QTR-Quadtone RIP

Hi Howard,
yesterday night i used all your advices and finally i create a curve
that prints a 21step.psd without a step (may be just a little step but
nothing compere to the other curve). happy of the result i printed a
foto and i realized that was darker then what i was seeing on my
monitor. I modifyed gamma from 1 to 1,5 but the result was that the
picture was lighter but the step appeared again !!! 

The curve that works well but print darker is here :

N_OF_INKS=6
DEFAULT_INK_LIMIT=30
BOOST_K=30
LIMIT_K=30
LIMIT_C=15
LIMIT_M=15
LIMIT_Y=13,33
LIMIT_LC=13,33
LIMIT_LM=13,33
N_OF_GRAY_PARTS=3
GRAY_INK_1=K
GRAY_VAL_1=100
GRAY_INK_2=C
GRAY_VAL_2=33,33
GRAY_INK_3=LC
GRAY_VAL_3=16,66
GRAY_HIGHLIGHT=10
GRAY_SHADOW=6
GRAY_OVERLAP=20
GRAY_GAMMA=1
GRAY_CURVE=
N_OF_TONER_PARTS=0
TONER_HIGHLIGHT=10
TONER_SHADOW=10
TONER_GAMMA=1
TONER_CURVE=
N_OF_TONER_2_PARTS=0
TONER_2_HIGHLIGHT=10
TONER_2_SHADOW=10
TONER_2_GAMMA=1
TONER_2_CURVE=
N_OF_UNUSED=0
COPY_CURVE_M=C
COPY_CURVE_Y=LC
COPY_CURVE_LM=LC


do you think i have to preprocess the photos with a brigthness layer
on photoshop ? or may be i am a problem with settings of my monitor
(lcd samsung) ?


 

--- In QuadtoneRIP@yahoogroups.com, Howard Shaw <glassman@...> wrote:
>
> Hi Paolo
> 
>  > on K for limit 30 i have L=24
>  > on C and M for limit 90 i have L=35 ---> on K i have L=35 for
limit 15
>  > on Y,LC,LM for limit 90 i have L=45 ---> on K i have L=45 for
limit 10
>  >
>  > so i created a curve with
>  > C limit 45 (half of 90) and denisty = 15/30*100 = 50
>  > M copy corve from C
>  > LC limit 30 (90/3) and denisty = 10/30*100 = 33
>  > Y copy corve from LC
>  > LM  copy corve from LC
> 
> I'm not sure if I follow that although the end result might be okay! 
> It's not clear from what you have written but you should compare the 
> 100% patch for C printed at your chosen limit (90) with the
equivalent K 
> value on the reprinted ink separation page with the ink calibration bar 
> set at 30 (your chosen limit for K).
> 
> Then calculate as follows:
> The 100% patch for C on the limit 90 print measures L=35 which is 
> equivalent to the 50% K patch on the limit 30 print
> Therefore first partition = 50
> The 100% patch for LC on the limit 90 print measures L=45 = 33% K 
> 'patch' (ie somewhere between the 30% & 35% patches) on the 30%
limit print
> Therefore second partition = 33
> 
> You are correct with your sub-division of the duplicated inks.
> 
> As a general comment, the limits and densities for the non-K inks seem 
> high to me particularly for 2880dpi but I don't have an R260 so can't 
> judge. Are you sure you are getting clearly visible separation between 
> patches at 90%? If not, you should reduce the limits to a point where 
> you are getting good separation.
> 
> You are at a disadvantage using a scanner as opposed to a densitometer 
> or similar. For example the Dmax for eboni on EAM should be in the 
> region of 16-17, not 24.
> 
>  > why you choose :
>  > GRAY_HIGHLIGHT=4
>  > GRAY_SHADOW=8
>  > GRAY_OVERLAP=16
>  > GRAY_GAMMA=1
> 
> These are the defaults - no need to change them unless there is a 
> particular issue.
> 
>  > a last question : have i to print with 1440 dpi on EAM ?
> 
> No, 2880dpi is fine as long as the inks are limited correctly.
> 
> regards
> Howard
> 
> paolovertullo wrote:
> > Hi Howard
> > just to see if i have understood well
> > 
> > I scanned the ink_limit_pattern and misured the L value with photoshop
> > and found that 
> > 
> > on K for limit 30 i have L=24
> > on C and M for limit 90 i have L=35 ---> on K i have L=35 for limit 15
> > on Y,LC,LM for limit 90 i have L=45 ---> on K i have L=45 for limit 10
> > 
> > so i created a curve with 
> > C limit 45 (half of 90) and denisty = 15/30*100 = 50
> > M copy corve from C
> > LC limit 30 (90/3) and denisty = 10/30*100 = 33
> > Y copy corve from LC
> > LM  copy corve from LC
> > 
> > why you choose :  
> > GRAY_HIGHLIGHT=4
> > GRAY_SHADOW=8
> > GRAY_OVERLAP=16
> > GRAY_GAMMA=1
> > am i supposed to make some other considerations ? 
> > a good starting point wasn't 
> > GRAY_HIGHLIGHT=10
> > GRAY_SHADOW=10
> > GRAY_OVERLAP=
> > GRAY_GAMMA=1
> > 
> > Here my new .qidf i named the curve with your name :-)
> > 
> > PRINTER=QuadR260-MIS
> > CURVE_NAME=MK-EAM-HOWARD_1
> > GRAPH_CURVE=YES
> > N_OF_INKS=6
> > DEFAULT_INK_LIMIT=30
> > BOOST_K=35
> > LIMIT_K=30
> > LIMIT_C=45
> > LIMIT_M=45
> > LIMIT_Y=30
> > LIMIT_LC=30
> > LIMIT_LM=30
> > N_OF_GRAY_PARTS=3
> > GRAY_INK_1=K
> > GRAY_VAL_1=100
> > GRAY_INK_2=C
> > GRAY_VAL_2=50
> > GRAY_INK_3=LC
> > GRAY_VAL_3=33
> > GRAY_HIGHLIGHT=4
> > GRAY_SHADOW=8
> > GRAY_OVERLAP=16
> > GRAY_GAMMA=1
> > GRAY_CURVE=
> > N_OF_TONER_PARTS=0
> > TONER_HIGHLIGHT=10
> > TONER_SHADOW=10
> > TONER_GAMMA=1
> > TONER_CURVE=
> > N_OF_TONER_2_PARTS=0
> > TONER_2_HIGHLIGHT=10
> > TONER_2_SHADOW=10
> > TONER_2_GAMMA=1
> > TONER_2_CURVE=
> > N_OF_UNUSED=0
> > COPY_CURVE_M=C
> > COPY_CURVE_Y=LC
> > COPY_CURVE_LM=LC
> > 
> > a last question : have i to print with 1440 dpi on EAM ?
> > 
> > many many thanks
> > Paolo
> >
>