Trouble with Custom QTR curve
2016-04-08 by Per Stavnesli
Based on a EB 6 v.1.1 profile for Epson Hot Press bright of which Paul Roark created for Epson 3880, I finally made a profile that gives a gradient scale and "bull eye" that is completely smooth.
My first test without modifications gave "Bulls eye" with distinct rings. I use Keith Cooper bw test file.
Ink pattern page by 100% clearly shows mottling at 50 for the grays(c,m,lc,lm,y) and K 50 is somewhat brighter than K 45. The remaining grays have also artifacts on 35. After some tests I have set ink limit K : 47 and grays : 32. I use Spyder print and take the average of four measurements. Crossovers set as described in calibration.pdf.
Has focused on creating a smooth as possible raw curve. This required Highlight: 6, Shadow: 20 and Gamma 1.05. As in the original profile I use Y as a curve. Print is much better than what I've ever produced in my darkroom.
In my case finding the “best” ink limit and making a smooth raw curve, solved the problem with uneven “bulls eye”.
CURVE_NAME=3880_HP_B_2880_versjon_2_ycurve
GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=47
BOOST_K=90
LIMIT_K=47
LIMIT_C=32
LIMIT_M=32
LIMIT_Y=16
LIMIT_LC=32
LIMIT_LM=32
LIMIT_LK=
LIMIT_LLK=
N_OF_GRAY_PARTS=5
GRAY_INK_1=K
GRAY_VAL_1=100
GRAY_INK_2=C
GRAY_VAL_2=31,75
GRAY_INK_3=M
GRAY_VAL_3=24,62
GRAY_INK_4=LC
GRAY_VAL_4=11,15
GRAY_INK_5=LM
GRAY_VAL_5=7,32
GRAY_HIGHLIGHT=6
GRAY_SHADOW=20
GRAY_OVERLAP=
GRAY_GAMMA=1,05
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=2
UNUSED_INK_1=LK
UNUSED_INK_2=LLK
CURVE_Y="0;0 5;2,25 10;5,35 20;14,7 30;24,3 40;36 50;48 60;60 65;65 70;67 80;52 90;27 100;0 """"
LINEARIZE="96,805 92,175 86,455 80,9775 75,72 69,8875 64,5975 60,4375 56,43 52,06 48,18 44,9825 41,805 37,715 34,895 32,1425 28,74 25,5375 22,4475 19,555 15,7125 "
Per Stavnesli
Norway