4 Color Process Color Bar examples

[z284pwr]

Looking to see what different print shops are using as far as 4 color process color bar information to help with color matching/densities.

I'm working in a Forms Printing Plant which is mostly 2-3 Spot color bank form and check printing so we don't come across many 4-color jobs. However we are starting to branch out into 4-color process Personal Checks. We are printing on a Rotatek RK-250 Plus with computer controlled registration but with the press setup for forms printing we don't have anything on the press for color matching/density control just densitometers to read from.

Currently we are just doing color bars consisting of a 25/50/75/100% screen value for the CMYK values.

 

[gordo]

Looking to see what different print shops are using as far as 4 color process color bar information to help with color matching/densities.

I'm working in a Forms Printing Plant which is mostly 2-3 Spot color bank form and check printing so we don't come across many 4-color jobs. However we are starting to branch out into 4-color process Personal Checks. We are printing on a Rotatek RK-250 Plus with computer controlled registration but with the press setup for forms printing we don't have anything on the press for color matching/density control just densitometers to read from.

Currently we are just doing color bars consisting of a 25/50/75/100% screen value for the CMYK values.

You can read a4 part explanation of color bars by following these links:

Quality In Print: The Color Bar - Part 1 of 4 - Background
Quality In Print: The Color Bar - Part 2 of 4 - Color Bar Elements: Solid Ink Targets
Quality In Print: The Color Bar - Part 3 of 4 - Color Bar Elements: Forensic Targets
Quality In Print: The Color Bar - Part 4 of 4 - Color Bar Application

Basically, solid ink density patches are what the press operator uses in day to day production. The other possible patches (and there are many options) are typically used forensically - i.e. to figure out what went wrong if the presswork does not meet expectations.

best, gordo

 

[z284pwr]

You can read a4 part explanation of color bars by following these links:

Quality In Print: The Color Bar - Part 1 of 4 - Background
Quality In Print: The Color Bar - Part 2 of 4 - Color Bar Elements: Solid Ink Targets
Quality In Print: The Color Bar - Part 3 of 4 - Color Bar Elements: Forensic Targets
Quality In Print: The Color Bar - Part 4 of 4 - Color Bar Application

Basically, solid ink density patches are what the press operator uses in day to day production. The other possible patches (and there are many options) are typically used forensically - i.e. to figure out what went wrong if the presswork does not meet expectations.

best, gordo

Thanks for those links, definitely points me in the right direction. Under part 2 in the comment section there was a comment about this:

For presswork in North America - the target SIDs for sheetfed on premium coated paper as measured with a densitometer set to Status "T" are:

Yellow 1.05
Magenta 1.50
Cyan 1.40
Black 1.70

Do you happen to have a resource that would specify standard target SIDs for different types of paper. All of the paper that is run on is uncoated paper.

 

[blazini]

Do you happen to have a resource that would specify standard target SIDs for different types of paper. All of the paper that is run on is uncoated paper.

IMO that all depends on the actual "color" of the ink that you use and how curves are set up between prep and the press. There was a post on here where a bunch of people posted the densities that they use and they were all quite a bit different. You really need to do some testing in your own place.

My offset targets are

Y-.90
M-1.00
C-1.05
K-1.20

coated

Y-90
M-120
C-125
K-160

With matte paper about in the middle.

 

[gordo]

Do you happen to have a resource that would specify standard target SIDs for different types of paper. All of the paper that is run on is uncoated paper.

For uncoated paper the nominal densities are:
K 1.30, C 1.10, M 1.15, Y 0.95

You can download a PDF from Idealliance that has this info here: DEER Printing Guidelines 2011 Poster-DOWNLOAD | IDEAlliance

best, gordo

 

[gordo]

IMO that [SIDs] all depends on the actual "color" of the ink that you use and how curves are set up between prep and the press.

I don't think I agree with that. Solid ink density is an indirect measure of ink film thickness. If, for example, you are using a Magenta ink that is anywhere near the ISO specification for Magenta then a SID of 1.50 will give you an ink film thickness of ~1.5 microns on a #1 paper. Which is where you want to be to have a stable press. Prepress/plate curves are used to align tone reproduction with a standard and do not have an effect on SIDs.

best, gordo

 

[blazini]

I don't think I agree with that. Solid ink density is an indirect measure of ink film thickness. If, for example, you are using a Magenta ink that is anywhere near the ISO specification for Magenta then a SID of 1.50 will give you an ink film thickness of ~1.5 microns on a #1 paper. Which is where you want to be to have a stable press. Prepress/plate curves are used to align tone reproduction with a standard and do not have an effect on SIDs.

best, gordo

So are you suggesting that running densities lower than this is wrong in some way? Or that if you're not running these densities your press is not "stable". Look at the thread "standard ink densities" posted a little while ago in this forum. You will see numbers ranging from mine (the low end) to yours (the high end).

