QTR-Quadtone RIP

reating curve redcolour-2-3

## QuadToneRIP K,C,M,Y,LC,LM,LK,LLK

# QuadProfile Version 2.7.7.0

# K curve

0 0% |

11 4% |mk g

21 8% | mk g

32 13% | cmk g

43 17% | cm k g

53 21% | c m k g

64 25% | c m k g

74 29% | c m k g

85 33% | c m kg

96 38% | c m g k

106 42% |Y g m k

117 46% |Y g c m k

128 50% |Y g c m k

138 54% |YM g c m k

149 58% | Y g c m k

159 62% | Y g c m k

170 67% | Y g c m k

181 71% | Y g c m k

191 75% | Y g c m k

202 79% | Yg c m k

213 84% | Yg c m k

223 87% | YM c m k

234 92% | YK c m k

244 96% | Y cKm k

255 100% | Y M K

I own and use Richard's set of Tools for QTR and strongly recommend them as they are useful for both beginners and advanced users of QTR.

Let me remark first that I am a carbon transfer printer who has been using digital negatives for almost twenty years, and during that time I used image setter negatives and numerous inkjet printers and methods, including Burkholder, PDN and various other forms of colorized negatives with the Epson driver. Since 2007 I have used QTR for making digital negatives, in fact I learned QTR from Ron Reeder and have since continued on my own, and with the help of others. I recently published a new book on carbon transfer, The Carbon Print, that has a long chapter on negative making, including digital negatives, that covers both history and pratice. Even those who are not interested in carbon pritning might learn something from this chapter.

If you are looking for a very effective method of making digital negatives with QTR and the Epson OEM k3 inks please have a look at the files I have posted on this forum. Files>Docs>QTR Files for Digital Negatives. Ans specifically, look at the files Carbon 100.doc, and Carbon 100.txt. And testing would cost you nothing but a bit of time since you are already using QTR and an Epson printer with K3 inks. The newer Epson HDR inks also work well, though some adjustment would be required to reduce negative density since these inks are a bit more opaque than the K3 inks, i.e. they block more UV light.

I quote from the Carbon 100 doc file.

Carbon 100 is a QTR profile for printing digital negatives with an Epson K3 printer. This profile uses a single gray value where all curves follow the K. The profile uses the three inks in the K3 ink set that are effective UV blockers, PK, Y and LK. The LIMIT of these three inks has been set so that all three are approximately equal UV blockers, which serves to give a smoother look than when unequal UV blockers are used in this type of profile. The other inks in the K3 set are set to a LIMIT of 1 so that some ink goes through the nozzle but not enough to impact the overall density range of the digital negative.

The output of the Carbon 100 profile, before linearizing, is straight line. The profile may be linearized with a curve in the K, as in CURVE_K =, or the profile can be linearized with the LINEARIZE command, using either a spectrophotometer or densitometer, as in the attached profile. In fact, one method can be used over the other to allow for a general profile and specific ones for variations on the process.

The density range of the profile can be adjusted for process requirements by increasing or decreasing the ink LIMIT of the PK, Y and LK by an equal percentage. Increasing the ink LIMIT results in a higher density range, decreasing it in a lower density range.

In my own personal work I use both the Carbon 100 profile and and a multi-gray partionned system. Both have advantages and disadvantages, most of which are too complicated to discuss here. But both give really outstanding results, and are easy to adjust. And both profiles can be easily adjustment for both density range and linearity with basic QTR tools.

Sandy

The output of the Carbon 100 profile, before linearizing, is straight line. The profile may be linearized with a curve in the K, as in CURVE_K =, or the profile can be linearized with the LINEARIZE command, using either a spectrophotometer or densitometer, as in the attached profile. In fact, one method can be used over the other to allow for a general profile and specific ones for variations on the process.

Unless you have a densitometer or a spectrophotometer you should just delete the LINEARIZE command for your tests, and the linearize with the CURVE_K= line, which would in the Carbon 100 profile have the same function as GRAY_CURVE= in partionned profiles like those in the guides of Ron Reeder and Clay Harman.

