Digital BW, The Print

Hi Olivier,

This is very helpful.  
From what I see you are very close to the right result.

First issue is comma vs point in numbers.  The Lab values that you entered into
the pseudo data file have commas instead of points.  I think this is what is
causing the little wiggles in the curve -- the numbers are being truncated.  I can
fix this in the next version.

I've taken your values and they make a reasonable icc profile.  Both Steve and
I are on Macs so the program that plots the icc's is different.  From your
description I think your program swaps the x and y axis so what's curves down
for you is curved up for us.  The other difference is that icc's can have two
different PCS's XYZ or Lab.  Either can be used but the curves are very different.
The Gray Matte Paper one is probably based on XYZ and the one you created
is Lab which makes them hard to compare.  (I've made both kinds the Lab ones
are more obvious to look at since they start straight.)

I think you have a decent icc file as it is (except for the wiggles).  Your data
shows a darker stepwedge as expected.  No doubt you've plotted the two sets
of Lab data (G2.2 and G2.2profile).   The difference shouldn't look like a gamma
curve, in fact it'll look at lot like the icc xTRC curve I think you are seeing.  This
is basically the Perceptual Intent mapping.  It's a straightline expansion in Y units
but viewed in Lab units it darkens all and bunches the blacks together somewhat.
(BTW, notice that the K=50 step reads L=54 which is exactly the right for GG2.2)

As you mentioned the black end gets pretty blocked up.  This is due also to the
fact that you are using GG2.2.  This alone has fairly blocked shadows (see the
reduced separation on your screen) and when force that onto matte paper you 
get hit again.   But the idea is to match the print with the screen so this ought
to give you as close a match as possible.

I think you are to the point where you should try a real picture, edited in PS
to what you want on the screen (embedded profile doesn't matter).  Convert to
the GrayICC that you made and print with QTRgui.  See how well the print
matches the screen.