I really don't care for absolutes like that. I really don't know why it varies so much from operation to operation, but if I had to guess I'd say that it has alot to do with drying requirements. Ink film thickness is a big factor in drying . A UV sheetfed press may not have an issue drying at those densities where as on a heatset webpress running those densities would have some real issues. It's not possible that heatset inks are formulated with stronger pigments to reduce the required amount of ink? Maybe instead of using the word color I should have said "strength"

In sheetfeds (and I'm guessing again since I've never worked in sheetfed) it may be preferable to run more of a weaker ink. I know from personal experience that using mixing "ink extender" (kind of like and sometimes actually is varnish) to weaken the ink and running the ink heavier will help alot with ghosting.

 

[sumitgupta008]

color process

color process

This is a wonderful process. The things given are unanimous and needs to be appreciated by everyone.
-----------------------
Print Photos

 

[gordo]

So are you suggesting that running densities lower than this is wrong in some way? Or that if you're not running these densities your press is not "stable". Look at the thread "standard ink densities" posted a little while ago in this forum. You will see numbers ranging from mine (the low end) to yours (the high end).

I really don't care for absolutes like that.[SNIP]

I did not know that you were referring to heatset web rather than sheetfed (you just said "offset")

Your SIDs for gloss coated are:
K-160, C-125, M-120, Y-90

If your target is SWOP then the historical SID targets are:
K 1.60, C 1.30, M 1.40, Y 1.00

So you'd be a touch low on Cyan, but 20 and 10 points low on Magenta and Yellow respectively which can be problematic.

The industry targets for SIDs are not high or for special equipment of UV inks. They are a midpoint target that a typical offset printer should be able to deliver. The values are absolutes only in the sense that they help standardize presswork and allow for proofs to be standardized which in turn helps print buyers and suppliers manage color expectations.

There are several problems associated with running inks too low:
1- Ink water balance is more difficult to maintain which can result in inconsistent color through the run
2 - A loss of trapping efficiency resulting in a loss of color gamut
3 - A loss light filtering efficiency which results in a loss of color gamut
4 - An inability to align presswork with an industry certified proof.

So, yes, in that sense running densities lower than industry targets is "wrong."

In my experience the main reason printers run inks too low is to lower/control dot gains on press. However this is best achieved with plate curves. I also see press operators using stiffer inks or higher pigment load inks to do the same thing (again that's better done with plate curves.)

One explantaion for the variation in SIDs that printers have reported in previous posts might simply be because of poor instrumentation. I.e. Their densitometers are not calibrated, or are reporting inaccurate values. So they might read 1.20 M but a properly calibrated instrument might report 1.40 for the same patch. Instrument variation is the reason why GATF used to sell a Hi-Lo SID target patch. You read the patch where it says, for example, 1.40 and if your densitometer reported 1.20 then you know that whenever you measured 1.20 it was actually 1.40.

When I see SIDs like yours where one color, i.e. M is 20 points lower than the specification and 5 points lower than C when it should be 10 points higher than C - that to me suggests that there is probably a problem with the M press unit (mechanical, temperature, water, ink, paper calcium carbonate etc., etc.)

best, gordo

 

[blazini]

I did not know that you were referring to heatset web rather than sheetfed (you just said "offset")

"offset" meant offset paper.

I'm still not following you here. You assume that I work with one press and it's a 4-color press where I would be running the same inks in the same units. These aren't densities that I came up with. These are "house" densities that every press in the plant conforms to.

If your target is SWOP then the historical SID targets are:
K 1.60, C 1.30, M 1.40, Y 1.00..............


.................One explantaion for the variation in SIDs that printers have reported in previous posts might simply be because of poor instrumentation. I.e. Their densitometers are not calibrated, or are reporting inaccurate values. So they might read 1.20 M but a properly calibrated instrument might report 1.40 for the same patch. Instrument variation is the reason why GATF used to sell a Hi-Lo SID target patch. You read the patch where it says, for example, 1.40 and if your densitometer reported 1.20 then you know that whenever you measured 1.20 it was actually 1.40.

I can assure you that is not the case. My densitometer reads the same (+/-.02) from the 10 others that are sitting on the other presses. Even if my densitometer were totally wacked out my closed loop color reports pretty much the same densities as well.