I am somewhat surprised that your profile gave such a high density range that all of the steps up to 50% are pure white. But this could be explained by Cyan being a high UV blocker in your set-up.

Sandy

Hi Babak,

The high UV blocking of the cyan ink could be due to the BLB tubes. It could also be due to the negative substrate you are using. I would suggest that you test to make sure you know the cause before more testing.

Assuming the high UV blocking in your workflow is due to the BLB tubes, and is consistent, I would propose the following profile for a single value gray system where all values follow the K. The Ink Level of the PK, C, Y and LK are set to more or less give equal UV blocking at any point on the x-y coordinate, based on the palladium print from the ink separation negative you linked to.

To test, you would install this profile and print a 21 step wedge negative, then make a print with your standard exposure time, as determined with PDN. You would see one of three conditions.

1. The print is perfect, with paper white at Step 0%, and maximum density at 100%, and clear discrimination at every step from 0% to 100%. If this is the case, you proceed to the linearization stage

2. The print is too high in contrast, with many steps at paper white. If this is the case, you would need to decrease the Ink Level limit of the PK, C, Y and LK by the same percentage, and test again. This could be 5%, 10% or 20%, the only way to know is to test.

3. The print is too low in contrast, with no paper white. If this is the case you would need to increase the Ink Level limit of the PK, C, Y and LK by the same percentage.

In any event, before you can linearize the profile (map the input/output values) you will need to adjust the ink limit level to produce a print with paper white at Step 0%, and maximum density at Step 100%.

You could also use the Carbon 100 profile, and just set the Cyan limit to 1, and do the three steps above to determine ink level limits.

Hope this information is useful. If not, you may want to look in the main QTR folder and read some of the docs on how to use QTR. Unfortunately virtually none of this is directed toward the creation of digital negatives.

Sandy


#PRINTER=Quad4880
GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=100
LIMIT_K=15
LIMIT_C=20
LIMIT_M=1
LIMIT_Y=25
LIMIT_LC=1
LIMIT_LM=1
LIMIT_LK=35
LIMIT_LLK=1

GRAY_HIGHLIGHT=1
GRAY_SHADOW=1
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

Baback,

I placed the Palladium-100 text profile in the Files>Doc>QTR Profiles for Digital Negatives folder, along with a .quad view of the profile after it was installed. In the .quad view you can see how each of the four inks is linear from 0% to 100%, but with a different slope for each, which reflects the difference in Ink Level assigned.

I actually printed the profile with a 21 step wedge on Pictorico with my Epson 4880, and the log density range was 2.32 when measured with a UV transmission densitometer. I don't know what your density range requirements are for the pt/pd process you are using, but you can easily increase or decrease the contrast by changing the Ink Level up or down at an equal percentage of the four blocking inks in the profile.

At the same time I scanned the digital negative of the step wedge and also placed it in the same folder so you can see what the range of tones looks like when the DR is 2.32.

Sandy

Hi Babak,

I'm not Richard, but the densities entered should be those of the print, not of the negative. The goal here is to make a curve and/or linearization of the negative for your printing process, not to make a negative that is linear itself. 

It is also very odd that your negative densities would be not continuously increasing anywhere, so you have either a measurement error or a data entry error. In either case you should fix it manually. If print densities are not continuously increasing, it's a good idea to adjust them so that they are, otherwise your calculated Gray Curve will be wrong. 

Your negative Dmax is very low for Pt/Pd. I think this is due to the very low limit you have set for K. 

I would be happy to share with you my base curve for Pt/Pd (actually straight Pd) negs on a 3880 but didn't want to interfere with Sandy's and Richard's suggestions since it might add to the confusion. 

