Where does ink optimization software fit in G7 process?

[roger]

When we apply ink-optimizing (high GCR) profiles to our printing, we've widened the tolerances for where CMY can print. Yes, black is now Key but what happens to the whole idea of G7 calibration and the importance of gray balance if we're no longer printing our grays with YMC?

and secondly, if high-GCR separations are all so great on press (save ink, improved stability and runnability on press, ect) why aren't the standard profiles (those bundled with Photoshop and others available for download) built with more GCR?

thanks in advance for your thoughts,

Roger Schutte
J.S.McCarthy Printers

 

[meddington]

...what happens to the whole idea of G7 calibration and the importance of gray balance if we're no longer printing our grays with YMC?

Great question, and one sure to raise a point or two regarding the disconnect between the live image area and control elements on a press sheet. The importance of calibration is still there whether utilizing one dimensional curves, near-neutral calibration or device-link/ink optimization. It all comes back to the three "C"s of colorrmanagement...calibration, characterization, & conversion. The calibration step allows fine tuning of a device to a desired result, as well as a basis for readjustment if/when the device drifts from said basis. Regarding the increased "tolerances" for CMY with ink optimization, I'll agree with you. Using ink optimization in our plant, our make readies have in some cases become formalities as the proof and press sheet tend to visually match before the press operator has finished tuning ink keys. However, not all imagery is as static as others, and having colorbars that are free from ink optimization adjustments help give early indication of printing issues, in some cases before they become visual issues on the printed sheet.

Just curious, are you optimizing your colorbars/control elements as well?

... why aren't the standard profiles (those bundled with Photoshop and others available for download) built with more GCR?

Not all printers are comfortable printing with heavy GCR, nor are all substrates possibly optimal for the amount of black ink introduced by heavy GCR. Plus, the SWOP profiles are used quite extensively, often for other print processes where they might not be appropriate...I would not want to supply a flexo printer with a heavy black channel for instance. We supply far more files than we print, and some third party printers are very reluctant of heavy amounts of GCR. I worked with a printer recently who was adamant that we not supply with a full black channel as they were confident in there ability to match a Gracol proof with standard separations, and were leery of fleshtones, etc, filling in on press. After the initial printing of the catalog, which I would not classify as a consistent pressrun, they then decided to try heavier GCR separation and were quite pleased with the results.

 

[gordo]

Great question, and one sure to raise a point or two regarding the disconnect between the live image area and control elements on a press sheet.

Was that my phone ringing?

Gray balance (what the G7 method is for) is still needed in the initial setup of the press condition. However gray balance is pretty much a myth as far as a press control metric.

More detail on why the sacred cow of gray balance should be made into burgers is available here:
Quality In Print: Grey Balance Unbalanced – An inconvenient truth, part 1 of 2
and here:
Quality In Print: Grey Balance Unbalanced – An inconvenient truth, part 2 of 2

Not all printers are comfortable printing with heavy GCR, nor are all substrates possibly optimal for the amount of black ink introduced by heavy GCR.

Note that pretty much all color separations are done using GCR since the default separation profile in PShop uses GCR. So, ink optimization software basically increases the level of applied GCR rather than change the separation from UCR to GCR.

GCR separations rely heavily on the ink lay down quality of the black printer. Unfortunately, in some applications like newspaper printing, the ink used and its transfer condition is not always the best. This is also why GCR failed when it was initially introduced in the 1970s. Conditions are different now though. As meddington notes, the whole process needs to be considered.

best, gordon p

 

[rich apollo]

When we apply ink-optimizing (high GCR) profiles to our printing, we've widened the tolerances for where CMY can print. Yes, black is now Key but what happens to the whole idea of G7 calibration and the importance of gray balance if we're no longer printing our grays with YMC?

Doesn't change a thing. You've just given yourself more control over those grays. Printing a neutral 3-color gray is kinda' like riding a wheelie: it's exhibits a great amount of balance and control, but on the whole is a pretty impractical way to travel.

and secondly, if high-GCR separations are all so great on press (save ink, improved stability and runnability on press, ect) why aren't the standard profiles (those bundled with Photoshop and others available for download) built with more GCR?

A lot will depend on the final production process. We've found that paper and screening greatly impact how we reseparate.

 

[meddington]

. Printing a neutral 3-color gray is kinda' like riding a wheelie: it's exhibits a great amount of balance and control, but on the whole is a pretty impractical way to travel.

Quote of the week

 

[Lukas Engqvist]

I did write an answer wich got lost in an interuption, but I do want to say that there is a value in printing consistently even in the 3 colour grey. Why beacuse it gives us an indicator of the tertiary colours.

I do see Gordo's point, and we do not use the greybalance built into our system because it is based on way too few variables. but I do have a split patch of grey balance and k only as a built in thermometer.
I use the analogy of a thermometer, because just as after a long work out i would consider it natural to have sweaty forehead, but not for beads of sweat to be forming under every hour of the day.

So it is not just a trick to show of, but a signal…*like when a farmer would look at the sky and know how to plan his day, a grey balance that is off doesn't need an over reaction, but gives a heads up…*if there is an explanation, as extreme colour then fine, but if not we can begin to look at what might be causing the change.

I also want to mention there are some spacial cases when a CMY is prefered over a heavy GCR. On our presses a 2-20% K only can become grungy if printing second side, this normaly when in combination with heavy images that require a large amount of spray. In those cases CMY will give a smoother print. Also greyscale images with a 10-20% CMY fill in will give much richer detail, but this requires CMY balance to be reasonable. One more instance is delicate skin tones or light coloured woods and watercolour paintings where black raster would become unbecoming in the light tints.

To let the grey drift because the images are more tolerant is a slippery road to go down.
In short I agree with what is said, but just want to be sure we are not getting too slack

 

[meddington]

One more instance is delicate skin tones or light coloured woods and watercolour paintings where black raster would become unbecoming in the light

The process at hand, the quality of the consumables, and the competency of the press crew will be a large determining factor in the success of GCR/ink optimization. We've applied it across the board on light ivories and pastels as well as fleshtones with great results. We even use it for separation for food packaging (offset) and to underwear Catalogs.

Then again, I recently came across a cereal box with an image of a mother and son on the front panel who looked like they had rolled around in the dirt before the photoshoot. Heavy GCR in the wrong hands can look real bad.

Neat trick to try on a press run using heavy GCR is to rub the wet ink on the press sheet (before coating is applied) and watch tones that seemingly have little or no black in the separations smear gray. Evidence that any amount of slur on the black printer can ruin your day.