When I see SIDs like yours where one color, i.e. M is 20 points lower than the specification and 5 points lower than C when it should be 10 points higher than C - that to me suggests that there is probably a problem with the M press unit (mechanical, temperature, water, ink, paper calcium carbonate etc., etc.)

best, gordo

I have no "M unit" I run a KCMY sequence in whatever rotation the job allows. We run 7-unit presses. Today it might be KCMY-PMS-PMS, tomorrow it might be K-PMS-CMY-PMS. These rotations don't affect densities on this 10 year old press, nor do they on the 40 year old press or the 6 month old press. That's another thing, I've had breakdowns and had to run YKCM and have watched the color change. The most noticeable difference is always between the Y and M. While it's usually acceptable, I've seen images running down the circumference go both ways. One is too red the other is too yellow and you have to land in the middle, the only thing that changed here was the rotation.

other than that, possibly it's the screening technique used, which best I can tell is XM. It's not traditional AM, and it's not FM, but I've never actually thought to pick anyones brain about it. I can also say that switching to a different manufacturers ink for a test at the end of a run turned up with completely different color. Pushing the K ink to 2.10 still didn't turn up as "black" as the previous ink at 1.60. I seen similar results with the yellow, and since the only thing that changed was the ink........

 

[gordo]

"offset" meant offset paper.

I'm still not following you here. You assume that I work with one press and it's a 4-color press where I would be running the same inks in the same units. These aren't densities that I came up with. These are "house" densities that every press in the plant conforms to.

I'm just working with the information you're providing. Your house densities are unusual.

I can assure you that is not the case. My densitometer reads the same (+/-.02) from the 10 others that are sitting on the other presses. Even if my densitometer were totally wacked out my closed loop color reports pretty much the same densities as well.

That's good.

I have no "M unit" I run a KCMY sequence in whatever rotation the job allows. We run 7-unit presses. Today it might be KCMY-PMS-PMS, tomorrow it might be K-PMS-CMY-PMS. These rotations don't affect densities on this 10 year old press, nor do they on the 40 year old press or the 6 month old press.

Changing your rotations the way you describe it is also unusual. But not having a dedicated M unit at least eliminates a mechanical problem being the cause of the unusual ink densities that you are running.

That's another thing, I've had breakdowns and had to run YKCM and have watched the color change. The most noticeable difference is always between the Y and M. While it's usually acceptable, I've seen images running down the circumference go both ways. One is too red the other is too yellow and you have to land in the middle, the only thing that changed here was the rotation.

Yes, changing the rotation will change the final color.

other than that, possibly it's the screening technique used, which best I can tell is XM. It's not traditional AM, and it's not FM, but I've never actually thought to pick anyones brain about it.

If the (XM) screening is like Agfa Sublima, Kodak Maxtone, Heidelberg Hybrid, et. al. then it's effectively AM screening. If the screening is run at over 175 lpi and the dot gain is not compensated for via plate curves then than could cause the press operator to reduce SIDs to try and compensate.

I can also say that switching to a different manufacturers ink for a test at the end of a run turned up with completely different color.

Yes. Also changing to a different ink series from the same manufacturer can have the same effect.

Pushing the K ink to 2.10 still didn't turn up as "black" as the previous ink at 1.60. I seen similar results with the yellow, and since the only thing that changed was the ink........

A densitometer simply measures the amount of light being reflected from a sample. As ink film thickness increases less light is reflected back and so the density reading goes up. At a certain point there is no increase in the density reading. With Black ink that happens at about a density reading of 2.7.

So it's strange that a density of 2.10 wouldn't appear blacker than at 1.60. Even if the inks were different.
If two different black inks are run to the same SID it is quite possible that one would appear "blacker." That is usually caused by a difference in the hue of the ink - a bluer black will appear blacker than a browner black. But if they are at the same SID then they are reflecting the same amount of light therefore they are the same darkness.

best, gordo

 

[blazini]

I'm just working with the information you're providing. Your house densities are unusual.

If by unusual meaning it doesn't meet SWOP targets, then I guess you are right, but like I said the thread pertaining to ink densities would have you think that even SWOP is unusual, though I don't think anyone mentioned the type of printing they were doing.

Changing your rotations the way you describe it is also unusual.

Yes but sometimes it's necessary. Once in a while I will run a PMS with a K screen that must print before it. I also run metallics that need to be run last or it will sensitize plates in the units after it. I even run MICR once in a while that must run last because of blanket take-off.

I'm just working with the information you're providing. Your house densities are unusual.



That's good.



Changing your rotations the way you describe it is also unusual. But not having a dedicated M unit at least eliminates a mechanical problem being the cause of the unusual ink densities that you are running.



Yes, changing the rotation will change the final color.



If the (XM) screening is like Agfa Sublima, Kodak Maxtone, Heidelberg Hybrid, et. al. then it's effectively AM screening. If the screening is run at over 175 lpi and the dot gain is not compensated for via plate curves then than could cause the press operator to reduce SIDs to try and compensate.



