Linearize with flatbed scanner?


#1

I can’t justify spending several hundred dollars on a spectrophotometer to linearize my prints because I only use one type of paper and just print occasionally for personal use - is there a way to use a good quality fladbed scanner to read the LAB values?


#2

Yes! On page 114 of our Piezography Deluxe manual, we provide information for measuring with a flatbed scanner under “H: Alternative Calibration Workflows”

Happy printing~ Dana


#3

Thanks, Dana - I didn’t read that far in the manual because I wasn’t making digital negatives. I followed the instructions on printing a 21-step target but when I load the 21-step Excel file and change the values to those I measured in PS, the CGATS file is for 129 steps, not 21. What should I do now? Another thing - when I measure the LAB values of the printed 21-step image, I get the “L” value, but the “a” and “b” values are all zeros.


#4

Take a look at the 21 step tool itself. You will see instructions in there.

best,
Walker


#5

Thanks Walker, but I’ve never used Excel before so I feel a bit “sluggish” - I copied the data in the CGATS into a new spreadsheet (whew!) and saved it as a tab-delimited txt file, and I’m supposed to put it in the same location as my “quad” file, but I don’t know where that is. In QuadTone RIP I blended the cool, neutral, and warm thingies to make the original print, but I don’t know how to “save” that as a quad nor where to put it.


#6

Copy and paste a curve to your desktop. Save the corrected data to the Desktop. Select both at once and drag over the QTR-Linearize-Quad droplet.

With pro you need to individually linearize the cool, neutral, and warm curves to calibrate your system.

I think you need to read the manual that is at >Piezography>Documentation. This will explain a lot of things.

Best,
Walker


#7

OK, I will definitely go back and re-read the manual, but could you clarify one more point - when you wrote:

With pro you need to individually linearize the cool, neutral, and warm curves to calibrate your system.

...does that mean that I make three separate prints of the 21-step target, with one using 100% cool, one using 100% neutral, and one using 100% warm tones?

 


#8

Yes. Three different prints: 100% cool, 100% warm, and 100% neutral.

best,
Walker


#9

Thanks Walker, will do.


#10

OK, bear with me now… I’m actually making progress. I made three prints of the 21-step target (using 100% cool, 100% neutral, and 100% warm), scanned them, then tweaked the 21_Step_Scanner_Tool for each one, and ended up with a tab-delimited txt file for each one, which sits on my Desktop. Next you wrote:

Copy and paste a curve to your desktop. Save the corrected data to the Desktop. Select both at once and drag over the QTR-Linearize-Quad droplet.

I assume that at this point I have "saved the corrected data to the Desktop", but I don't know what curve you are referring to that I should also save on the Desktop. I want to use certain percentages of the cool, neutral, and warm stock curves for my printing - do I somehow make a "curve" out of that and place it on the Desktop too?

#11

As both he manual as well as the ReadMe PDFs and installation txt at the download page say, your curves live in >Piezography>Curves>(your printer/ink combo)>

best,
Walker


#12

I copied the three linearized txt files to my Desktop, and also copied the cool, warm, and neutral curves that I use to the Desktop. Then I selected to cool txt and the cool quad files and dropped them on what I hoped was the “QTR-Linearize-Quad droplet” (QTR-Linearize-Quad.exe in the QuadTone RIP/Eye One folder) but I got the message “The Lab values are not in order. Cannot be linearized.” Where did I go astray?


#13

please zip and upload all of them here so I can take a look.

 

best,

Walker


#14

Here they are.

jversyp.zip (10.4 KB)


#15

Please also zip the 21 step tool in it’s current state and upload that too. (or just upload a few of the original measurement files).

 

Thanks,

W


#16

Here’s the 21-step tool.

21.zip (50.6 KB)


#17

I guess you didn’t understand what I was looking for. I need to see the numbers that you typed into the green rows not just the same tool that I have

It’s ok, if you haven’t saved the tool . . . you probably either typed the wrong numbers into the green rows or typed in some other cells.

Try doing over. If you type the numbers in only the green cells it shouldn’t give you any errors.

Copy and past the corrected “CGATS” data from the excel into a text editor, not into another spreadsheet. If you have to copy and past into a spreadsheet remember to “paste special, values only”

 

best,

Walker


#18

My inexperience with Excel got the best of me and it copied more data than was necessary. I re-measured and put the CGATS info into a text editor and zipped all of my files.

jversyp-1.zip (14.2 KB)


#19

Ok. I took at a look.

Almost there.

You want to copy A1 through D137 of the CGATS sheet when you create the txt file that you use to drag and drop over the QTR-Linearize-Quad.

The instructions say “copy and paste the sheet … and save as tab delimited” which works as well. It does not say to only copy the numbers though. That won’t work.

I suggest copying A1 through D137 and pasting this into a new txt file. Save this as “corrected.txt” to a new folder on the desktop and then drag the .quad you want to linearize into that folder as well and then select both and drag these over the QTR-Linearize-Quad droplet. This will create the new -lin.quad file which you can put back in your curves folder. After adding the new curve(s) click your install command again to update the curve list in your driver.

-Walker


#20

I followed your instructions and the cool quad and the neutral quad came out fine, but I can’t get the warm files to turn into a -lin.quad file - can you look at the two files I zipped and see if you can tell me what’s wrong?

 

Thanks!

Jim

warm.zip (3.25 KB)