just the gray card to adjust the gamma of a scan was a simplification
of using a Kodak Q13 card to do a more serious scanner calibration.  See
pages 3-4 of http://www.paulroark.com/BW-Info/Making_B-W_ICCs-1.pdf   I
found that most scanners can produce reasonably linear grayscale scans if
the gamma is corrected, but if yours can't it becomes much more work.  Your
scanner may have also come with some system to calibrate it. 

Paul
www.PaulRoark.com

I use the Q13 method Paul describes with my Epson 4990. This does 
work although it takes some fiddling to find the correct settings. 
Make sure you use black papper behind the Q13 and the test strips 
when you scan them, it does make a difference in the flare (contrast) 
of the image.

--- In QuadtoneRIP@yahoogroups.com, "Paul Roark" <paul.roark@...> 
wrote:
>
> >... The test strip looks good; I can certainly see the different 
> > shades at 4, 3, and 2. 
> 
> >So it has to be the scanner (Epson Perfection 3590.) I¹ll 
> > see if there anything that can be done with the controls. 
> 
> Using just the gray card to adjust the gamma of a scan was a 
simplification
> of using a Kodak Q13 card to do a more serious scanner 
calibration.  See
> pages 3-4 of http://www.paulroark.com/BW-Info/Making_B-W_ICCs-
1.pdf   I
> found that most scanners can produce reasonably linear grayscale 
scans if
> the gamma is corrected, but if yours can't it becomes much more 
work.  Your

> scanner may have also come with some system to calibrate it. 
> 
> Paul
> www.PaulRoark.com
>