CHROMiX

TVI adjustment to match presses

I’m trying to match an uncoated conventional press up with an uncoated UV press. I don’t think the normal gray balance curve will work because it won’t compensate for the differences in gain. I tried to follow the procedure outlined in Appendix F to get custom TVI curves for the UV press which I would then load in to calibrate the conventional press, but the number in the CGATS file are the gray balance correction, not the actual TVI from the press. Any idea what I am doing wrong ?

Appendix F should get you where you need to be.
Here are the steps to follow:

  1. With ANY P2P loaded in Curve (it doesnt have to be from the same device), go to the Create Curves window and select the desired number of Control Points.
  2. Click the Export button and save a CGATS file.
  3. In Excel, replace the output percentages for each color with the WANTED percentages, where WANTED % = TVI plus Index %, and Index % = the control point percentage (left column).
  4. Save as a Text file.
  5. Load the text file with the “load custom” button found in Curve in the Setup area for TVI.

So I would need to measure the TVI values with a densitometer ?

I thought the software would calculate the TVI from the P2P target.

I’m not sure your plan here is the best way to get what you’re looking for.

First, Curve (and G7) should do a good job of “matching TVI” between presses if the first press, the “uncoated conventional press” is calibrated to G7 in the first place. It does compensate for the differences in gain that you are referring to.

Curve calculates correction curves to get a press printing using the G7 tone curve shape. It also (optionally) gray balances those curves. So if both presses use G7, their tone curves (gain taken into consideration) should be very similar.

The difference between them may be when one press prints to a higher density than the other. G7 scales to the density of the press it’s calibrating and keeps the highlights very similar so they keep a similar appearance.

Curve3 also offers TVI calibration if you want to do without G7, but I recommend you use G7 on both presses to get the closest visual match, both in tone curves (gain) and gray balance.