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Using log density measurements with the Linearize command

Using log density measurements with the Linearize command

2017-07-20 by sanking@...

For some years I have been linearizing my digital negatives with an iOne spectrophotometer and the Linearize command. I invert the 21 step wedge file in the iOne folder, make a positive print in my process, then scan the step wedge to create a .txt file. I then drop the data from the .txt file on the QTR-Linearize data tool and, if all has gone well, get two sets of Linearize numbers, one for positive prints, a second for digital negatives. I enter the data for the digital negative and this has worked great for me.

What is the correct way to use log density measurements made with a reflection densitometer with the Linearize command. Should I enter the log density values in the Linearize line from low to high, or high to low? I have tried both ways but seem to be getting inconsistent results in that sometimes the resulting quad file looks like a quad file created with the iOne, at other times it appears that the curve is reversed.

Sandy

Re: Using log density measurements with the Linearize command

2017-07-20 by greg@...

A while back, Keith had helped me with doing this, maybe he will chime in but I remember him telling me that linearizing using density will cause the image to be darker vs linearization with LAB. I am not sure if this is what you are talking about. I usually ask you these questions. 

Greg

Re: [QuadtoneRIP] Using log density measurements with the Linearize command

2017-07-20 by Roy Harrington

Hi Sandy

The Linearize= command takes either L values or the log density values.
The goal is always linear L-values so densities are automatically converted.
It handles regular prints with the order white to black, and dig negatives
with the order black to white.
So for negs with density its like:
LINEARIZE="1.9 1.8 .... 0.2 0.1"

Roy

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On Wed, Jul 19, 2017 at 8:00 PM, sanking@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:


For some years I have been linearizing my digital negatives with an iOne spectrophotometer and the Linearize command. I invert the 21 step wedge file in the iOne folder, make a positive print in my process, then scan the step wedge to create a .txt file. I then drop the data from the .txt file on the QTR-Linearize data tool and, if all has gone well, get two sets of Linearize numbers, one for positive prints, a second for digital negatives. I enter the data for the digital negative and this has worked great for me.

What is the correct way to use log density measurements made with a reflection densitometer with the Linearize command. Should I enter the log density values in the Linearize line from low to high, or high to low? I have tried both ways but seem to be getting inconsistent results in that sometimes the resulting quad file looks like a quad file created with the iOne, at other times it appears that the curve is reversed.

Sandy




--
Roy Harrington
roy@...
www.harrington.com

Re: [QuadtoneRIP] Using log density measurements with the Linearize command

2017-07-24 by sanking@...

Hi Roy,

My assumption was that the density numbers should be entered as you note and that a correction curve with density numbers starting with the high density log measurements should be similar to a correction curve with lab values, inverted.

But sometimes this does not happen. I am including the .txt files of two profiles, one linearized with a spectro, the other with log density entries. When I run Install the one with lab values creates a good .quad file, but the one with density readings does not. If the lowest density readings is 0.00 the .quad files that is created is a straight line, similar to the original file with no linearization. If I enter a low density reading of 0.01, the .quad file is not created at all?

I have double checked my readings and entries and they look OK. Would appreciate your advice as to what I might be doing wrong.

Sandy

1. Linearize with lab values.

#PRINTER=Quad4880
#CURVE_NAME= Carbon100-230 #Based on Carbon Tissue #230, 14 grams of Black Cat Ink + 2 grams of Mixol #11, with tissue coated to a wet height of 0.9mm.
#Profile when printing a step wedge gives a DR (density range) of approximately log 2.05.
#With Tissue #230 sensitize with a 4% potassium dichromate solution, diluted 1+1 with acetone, approximately 10 ml per 8X10 sheet, applied in two coatings with a roller. 350 ULF units.

GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=100
LIMIT_K=25
LIMIT_C=1
LIMIT_M=1
LIMIT_Y=25
LIMIT_LC=1
LIMIT_LM=1
LIMIT_LK=50
LIMIT_LLK=1

GRAY_HIGHLIGHT=4
GRAY_SHADOW=4
GRAY_GAMMA= 1

CURVE_K= "0;0 100;100"
COPY_CURVE_C=K
COPY_CURVE_M=K
COPY_CURVE_Y=K
COPY_CURVE_LC=K
COPY_CURVE_LM=K
COPY_CURVE_LK=K
COPY_CURVE_LLK=K

LINEARIZE="25.36 30.5 34.58 37.29 40.37 43.36 45.96 48.44 50.99 53.52 56.41 59.24 61.36 64.34 67.25 69.62 72.48 76.31 83.55 89.9 96.74"

#LINEARIZE=“1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .00”

2. Linearize with log density readings.

#PRINTER=Quad4880
#CURVE_NAME= Carbon100-230 #Based on Carbon Tissue #230, 14 grams of Black Cat Ink + 2 grams of Mixol #11, with tissue coated to a wet height of 0.9mm.
#Profile when printing a step wedge gives a DR (density range) of approximately log 2.05.
#With Tissue #230 sensitize with a 4% potassium dichromate solution, diluted 1+1 with acetone, approximately 10 ml per 8X10 sheet, applied in two coatings with a roller. 350 ULF units.

GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=100
LIMIT_K=25
LIMIT_C=1
LIMIT_M=1
LIMIT_Y=25
LIMIT_LC=1
LIMIT_LM=1
LIMIT_LK=50
LIMIT_LLK=1

GRAY_HIGHLIGHT=4
GRAY_SHADOW=4
GRAY_GAMMA= 1

CURVE_K= "0;0 100;100"
COPY_CURVE_C=K
COPY_CURVE_M=K
COPY_CURVE_Y=K
COPY_CURVE_LC=K
COPY_CURVE_LM=K
COPY_CURVE_LK=K
COPY_CURVE_LLK=K

#LINEARIZE="25.36 30.5 34.58 37.29 40.37 43.36 45.96 48.44 50.99 53.52 56.41 59.24 61.36 64.34 67.25 69.62 72.48 76.31 83.55 89.9 96.74"

LINEARIZE=“1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .07 .00”

Re: [QuadtoneRIP] Using log density measurements with the Linearize command

2017-07-25 by Roy Harrington

Hi Sandy

Well that was a weird one. I tried the numbers you have and they worked just fine, but when
put all together they didn't work. After staring at it a while I suddenly saw it.

The double quotes on the density line are not regular double quotes. They are "smart" quotes or
maybe better described as dumb ones. If you just retype both it works just fine. Very, very subtle.

Old way:
LINEARIZE=“1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .07 .00”

Fixed way:
LINEARIZE="1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .07 .00"

BTW -- I also notice in the 2 files one is missing the .07 value. ?? See:
#LINEARIZE=“1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .00”

One comment: if you have a device that gives the L-values they in general will be more accurate.
Notice that all the L-values have 4 significant digit, whereas the densities barely have 2 digits
at the white end. Of course if you read density and convert to L you'll not really be any better.

Best,
Roy

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On Mon, Jul 24, 2017 at 4:14 PM, sanking@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:


Hi Roy,

My assumption was that the density numbers should be entered as you note and that a correction curve with density numbers starting with the high density log measurements should be similar to a correction curve with lab values, inverted.

But sometimes this does not happen. I am including the .txt files of two profiles, one linearized with a spectro, the other with log density entries. When I run Install the one with lab values creates a good .quad file, but the one with density readings does not. If the lowest density readings is 0.00 the .quad files that is created is a straight line, similar to the original file with no linearization. If I enter a low density reading of 0.01, the .quad file is not created at all?

I have double checked my readings and entries and they look OK. Would appreciate your advice as to what I might be doing wrong.

Sandy

1. Linearize with lab values.

#PRINTER=Quad4880
#CURVE_NAME= Carbon100-230 #Based on Carbon Tissue #230, 14 grams of Black Cat Ink + 2 grams of Mixol #11, with tissue coated to a wet height of 0.9mm.
#Profile when printing a step wedge gives a DR (density range) of approximately log 2.05.
#With Tissue #230 sensitize with a 4% potassium dichromate solution, diluted 1+1 with acetone, approximately 10 ml per 8X10 sheet, applied in two coatings with a roller. 350 ULF units.

GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=100
LIMIT_K=25
LIMIT_C=1
LIMIT_M=1
LIMIT_Y=25
LIMIT_LC=1
LIMIT_LM=1
LIMIT_LK=50
LIMIT_LLK=1

GRAY_HIGHLIGHT=4
GRAY_SHADOW=4
GRAY_GAMMA= 1

CURVE_K= "0;0 100;100"
COPY_CURVE_C=K
COPY_CURVE_M=K
COPY_CURVE_Y=K
COPY_CURVE_LC=K
COPY_CURVE_LM=K
COPY_CURVE_LK=K
COPY_CURVE_LLK=K

LINEARIZE="25.36 30.5 34.58 37.29 40.37 43.36 45.96 48.44 50.99 53.52 56.41 59.24 61.36 64.34 67.25 69.62 72.48 76.31 83.55 89.9 96.74"

#LINEARIZE=“1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .00”

2. Linearize with log density readings.

#PRINTER=Quad4880
#CURVE_NAME= Carbon100-230 #Based on Carbon Tissue #230, 14 grams of Black Cat Ink + 2 grams of Mixol #11, with tissue coated to a wet height of 0.9mm.
#Profile when printing a step wedge gives a DR (density range) of approximately log 2.05.
#With Tissue #230 sensitize with a 4% potassium dichromate solution, diluted 1+1 with acetone, approximately 10 ml per 8X10 sheet, applied in two coatings with a roller. 350 ULF units.

GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=100
LIMIT_K=25
LIMIT_C=1
LIMIT_M=1
LIMIT_Y=25
LIMIT_LC=1
LIMIT_LM=1
LIMIT_LK=50
LIMIT_LLK=1

GRAY_HIGHLIGHT=4
GRAY_SHADOW=4
GRAY_GAMMA= 1

CURVE_K= "0;0 100;100"
COPY_CURVE_C=K
COPY_CURVE_M=K
COPY_CURVE_Y=K
COPY_CURVE_LC=K
COPY_CURVE_LM=K
COPY_CURVE_LK=K
COPY_CURVE_LLK=K

#LINEARIZE="25.36 30.5 34.58 37.29 40.37 43.36 45.96 48.44 50.99 53.52 56.41 59.24 61.36 64.34 67.25 69.62 72.48 76.31 83.55 89.9 96.74"

LINEARIZE=“1.37 1.21 1.09 1.02 .95 .87 .82 .77 .72 .65 .60 .55 .50 .45 .41 .37 .33 .27 .16 .07 .00”




--
Roy Harrington
roy@harrington.com
www.harrington.com

Re: [QuadtoneRIP] Using log density measurements with the Linearize command

2017-07-25 by sanking@...

Hi Roy,

Thanks very much for looking at the profiles and finding the problem. I can not figure out how I got the quotes wrong since I usually just copy and paste the Linearize command with the quotes from existing profiles that are known to work.

I realize that the lab values are more accurate and use them in my own work, but very few of my carbon transfer students own spectrophotometers so I try to explain alternative ways to linearize profiles with different devices, which includes densitometers and scanners.

Sandy

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