In the “Create Curves” tab of Idealink, there is a check box bottom right, to “turn on” Gray Balance. According to the manual, this is essential for any devices, inkjets or presses. Aside of this check box is a button for “Gray Options”, when clicked gives you 2 choices for Paper White-either white of the current paper, or Custom White-a0_b-2(GRACoL specs). I have been using the white of the paper, not he GRACoL spec. Underneath these choices is another box for “Smoothed Gray Balance” and another box for "Reduce Gray balance when cyan>50%. I change the 50% value to affect gray balance up 75% and leave “Smoothed Gray Balance” unchecked. I was wondering what settings other users use when you create curves for a offset press.
While I can’t speak to other users settings, I can take this opportunity to explain these last two fields you mentioned: “Smoothed Gray Balance,” and “Reduce Gray balance when Cyan > [ 50 ]%”
With Smoothed Gray Balance checked, Curve uses fewer points along the scale from 0 to 100 to get information on producing the curves. This results in a smoother curve, changes are not so dramatic. This is recommended for an offset press. When smoothing is unchecked, the curves will be more complex. (The manual has more information on this.) And this is more suitable for printers with more stable and repeatable gray balance like inkjets.
“Reducing Gray balance”:
This was a control that was added after the 1.0 version was made, and this feature is not documented in the manual, so I’ll try to explain it a bit here. You’re not going to want your curves to try to restrict your 100% CMY to a perfect gray balance. To do that would severely restrict some colors in the rest of the spectrum. Therefore, when the curves are made they will necessarily taper off the gray correction as they get darker. By default, Curve does this in a smooth way, starting at 50% to feather the corrections so that the curve to CMY at zero is not too abrupt. The control was added so that you could add more gray correction to shadows, although this might result in a faster, more abrupt transition to black.
So your setting of 75% is probably okay if you are looking for more true gray in the shadows, and are willing to sacrifice a more sudden transition to black.
There’s been a bit of a change in the recommendation of the smoothed gray balance option since the release of Idealink Curve v1.0. It had been on by default and recommended for offset presses. With v1.1, it is off by default, and is now only recommended if the device has unstable or non-repeatable gray balance (I’m inferring this recommendation based on proposed amendments for G7 in 2008), which doesn’t always describe an offset press. An alternative to using smoothed gray balance would be to measure and average many sheets from the pressrun.
Although this option reduces the number points used to adjust gray balance, it may or may not result in “smoother” actual gray balance
My experience with smoothed gray balance with offset presses has not been positive overall, often actually introducing an imbalance in one area based on the wholistic correction curve it generated. So I would recommend that it not be used unless you only have a sparse sampling of the pressrun that exhibits unstable balance, and cannot average more sheets. In short, don’t assume that an imbalance on press equates instability and automatically click the smoothed gray option.