QTR-Quadtone RIP

Hi Everyone,

Trying to figure out the process of making a digital negative with QTR

I am looking at what was written in the past by Sandy and Mike about using a single gray system. I am using a Epson 7880 on a Mac and printing mostly Palladium prints. I am using florescent BLB bulbs in a UV box. I am using Fixxons and Hahnemuhle Platinum Rag. I am using 18 drops FO + 18 drops PD 2 drops Tween 20 and 1 drop Na2 2.5% I keep the paper overnight in a humidity chamber at 45% humidity at around 70-74 degrees. I coat it and let is set for 4-5 minutes. I don’t dry it with any fan after.

Step 1: I used a 31 step Tablet from Mark Nelson and figured that my max print time for blacks. 7 minutes gave me blacks merged from step 1-3. I made my printing time 4 minutes.

Step 2: I printed the inktone separation test in Quadtone RIP Calibration mode (per Clays instructions) I found the K ink becomes pure white at 80%. I compared the LK strip to the K strip and found that 85% LK = 50%K. Yellow is 80% pure white and the LLK 100% LLK = 25%K. Again following what Clay wrote a while back

Where I get confused now is that if I look at what Sandy and John wrote in the newly released and wonderful Carbon book, I don’t see how you get the limits of the inks. If I go by Clays method, I get:

DEFAULT_INK_LIMIT=100

BOOST_K=0

LIMIT_K=80

LIMIT_C=1

LIMIT_M=1

LIMIT_Y=12

LIMIT_LC=1

LIMIT_LM=1

LIMIT_LK=85

LIMIT_LLK=100

N_OF_GRAY_PARTS=3

GRAY_INK_1=K

GRAY_VAL_1=100

GRAY_INK_2=LK

GRAY_VAL_2=50

GRAY_INK_3=LLK

GRAY_VAL_3=20

When I look at Sandy’s I see

DEFAULT_INK_LIMIT=55

LIMIT_K=25

LIMIT_C=25

LIMIT_M=1

LIMIT_Y=25

LIMIT_LC=1

LIMIT_LM=1

LIMIT_LK=40

LIMIT_LLK=1

How do you get those values from the inktone separation test? Do you enter the info for density or is that replaced with the DEFAULT_INK_LIMIT=55

I tried printing out the profile like this:

GRAPH_CURVE=YES

N_OF_INKS=8

DEFAULT_INK_LIMIT=55

LIMIT_K=25

LIMIT_C=25

LIMIT_M=1

LIMIT_Y=25

LIMIT_LC=1

LIMIT_LM=1

LIMIT_LK=40

LIMIT_LLK=1

GRAY_HIGHLIGHT=4

GRAY_SHADOW=4

GRAY_GAMMA= 0.7

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

It installed but I got an error about the curve. When I printed it, the ink was dripping off the negative.

The other problem I had was when I tried to go to the next step of building the curve. I tried the Build QTR Curve.jsx with Photoshop CC 2017 and I got an error about a command no longer valid and the action stopped. I also have a Spider 4 spectrometer and was able to do it that way using the B&W mastery excel sheet.

I know, lots of questions, but I have done about 30 prints already trying to get this process down.

Thanks,

Greg

Greg,

Please look at the Files section of this forum. There, in the folder Docs, you will find a folder called QTR Files for Digital Negatives where I talk about two different methods of profiling that I use, one for an all gray ink set, the other for a single gray value system where I use the Epson OEM inks. I call that Carbon 100 because it is very easy and simple to explain to students. Like English 101 or French 101 in college!!

Basically, I only use three of the 8 inks in an Epson K3 ink set (PK, Y and LLK) because these are the only ones that block UV light. All of the others I set to defalt level of 1 so that the printer uses some of the ink to inks to keep the nozzles happy. The default level of the PK, Y and LLK is set relative to each other based on the UV blocking power of each. PK and Y are approximately equal so I set them at the same value, LLK needs about 2X the percentage of PK and Y to lay down the same UV blocking, so I set the default ink level to twice the percentage. In the Carbon 100 profile in the Files section I have these values set to PK=25, Y=25 and LLK=50, and in that profile you get UV blocking that gives a density range of about log 2.05 on OHP. If that DR turns out to be too high for your process you decrease the number of these three inks proportionally, say -10%, or -20%, etc. If these limits give a negative with a density range too low for your process you increase the number of these three inks by proportionally, for example by +10% or +20%.

Basically, you adjust the ink percentage of the PK, Y and LLK until you can print a step wedge negative (ising your standard printing time) that has a full range of tones from DMax to DMin. Then you can linearize the profile, your method with the Spyder 4 and Richard's spread sheet is a good way, or you can also just enter the log density numbers in the LINEARIZE command, as I do in the sample Carbon 100 profile in the Files section.

Sandy