Cheers,
Keith

Keith Schreiber
jkschreiber.com

> On May 21, 2017, at 9:26 AM, fardy10@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> Hi Richard
> 
> I am not sure if you are still following this thread, but having followed Sandy's instructions I am now at the linearization stage and thought of your software. 
> From what I understand in the  spread sheet for the negative density, in the column marked green I should enter the densities?? I presume these are the densities of the step wedge on the transparency (transmission densities), and not the densimetry of the printed stepwedge?
> 
> 
> I did this and got
> 
> 
> 0.0100
> 0.1400
> 0.0900
> 0.1200
> 0.1600
> 0.2000
> 0.2300
> 0.2700
> 0.3200
> 0.3600
> 0.4000
> 0.4300
> 0.4200
> 0.4800
> 0.5200
> 0.5500
> 0.5900
> 0.6200
> 0.6600
> 0.7000
> 0.7300
> 
> My d max appears to be very low and I am not sure what to do about that. 
> Is this the right path?
> THe other issue is having followed sandys text file, there is no grey_curve, but a CURVE_K="0;0 100;100" line. is this where the output should go? I am sorry if these are very basic questions with regards to this software.
> 
> 
> Babak
> 
>

#Sandy First trial on normal mixture

PRINTER=Quad3880

GRAPH_CURVE=YES
N_OF_INKS=8
DEFAULT_INK_LIMIT=100
LIMIT_K=14.2
LIMIT_C=19
LIMIT_M=1
LIMIT_Y=23.75
LIMIT_LC=1
LIMIT_LM=1
LIMIT_LK=33.25
LIMIT_LLK=1

GRAY_HIGHLIGHT=1
GRAY_SHADOW=1
GRAY_GAMMA=1

CURVE_K="0;0 5;12.1273377355677 10;17.9420599219183 15;22.5975357063362 20;26.1788328148605 25;28.6197308614445 30;31.491219038554 35;34.9230636834463 40;38.1144574918807 45;41.355552057678 50;44.6767104870419 55;48.5972591869956 60;52.4602889487758 65;56.2104965891297 70;59.8668141688948 75;63.8748837892236 80;69.1166215626693 85;73.9407497465317 90;79.2202447316488 95;86.094885007615 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

Next I printed the negative and printed it, with a stoufller next to it. In the photo it is a bit dark, but in reality I can see the exposure time is spot on as I can see it is only the first step which is pure black.

http://i1337.photobucket.com/albums/o680/babaky/Platinum/sandy8withoutwell2_zps6v9trqkk.jpg

My main point is that I think this is a flawed approach. I know Sandy teaches it because it is easy for new people to use because there isn't a need to find the ink limits and partitioning points, but Using Curve_K as the only means of controlling the ink density removes several options for getting closer to a working profile.

I use the single gray value system for teaching purposes at workshops because, 1) it is very simple to explain, 2) students immediately understand how it works, and 3) it works as well, or better, with the Epson K3 inks than any two or three gray value partionned system I have ever worked with. By better I mean, 1) a very small correction curve is necessary to linearize, and 2) tones are as smooth, or smoother, with minimal grainy look. It is also very "robust" in that blockage of a few nozzles of the printer has almost no impact on overall density range or banding since at all points on the X-Y coordinate the density is formed by the same three or four UV blocking inks.

The process is very simple. One merely sets the ink levels for the three or four UV blocking inks in the ink set to establish necessary DMAX transmission for the exposure scale of your process. Then your print a step wedge print, read the input/output values, and place those in the K curve. Please have a look at the Carbon-238 quad views (with curve and not curve) that I placed in the Files section in the folder on QTR profiles for alternative printing, and note especially the very gentle correction curve that is required. You can also linearize with the LINEARIZE command, and/or the K Curve.

While other QTR tools, such as gray gama, gray highlight and gray shadow corrections can not be used with this type of single gray value system, they are essentially never needed since the original file is so close to being perfectly linear in terms of UV blocking density to begin with. And when the ink level of the three or four blocking inks is changed by an equal percentage, the actual UV blocking density will decrease or increase by the same amount at any point on the X-Y axis.

Sandy