G7 ?

[Green Printer]

If your inks have much less dot gain and trap better than the G7 specs what do you change to get to G7 specs?

 

[meddington]

If your inks have much less dot gain and trap better than the G7 specs what do you change to get to G7 specs?

Dot gain can be "controlled" via CTP curves. If you can't hit the overprint traps within a reasonable tolerance, you could consider color management (device link conversion).

 

[Green Printer]

When I print put a 50% dot on the plate and it prints at 55% does G7 have any rules for this?

 

[meddington]

When I print put a 50% dot on the plate and it prints at 55% does G7 have any rules for this?

Not directly. TVI (Dot gain) is used as a process control metric, but no outright dot gain targets are utilized. When looking at dot gain, you might look for "nesting" of the individual curves, meaning dot gain CMYK channel should be relatively similar. Significantly higher or lower channels could indicate a problem.

G7 defines a Neutral Print Density Curve (CMY gray balanced tonal curve) to define tonality as this is a more direct measurement than dot gain. Here's a link to learn more: IDEAlliance

 

[Green Printer]

Not directly. TVI (Dot gain) is used as a process control metric, but no outright dot gain targets are utilized. When looking at dot gain, you might look for "nesting" of the individual curves, meaning dot gain CMYK channel should be relatively similar. Significantly higher or lower channels could indicate a problem.

G7 defines a Neutral Print Density Curve (CMY gray balanced tonal curve) to define tonality as this is a more direct measurement than dot gain. Here's a link to learn more: IDEAlliance

What if you can acheive all the specs at lower densities.

Black 1.50
Cyan 1.25
Mgenta 1.30
Yellow 0.95

 

[meddington]

What if you can acheive all the specs at lower densities.

Black 1.50
Cyan 1.25
Mgenta 1.30
Yellow 0.95

Solid ink densities are not defined by G7, so if you hit all the defined targets (Solid ink Lab values, NPDC, etc) you should be in spec.

Further, the defined G7 tonality is dynamic based on achievable end density. Curve shape is relatively constant from highlight to midtone for most processes, than scaled toward the achievable end density. Individual solid ink densities are not defined, but rather the solid Lab values for the particular paper type.

 

[gordo]

What if you can acheive all the specs at lower densities.
Black 1.50
Cyan 1.25
Mgenta 1.30
Yellow 0.95

What are the specs that you say you are achieving?

thx, gordon p

 

[Lukas Engqvist]

With low densities you will get high trap values. This is one of the balances to find target densities where you get bright enough primaries and still are able to maintain the trapping targets. Look at the Lab values of primaries and secondaries to see if you have the right target. Note that if you increase your densities you will most likeley get higher dot gain.

 

[Green Printer]

What are the specs that you say you are achieving?

thx, gordon p

Gray balance, trap, etc. but not density according to various brands of densitometers.

Visually the density appears the same as calibrated color test swatches from various suppliers.

 

[gordo]

Gray balance, trap, etc. but not density according to various brands of densitometers. Visually the density appears the same as calibrated color test swatches from various suppliers.

If you want your presswork to be printshop specific, i.e. unique to you - then it does not matter what numbers you achieve - as long as you are happy with the result. However, if you are targeting an industry print specification, you cannot take parts of the specification in isolation.
For example, you can achieve grey balance with quite a variety of CMY hues - this does not mean that you can achieve the color gamut of an industry specification or "match" a proof that has been made to represent and industry specification. So, in this case, achieving grey balance would be meaningless.
A dot gain of 5% means that your tonality in press will not align with any industry specification. Compared to industry specs your presswork would look washed out - particularly at the SIDs you are running. Visually assessing solid densities is not useful since our eye/brains have very poor discrimination of saturated colors.
SIDs like yours
Black 1.50
Cyan 1.25
Magenta 1.30
Yellow 0.95
also suggest that you also are likely reducing your potential press gamut. The ink film that you are running at those densities may also put your press in an unstable condition which could result in greater color variation through the run than might otherwise happen.

best, gordon p

my print blog here: Quality In Print current topic: Revealing DSLR dust bunnies

 

[indy jones]

I am having the similar situation. I can hit the G7 lab values for the primaries and secondaries. If I am using Delta 94 on measure tool comparing it to G7 data set. If I compare it to Delta E we are off in the secondaries. Which one do I use to qualify ink?

 

[Green Printer]

If you want your presswork to be printshop specific, i.e. unique to you - then it does not matter what numbers you achieve - as long as you are happy with the result. However, if you are targeting an industry print specification, you cannot take parts of the specification in isolation.
For example, you can achieve grey balance with quite a variety of CMY hues - this does not mean that you can achieve the color gamut of an industry specification or "match" a proof that has been made to represent and industry specification. So, in this case, achieving grey balance would be meaningless.
A dot gain of 5% means that your tonality in press will not align with any industry specification. Compared to industry specs your presswork would look washed out - particularly at the SIDs you are running. Visually assessing solid densities is not useful since our eye/brains have very poor discrimination of saturated colors.
SIDs like yours
Black 1.50
Cyan 1.25
Magenta 1.30
Yellow 0.95
also suggest that you also are likely reducing your potential press gamut. The ink film that you are running at those densities may also put your press in an unstable condition which could result in greater color variation through the run than might otherwise happen.

best, gordon p

my print blog here: Quality In Print current topic: Revealing DSLR dust bunnies

If it is possible to print on a consistent basis with less dot gain and still achieve gray balance and color gamut what needs to be changed? I have had the ink altered and dot gain went up and it met G7 at densities of

BK 1.70
Cyan 1.40
Magenta 1.50
Yellow 1.00

We consumed 15% to 20% more ink to get at these figures.

