Improving on linearization


#1

I just finished my first linearization for palladium and while everything went very smoothly, the print of the 21-step shows it could be more linear. I was hoping someone on the forum could help me figure out where I might have gone wrong, or if there is anything I can do to improve on it. I’ve gone through the whole process twice but with roughly the same results.

Here is the 21 step tablet I printed (iPhone pic), along side with bull’s eye for smoothness, which is what I do with every linearization:
Here is the 21-step checker data provided by Piezo DN:
Here is my 21-step checker, which i use with optical density. I might be old school, but optical density makes a lot more sense to me!
Here are the steps I took:
Medium: Palladium + FeO / no Na2
Paper: Hahnemuhle Platinum Rag
Hardware:
Mac OS X El Capitan
QTR Print tool
Colormunki / Color Checker spot mode
Steps:
1. I printed the LIMITER at my standard printing time. 255 was pure white; 254 had visible tone, which my optical densitometer could not pick up. The manual says that if only 255 and 254, you do not need to limit. So I did not.
2. I printed a COLORMUNKI 129-step target using a renamed copy of the master negative curve. I got a very nice range of grays (see below). Took a reading with the colormunki in color checker, using spot mode. I had to redo it, making sure I was centered each time with the target. Exported the data and pasted in them in the 129STEP_PIEZODN_CGATS_SMOOTHER.xlsb spreadsheet.
There were a number of L* false, especially in the 38 to 40 range so i corrected them all. Separation at top and bottom was adequate so didn’t need adjustment as per instruction.
Here is an iPhone scan of the target, the colormunki patches and screen grab of SMOOTHER excel sheet:
Copied the data in a spreadsheet, etc… and used the linearize-quad applet. A new curve was created with the extension -lin, which I used for printing the above 21-step.
Any help would be greatly appreciated! I really like the whole process, I am finding it very straight forward. But i would love to aim to a more linear output.
I am attaching the colormunki data, along with the -out.txt generated when installing the curve.
Many thanks and best wishes,
Gilles

ColorMunki.csv (46.4 KB)

Workbook3-out.txt (11.5 KB)


#2

It looks like you are using an exposure unit that significantly increases the narrow 360nm UV bandwidth thus creating this very dark first exposure compared to what the master and original PD curve was calibrated for.

I suggest you re-coat and then iteratively linearize this second (semi-calibrated) curve using the same workflow.

Control for humidity, etc.

Lastly, make sure you have taken the holder sleeve off of your Munki or it will be reading the patches too far off the paper.

best,

Walker

 


#3

Thank you for the prompt reply Walker! So I can repeat the 129-step procedure more than once and create a -lin-lin quad? I thought you could only do it once… Indeed i’m using a 1500W bulb with a peak around 390 to 430nm. What type of lighting was the Master calibrated for?

As much as possible is under control in my darkroom, RH%, time, temperature, chemistry, etc… The munki is out of sleeve and i take the time to make the readings to avoid any false reading.

Thanks again, Gilles


#4

Can you tell us how you determined you Standard Printing Time? Regardless of the wavelength of the UV lightsource, it looks like you are over exposing?

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#5

Can you tell us how you determined you Standard Printing Time? Regardless of the wavelength of the UV lightsource, it looks like you are over exposing?

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#6

Thank you for your comment J. Scott King; can you explain what makes you say i’m over exposing? I am getting separation right from the darkest patches on the 129-step and a little too much on the linearized version. If I was over exposing, my shadows would be blocked.

I’ve been using this standard printing time for a while now and made an excellent linearization from it for this process and paper. But I did double-check it when starting with Piezo DN and used the method recommended by Walker, by exposing a blank sheet of film and running steps in 1/3 stops increments. I ran the test twice and I could actually increase the exposure a little to achieve a little more black, but i decided not to push it. My dmax would drop if I would expose any less. I’m not used to working with Lab, so perhaps you are seeing something I don’t.

Thanks again, Gilles


#7

[quote quote=25719]Thank you for your comment J. Scott King; can you explain what makes you say i’m over exposing? I am getting separation right from the darkest patches on the 129-step and a little too much on the linearized version. If I was over exposing, my shadows would be blocked.

I’ve been using this standard printing time for a while now and made an excellent linearization from it for this process and paper. But I did double-check it when starting with Piezo DN and used the method recommended by Walker, by exposing a blank sheet of film and running steps in 1/3 stops increments. I ran the test twice and I could actually increase the exposure a little to achieve a little more black, but i decided not to push it. My dmax would drop if I would expose any less. I’m not used to working with Lab, so perhaps you are seeing something I don’t.

Thanks again, Gilles

[/quote]

Gilles, it sounds like you followed solid procedure to establish Standard Printing Time. In the attachments, I thought I was seeing blocking in the shadows of the Colormunki patches and the data of the CGATS smoother tool. Also, I’m surprised these monochromatic inks would be so sensitive to UV wavelength; I have experienced that with PDN, but thought with the densities we achieving with PiezoDN that would not be the case.

Maybe you will need to modify the master curve. That’s beyond my current experience and will wait for Walker or Keith to comment.

-Scott


#8

I have seen this curve (dark exposure) happen on some people’s bulbs and not on others. We saw it when transitioning between our old 16x20 table-top exposing unit (with a bulb that is more spread-out with its spectrum, and which is what we built the masters for) and our newer platemaker with the doped metal halide bulb. (The masters are built to work with LED and Tube UVs, etc. The most common UVs.)

When linearizing from such a dark point, one must do at least two iterative lins as the first one will not be perfect due to the amount of distance the adjustment must travel.

No need for a different master. The curves we were using at that last PiezoDN class (that you were in Scott) were double iterated from the original much thinner master as well and went perfectly linear eventually. They only have to be tweaked every few months at this point as small environmental changes naturally occurs within the chain of printing.

 

best,

Walker


#9

Thank you Walker, it is good to know you can repeat the procedure and build up the linearization. I especially like the fact you can fine tune the linearization down the road, without having to start from the beginning. Indeed there are so many factors involved, things always change with time… I shrug every time I have to start a new batch of paper, a new roll of picto, make a new batch of ferric…! This will simplify things in the long run.


#10

[quote quote=25720]

Thank you for your comment J. Scott King; can you explain what makes you say i’m over exposing? I am getting separation right from the darkest patches on the 129-step and a little too much on the linearized version. If I was over exposing, my shadows would be blocked. I’ve been using this standard printing time for a while now and made an excellent linearization from it for this process and paper. But I did double-check it when starting with Piezo DN and used the method recommended by Walker, by exposing a blank sheet of film and running steps in 1/3 stops increments. I ran the test twice and I could actually increase the exposure a little to achieve a little more black, but i decided not to push it. My dmax would drop if I would expose any less. I’m not used to working with Lab, so perhaps you are seeing something I don’t. Thanks again, Gilles
Gilles, it sounds like you followed solid procedure to establish Standard Printing Time. In the attachments, I thought I was seeing blocking in the shadows of the Colormunki patches and the data of the CGATS smoother tool. Also, I’m surprised these monochromatic inks would be so sensitive to UV wavelength; I have experienced that with PDN, but thought with the densities we achieving with PiezoDN that would not be the case. Maybe you will need to modify the master curve. That’s beyond my current experience and will wait for Walker or Keith to comment. -Scott [/quote] I try Scott, but when I'm the forest you don't always see all the trees; so I always welcome feedback!