Yes. Also changing to a different ink series from the same manufacturer can have the same effect............


............If two different black inks are run to the same SID it is quite possible that one would appear "blacker." That is usually caused by a difference in the hue of the ink - a bluer black will appear blacker than a browner black. But if they are at the same SID then they are reflecting the same amount of light therefore they are the same darkness.

I am aware of the difference between a brown-black and a blue-black but this was more of like a not so black-black. It was the manufacturer's process black but compared to our standard black it was more towards dark grey.

I realize that you're much more of an "expert" on the subject than I am but you actually stated most of the reasons why you would run away from standards. For example depending on the type of machine (age. condition) maybe running a higher pigmented ink at lower densities will give you a sharper dot, pretty much what you said in different words. I can't think of all the reasons you would want to deviate from standards but I can say that it can be done with plenty of stability

 

[gordo]

If by unusual meaning it doesn't meet SWOP targets, then I guess you are right, but like I said the thread pertaining to ink densities would have you think that even SWOP is unusual, though I don't think anyone mentioned the type of printing they were doing.

No, it's not unusual because it doesn't meet SWOP targets (unless your goal is to align presswork to a SWOP proof). It's unusual because you run a CM sequence (which is pretty standard). What's unusual is that your M SID is less than your C. The reason that ISO, SWOP etc. run M at a higher SID than C with a CM sequence is to improve overprint trapping since in a KCMY sequence C is trapping to to basically dry paper whereas M is trapping to wet ink (C). All things being equal, running M at a lower SID than C affects the hue and saturation of blues making them more Cyany and lower than their potential saturation. Now, if the sequence was KMCY instead, then running the M at a lower SID than C would seem to make more sense.

For example depending on the type of machine (age. condition) maybe running a higher pigmented ink at lower densities will give you a sharper dot, pretty much what you said in different words. I can't think of all the reasons you would want to deviate from standards but I can say that it can be done with plenty of stability

You don't really run higher pigmented ink at lower densities. You actually run them at the same density. However, at that same density, the higher pigmented ink results in a thinner film of ink. Yes, you can deviate from standards and run stable. That being said, offset lithography is a mechanical process that only works within a fairly narrow range. If your ink film is too thin (or too thick) you run the risk of experiencing all kinds of problems on press. The standard SIDs were established as being achievable for a press in reasonable (not perfect) mechanical condition. If they weren't then they couldn't be a standard.
When a press deviates from that standard, particularly going to lower SIDs or when SIDs are switched around (as in your case), then, IMHO there should be a very good reason as to why otherwise the potential consequences could eliminate any desired benefit.

I'll give you a quick example. I was at a sheetfed shop that was running one of the original GRACoL7/G7 characterization tests. There was no proof and they were having a very difficult time hitting the GRACoL numbers. The sheet had an overall red cast. I asked the press operator if they had any trouble matching their proofs. No he said. So I asked prepress to pull a proof of the test form. The proof did not have a red cast. Then I noticed the ink sequence. Here's a photo of what I saw:

The ink sequence was KMCY. So I asked why the KMCY sequence and after much discussion it turned out that they had switched C and M to solve a problem with purples that they had on a job a few months previously. They had never switched back. And although the press operator told me he wasn't having trouble matching their proofs...in fact their makeready times were significantly longer with more waste. In fact they were having all kinds of problems matching their proofs. They assumed it was a prepress problem - but like many shops pressroom and prepress weren't on good speaking terms.

So I asked him to switch back to a KCMY sequence and the numbers and colors all fell into place. (I was told by one of the GRACoL committee guys that the ink sequence wouldn't affect the colors and numbers - but that's another story.)

I'm not saying that's the case at your shop, or that what you are doing is wrong. But it is unusual.

best, gordo

 

[blazini]

I'm not saying that's the case at your shop, or that what you are doing is wrong. But it is unusual.

best, gordo

Oh I have trouble matching proofs all the time. If I go anywhere with the densities I posted for colrmatch it's generally lower. I also have to get Y plates cut back (screen values) pretty often. Honestly it's just the nature of the beast, there are several presses of each cutoff and jobs get shuffled around each press on that cutoff. Jobs are often yanked off one press halfway through and put on another later on. It's pretty difficult to match a modern press to an older one, especially since my press is plated at a higher line screen than the others. I'm sure you can really finetune prepress in a shop that runs 1 or 2 presses but I think it only gets so good under these circumstance (although I'm sure it could be better)

 

[gordo]

In shops that have multiple presses i.e. more than 2 there is usually someone with a title like Technical Director, Quality Manager, Manufacturing Manager, etc. who, among other duties, would be to bring the presswork into alignment both to the proof as well as across presses. It's certainly doable but does require someone to take charge and make it happen.

best, gordo