Roy


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "odesmais" <odesmais@y...> 
wrote:
> Roy, Steve,
> 
> Thanks both of you for your help. I agree this shoud go more 
> practical. So my system :
> 
> Windows XP
> Epson 1280
> PiezoBW ICC CIS (K, Dark grey, 2 same grey, 2 same light grey, the 
> tubing and correspondances KCMY/LC/LM with the Piezo inks have of 
> course been re-checked)
> DTP 20 X-rite Spectro
> Colorshop X for color/gamut/profile/measures viewing
> Paper : EEM 
> 
> The curve is :
> 
> PRINTER=Quad1290
> CURVE_NAME=EEM2
> GRAPH_CURVE=YES
> N_OF_INKS=6
> DEFAULT_INK_LIMIT=65
> BOOST_K=75
> LIMIT_K=
> LIMIT_C=
> LIMIT_M=50
> LIMIT_Y=50
> LIMIT_LC=
> LIMIT_LM=
> N_OF_GRAY_PARTS=4
> GRAY_INK_1=K
> GRAY_VAL_1=100
> GRAY_INK_2=C
> GRAY_VAL_2=39
> GRAY_INK_3=M
> GRAY_VAL_3=12
> GRAY_INK_4=Y
> GRAY_VAL_4=5
> GRAY_HIGHLIGHT=4
> GRAY_SHADOW=8
> GRAY_OVERLAP=5
> 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_LC=M
> COPY_CURVE_LM=Y
> LINEARIZE="96,37 81,17 70,98 62,61 54,44 48,72 45,2 41,69 38,03 34,46 
> 32,23 30,35 29,03 27,75 25,28 22,65 20,87 19,72 18,61 18,08 17,75 "
> 
> L* measures once linearised :
> 
> L A B
> 96,45 -0,20 -1,20
> 92,90 -0,06 0,03
> 89,24 0,12 1,26
> 85,27 0,31 2,21
> 81,34 0,56 3,00
> 77,40 0,68 3,63
> 73,61 0,76 4,15
> 70,04 0,84 4,32
> 66,63 1,01 4,34
> 62,30 1,13 4,52
> 58,03 1,25 4,48
> 53,54 1,42 4,28
> 50,04 1,39 4,27
> 45,97 1,44 3,81
> 41,94 1,35 3,41
> 37,92 1,29 3,10
> 34,08 1,02 2,91
> 30,44 0,86 2,10
> 25,85 0,78 1,77
> 21,73 0,85 1,67
> 17,70 0,73 1,24
> 
> PM5 file I feed Create-ICC with :
> 
> LGOROWLENGTH 1
> CREATED "7/21/2003" # Time: 12:57
> INSTRUMENTATION "eye-one"
> MEASUREMENT_SOURCE ""Illumination=D50 ObserverAngle=2°
> WhiteBase=Absolute Filter=No""
> KEYWORD "SampleID"
> KEYWORD "SAMPLE_NAME"
> NUMBER_OF_FIELDS 9
> BEGIN_DATA_FORMAT
> SampleID SAMPLE_NAME GRAY XYZ_X XYZ_Y XYZ_Z
> LAB_L LAB_A LAB_B
> END_DATA_FORMAT
> NUMBER_OF_SETS 21
> BEGIN_DATA
> 1 A1 0.00 90.30 93.00 83.24 96,45 -0,20 -1,20
> 2 B1 5.00 81.48 83.75 73.66 92,90 -0,06 0,03
> 3 C1 10.00 72.64 74.52 64.14 89,24 0,12 1,26
> 4 D1 15.00 64.02 65.53 55.03 85,27 0,31 2,21
> 5 E1 20.00 56.26 57.46 47.10 81,34 0,56 3,00
> 6 F1 25.00 50.08 51.05 41.01 77,40 0,68 3,63
> 7 G1 30.00 43.86 44.60 34.99 73,61 0,76 4,15
> 8 H1 35.00 37.74 38.29 29.29 70,04 0,84 4,32
> 9 I1 40.00 32.45 32.85 24.73 66,63 1,01 4,34
> 10 J1 45.00 27.61 27.90 20.62 62,30 1,13 4,52
> 11 K1 50.00 23.84 24.05 17.57 58,03 1,25 4,48
> 12 L1 55.00 20.16 20.31 14.71 53,54 1,42 4,28
> 13 M1 60.00 16.91 17.04 12.35 50,04 1,39 4,27
> 14 N1 65.00 13.62 13.72 9.98 45,97 1,44 3,81
> 15 O1 70.00 11.01 11.10 8.10 41,94 1,35 3,41
> 16 P1 75.00 8.96 9.04 6.59 37,92 1,29 3,10
> 17 Q1 80.00 7.10 7.16 5.22 34,08 1,02 2,91
> 18 R1 85.00 5.56 5.61 4.11 30,44 0,86 2,10
> 19 S1 90.00 4.32 4.36 3.18 25,85 0,78 1,77
> 20 T1 95.00 2.92 2.95 2.21 21,73 0,85 1,67
> 21 U1 100.00 2.04 2.08 1.56 17,70 0,73 1,24
> END_DATA
> 
> As you can see only the Lab (not the xyz, just a bit lazy to do the 
> copy/paste manipulation also for xyz but it does not seem to be 
> necessary)have been modified from a file I found (BTW on one of the 
> groups).
> 
> Now L* measures :
> 
> - G2,2 is the QTR stepwedge opened in PS converted to grey working 
> space gamma2,2 (all values read from 0-100 in 5 even steps)and 
> printed on EEM.
> - G2,2 is QTR stepwedge opened in PS converted to grey working space 
> gamma2,2 and converted again with the QTR ICC created (values from 0-
> 100 is various steps after the QTR conversion as expected)and printed 
> on EEM. 
> 
> G 2,2	G 2,2_Profil
> 
> 96,16	96,31
> 92,75	92,82
> 88,97	87,89
> 84,98	83,7
> 81,03	79,67
> 76,85	75,25
> 72,72	70,42
> 69,22	66,39
> 65,85	62,03
> 61,83	57,92
> 57,86	54,21
> 54,04	49,45
> 50,62	46,73
> 46,93	41,67
> 42,84	36,07
> 38,59	30,65
> 34,4	26,86
> 30,44	23,35
> 25,46	19,83
> 21,31	18,43
> 17,93	17,5
> 
> My problem is :
> 1. I expected the compression resulting of the conversion should be 
> in the form of a "perfect" curve but if you draw the G2.2profiled L* 
> curve (excel)you will see "bumpings" (I guess this is the way you say 
> it in English). G2,2 is a straight line, while G2,2_Profil is neither 
> a straight line (fine) nor a perfect curve in a kind of gamma shape 
> one.
> 2. Why the Generic Matte Profile and the QTR ICC created one don't 
> have the kTRC curve in the same part of the 45° line (GMprofile 
> above, mine below?).In IMHO both should be in the upper part 
> (lighter) because if Lblack is no pure black the all values should be 
> lighten "perceptual". Besides GMprofile kTRC is a perfect curve again 
> in a fine gamma shape look, while the one I get is an bumped bowl 
> shape (what my 3-years-old daughter would draw as a smile !!!). It 
> doesn't matter really nut this is where I feel it demonstrate a 
> problem.
> 3. I get significant blockages in the 90-100 once the profile is 
> applied so that I did not even bother running the Piezo test for the 
> lightest 10-5% and darkest 90-95%.
> 
> At the time I'm writting it I'm just getting a bad doubt : should the 
> PM5 file first be feeding the "QTR-Linearize-data" and the after get 
> the "whatever-out.txt" dropped to "QTR-create-ICC" ? 
> 
> I'm FOR SURE doing something wrong but can't identify... 
> 
> I can e-mail my profile or whatever is needed if necessary.
> Sorry for my wording, it's not too easy to express these things.
> Thanks again.
> 
> Olivier