Your OUT (Delta) data looks like decimal percentage values. However, if these are 8-bit values, you should round them to integers.
By the way, your case is similar to those I have encountered in cooperation with engraving companies in Europe. My company produces polymer plates for flexo printing as a supplier and most of them are in G7 calibration. However, when everything is clarified with the engraving company on the G7 topic - you will see how stable these curves are in rotogravure printing.
Original Message:
Sent: 07-26-2024 03:09 AM
From: Lee-Seul Choi
Subject: "In gravure printing, how are the curve values from 0 to 255 obtained when applying them using the HelioDisk software for the cylinder?"
Thank you for your reply.
I have modified the data according to your advice and forwarded it to the cylinder manufacturer.

The cylinder manufacturer said that the numbers were ridiculous and that they would rather correct them and send them to me, but I want to check the printed version to see how ridiculous it is, so I am currently correcting the cylinder.
I will write again once the printing is completed with the revised cylinder.
*For reference, the flexo printer is also performing G7 at the same time (the resin plate is also commissioned to a specialized manufacturer), and unlike the gravure printing, it is progressing in a positive direction without any blocking due to the resin plate curve value.
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Lee-Seul Choi
UWRAPCO
82-10-7159-6971
Original Message:
Sent: 07-24-2024 06:13 AM
From: Wojciech Bialkowski
Subject: "In gravure printing, how are the curve values from 0 to 255 obtained when applying them using the HelioDisk software for the cylinder?"
Step by step procedure.
1) Select Run 1 - Calibration in the Runs window
2) Select Based On: Linear (none)

3) Make a measurement, preferably several, e.g. P2P51characteristics, or load the measurements.
4) Set the G7 calibration parameters - Printing Aims, White/Black Gray Balance.
then:

5) Select 8bit_Decimal_List (attached to the post).
6) Select Delta
7) Export as CGATS

8) In Excel, convert Decimal to 8bit with rounding to intiger.
Formula for column IN 'Sample_Name': (100 - decimalIN) x 2.55
Formula for Delta Value: decimalDelta / (100/255)
Delta data has positive and negative values, therefore a different formula keeping positive or negative values.

You can hide the % columns and specify only 8 bit for the convenience of engraving shop operators. Of course, send him the Excel file and then he can enter "his secret OUT" data into the table and immediately calculate the new value.

9) Send the data to the engraving shop. Since we do not know which bits are used as IN in HelioDisk, they must read the correction value for a specific IN bit from the sent table.
Important! In this case of an unknown curve, always follow the procedure given above, even if it is the next iteration.
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Wojciech Bialkowski G7 Expert
Studio Omega
Bydgoszcz
Poland
Original Message:
Sent: 07-24-2024 04:03 AM
From: Lee-Seul Choi
Subject: "In gravure printing, how are the curve values from 0 to 255 obtained when applying them using the HelioDisk software for the cylinder?"
Thank you for your response.
- I don't know the HelioDisk curve values that were applied to the Initial cylinder. The gravure cylinder manufacturer said that it could not provide the applied curve value, and the photo below will be provided simply as a reference for the HeliDisk curve value format.

- So, after scanning the printed material, I have to estimate the previously applied HelioDisk curve value with the tone value from 1 to 100 (curve value + delta value) obtained from curve4.



- The gravure cylinder manufacturer said that they would modify the cylinder themselves using the tone values from 1 to 100 obtained from curve4 and send it to them. But I want to go as far as trying it myself.
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Lee-Seul Choi
UWRAPCO
82-10-7159-6971
Original Message:
Sent: 07-23-2024 02:45 PM
From: Wojciech Bialkowski
Subject: "In gravure printing, how are the curve values from 0 to 255 obtained when applying them using the HelioDisk software for the cylinder?"
As for companies that engrave cylinders, they are very conservative. Because their tools are from a "previous era".
I suggest you do not make any changes to the curve in HelioDisk and add an intermediate stage.
Take the finished Repro PDF file and perform the separation using the DEVICE LINK profile generated in Curve4 with Linear selected as the base curve.
Similarly, you can also add curves to a ready-made 8 bit TIFF file, e.g. in Photoshop, using correction layers with the curve from the .acv file generated in Curve4.
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Wojciech Bialkowski G7 Expert
Studio Omega
Bydgoszcz
Poland
Original Message:
Sent: 07-20-2024 11:50 PM
From: Lee-Seul Choi
Subject: "In gravure printing, how are the curve values from 0 to 255 obtained when applying them using the HelioDisk software for the cylinder?"
1.I scanned the gravure print and used the Curve4 software to obtain tone curve adjustment values ranging from 0 to 100.
2.However, the cylinder plating company uses curve values ranging from 0 to 255. Therefore, to adjust the cylinder curves, they require curve values that can be applied in the HelioDisk software.
3.I tried simply converting the values from 0–100 to 0–255, but the results were incorrect.
4.Can I determine the curve values suitable for HelioDisk using the print materials I have, along with i1Pro and Curve4 software?
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Lee-Seul Choi
UWRAPCO
82-10-7159-6971
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