Are the present standards based on 20 year old pressroom technology?

Is it time to change industry standards to be able to lower ink consumption?

 

[meddington]

Is it time to change industry standards to be able to lower ink consumption?

*cringe* Now you've went and opened it up to the GCR/Optimizers venders.

 

[Green Printer]

With a controlled pressroom all you need is the solid hue values and trap. When you have established this two parameters everthing else can be contolled by a color profile or gain curve or whatever you want to call it.

If you know a 50% dots prints at 55% but you want 65% for G7 why not adjust your plates to get to the G7 value.

Don't fool around with the ink or chemistry keep these a constant. Do all your adjusting with profiles.

 

[gordo]

Are the present standards based on 20 year old pressroom technology?
Is it time to change industry standards to be able to lower ink consumption?

I'm sure that the GCR/Optimizers vendors will graciously not post to this thread ;-)

The standards have been around much longer than 20 years, and there certainly could be an opportunity to rethink the standards with, for example, direct imaging digital presses – however I doubt that will happen.

Print standards were developed and refined over time as a response to the need to reproduce original art in as cost-efficient manner possible given the limitations of inks, substrates, plates etc. That's why in "full" color printing we only use 3 chromatic inks rather than 6 (or more). You could make the argument that by only using 4/C process you've already reduced your ink consumption by at least 40%. If you reduce your SIDs, yes, you will use less ink, however your ability to reproduce original art will be compromised. The same thing happens if you target a lower dot gain.
If you want to reduce ink consumption while maintaining your ability to meet industry standards and specifications, you can do so by the separation techniques that you use (first generation and reseparation) as well as the halftone screening method (for example 20 micron FM will reduce your ink consumption by around 15% compared to 175-200 lpi AM/XM).

It's a business, rather than technical decision.

best, gordon p

my print blog here: Quality In Print

 

[gordo]

With a controlled pressroom all you need is the solid hue values and trap. When you have established this two parameters everthing else can be contolled by a color profile or gain curve or whatever you want to call it. If you know a 50% dots prints at 55% but you want 65% for G7 why not adjust your plates to get to the G7 value. Don't fool around with the ink or chemistry keep these a constant. Do all your adjusting with profiles.

Not sure if I understand you correctly, because in fact, although some do – the vast majority of printers don't fool around with the ink or chemistry to effect dot gain. They do all their adjusting with profiles and/or with plate calibration curves.

best, gordon p

 

[Deleted member 16349]

I was just listening to the webcast at the Graphic Arts Online web site. It was about G7. Don Hutcheson gave a very good talk on his method. I have to say that when ever I have heard him discuss his system, he is very honest about what it does and what it can not do. People should actually listen to what he says and not imagine that he claims more than what he says.

Anyhow, one of the techniques struck me and I hope there are G7 experts here who can answer a question.

He had a slide that showed the idealized NPDC curve on graph paper. At one point he was discussing how to adjust the rip for gray balance by determining how far off the C, M and Y curves were and then using that to obtain data for adjusting the individual CMY curves in the rip. (I think)

My question is: Are these curves measurements of the CMY densities in the gray patches of the P2P strip?

The graph paper has the vertical axis labeled as Neutral Printed Density but in order to get separate CMY curves, I am assuming that the patches are measured with the individual CMY density channels and used to plot the CMY curves.

 

[meddington]

My question is: Are these curves measurements of the CMY densities in the gray patches of the P2P strip?

The graph paper has the vertical axis labeled as Neutral Printed Density but in order to get separate CMY curves, I am assuming that the patches are measured with the individual CMY density channels and used to plot the CMY curves.

Actually, the cmy values are derived from the cmy triplet values that yield a neutral gray. You would measure the "grayfinder" target to find the patch that is nearest the target gray lab values (optimally 50C 40MY). If patches other than 50C 40MY are closer to neutral, you could then plot the values to determine needed compensation. This is explained more thouroughly in section 8 of the G7 how to guide.

 

[Deleted member 16349]

Actually, the cmy values are derived from the cmy triplet values that yield a neutral gray. You would measure the "grayfinder" target to find the patch that is nearest the target gray lab values (optimally 50C 40MY). If patches other than 50C 40MY are closer to neutral, you could then plot the values to determine needed compensation. This is explained more thouroughly in section 8 of the G7 how to guide.

Are the cmy triplet values the three density values for cmy?

I will go to the guide to get more info but it would be nice to know that we are talking density for that plot. Just wanting clarification since I know that measuring a screen patch and getting three values of density for the CMY channels has no direct relationship with the three CMY inks.

 

[meddington]

Are the cmy triplet values the three density values for cmy?

I will go to the guide to get more info but it would be nice to know that we are talking density for that plot. Just wanting clarification since I know that measuring a screen patch and getting three values of density for the CMY channels has no direct relationship with the three CMY inks.

Hi Erik,
You are correct that CMY density has no direct relationship and would be a poor way to go for determining ideal gray. However, the "triplet" values are not density values, but patch color percentages. Think of it this way. 50C, 40MY is the optimal value to yield the neutral gray (according to G7), but if that patch doesn't actually measure neutral (in CIELab, not density) from your press/printer, perhaps a 50C, 38M, 43Y does. The GrayFinder target has patches of differing CMY percentages to help determine the optimal compensation toward gray.