Grey balance test

[Alois Senefelder]

Enlightenment!

Enlightenment!

Erik and fellow Lithographers,

"Water just affects the delivery rate of Ink into the system" I also disagree.


1) The Primary Function of F.S. is to keep the Non-Image Areas clean and replenish the

Desensitized Properties of the plate.

2) Maintain Thin Film of Water on Plate, the dampening system applies a continuous

sheet of F.S. Approx. 0.4 microns thick, the width of the press and travelling at press speed.

3) On the Press Inking Train, Ink and Fountain Solution in conjunction is required to form a

Stable Micro Emulsion ( Ink/Water Balance)

4) Crucial, the formation of the correct Ink/Water Balance Emulsion will -

Never Keep the Plate Clean


Regards, Alois

 

[Deleted member 16349]

That seems conservative to me. I would say the true thickness range would be closer to twice that, but I’ll conceed the point. Even with a range of +/- 0.30, that’s still a rather wide window.

I think you have misinterpreted this. It does not mean that the range of +/- 0.30 is the range of acceptable printing. I think you need to look at what change in ink film is required to obtain a more acceptable density tolerance of say +/-0.05.

If +/- 0.30 has the total range of 0.60 density points over a total ink film range of 0.25 (1.25 - 1.0) then the density tolerance of +/-0.05 or total range of 0.10 will require a total ink film range of 0.1/0.60 x 0.25 = 0.042.

This would mean 1 micron to 1.042 microns or a 4.2 % change in ink film for the total range is required to meet the desired tolerance range.. That would be a +/- 2.1 % change in ink film. That is tight and in my opinion, Gordon does not have the right data. Hopefully he can clarify this.

You seem to realize this when you said that you think the ink film result would be twice the stated amount. Don't concede that point too early.

 

[Alois Senefelder]

**********

**********

Gentlemen and fellow Lithographers,

The "Hot" topic - Ink Film Thickness and Ink Density.

Hopefully the PDFs will shed a lttle enlightenment !




Regards, Alois

 

[gordo]

Gordon, can you clarify this range a bit. It does not look right to me.

Does the statement mean that with a range of 0.25 microns (from 1 to 1.25 microns) of ink film, one would have a range of 0.60 (+/- 0.30 ) density points? This would imply a fairly narrow range but I don't think the stated ranges are correct.

It would be good if we all understand what the real ranges are. My view being that the range for ink is wide with respect to the density tolerance range. You feel that it is narrow and it might be due to wrong data.

This is going a bit off topic but...

Below is a chart showing the relationship of SIDs and ink film thickness in microns. It was published by Heidelberg in one of their educational books.



The left chart is the original. The right is of presswork run at maximum SIDs (to increase gamut).

The data may be wrong or I may be misunderstanding the chart. You would know better than me.

If the ink film thickness is too thin then it over-emulsifies and breaks down. If it's too thick then the ink starts to "tail" (mist). I've done a lot of work at high SIDs but never saw any reason to try low SIDs.

The chart suggest to me that a .05 SID shift results in an ink film shift of about .05 microns. As a tolerance standard that seems like a very narrow window for a 40" offset press running 10,000 impressions an hour.

The DMaxx SIDs in the right side chart are what I used to run when printing at high SIDs for increased gamut. The typical max SID was about .30 above industry standard. That still gave one some room for SID variations before ink tailing would appear.

Perhaps you could clarify?

HAH! Alois posted at the same time with a similar chart. But with a tad more info.

gordo

 

[Deleted member 16349]

The left chart is the original. The right is of presswork run at maximum SIDs (to increase gamut).

The data may be wrong or I may be misunderstanding the chart. You would know better than me.

If the ink film thickness is too thin then it over-emulsifies and breaks down. If it's too thick then the ink starts to "tail" (mist). I've done a lot of work at high SIDs but never saw any reason to try low SIDs.

The chart suggest to me that a .05 SID shift results in an ink film shift of about .05 microns. As a tolerance standard that seems like a very narrow window for a 40" offset press running 10,000 impressions an hour.

The DMaxx SIDs in the right side chart are what I used to run when printing at high SIDs for increased gamut. The typical max SID was about .30 above industry standard. That still gave one some room for SID variations before ink tailing would appear.

Perhaps you could clarify?

HAH! Alois posted at the same time with a similar chart. But with a tad more info.

gordo

I don't have any problem with these plots. They describe inks (probably sheetfed inks) that are a little stronger than what I was used to (web EB inks) and very much stronger than what you will find with newspaper inks.

In your earlier post, you stated +/- 0.30 density points and I think from looking at the plots it should have been just 0.30 density points for the whole range from 1 to 1.25 microns. That makes sense. Of course it is slightly different depending on which ink is being looked at. Yellow is weaker than black with respect to the change in density with the change in ink film.

I know you see this as a narrow window but I look at it differently. If the ink feed system is a pump, having a pump that has variation of +/- 5% is not such a great pump. It would not be considered has being very accurate. One can have a pump deliver in the +/-1% range and even less. Look at the plot and one can imaging what that will do to the variation of density. In this context I am speaking about the average steady state density and not the variations about the average.

 

[rich apollo]

Rich, I had a look at Andrew's web site and found some of his patent info. At this time, I don't see that it is anything special but I could be wrong. The site does not really say much about what the concept does in any detail. It for sure is not in a direction I would like things to go.

He has developed a colorbar that has limited single color patches, it is primarily 3c gray and K screens. The bars are constructed such that not only can you monitor gray balance, but you can see registration issues. Techkon can read the bar in their Expresso software to give feedback.

He also has a system to control the ink feed from this data.

He runs a print shop in Hong Kong. He is using this system for live production work. I found his samples to be quite compelling.

 

[Deleted member 16349]

He has developed a colorbar that has limited single color patches, it is primarily 3c gray and K screens. The bars are constructed such that not only can you monitor gray balance, but you can see registration issues. Techkon can read the bar in their Expresso software to give feedback.

He also has a system to control the ink feed from this data.

He runs a print shop in Hong Kong. He is using this system for live production work. I found his samples to be quite compelling.

Rich, thanks for the added information but it does not change my view. Andrew's method still aims to use patches for feedback. My thinking is to avoid the need for feedback by making the process inherently consistent and predictable.

I think in terms of what changes the process needs to be able to have no colour patches. So looking at some new method to have colour patches for me is going backwards and not forwards in any effort to innovate.

 

[gordo]

Rich, thanks for the added information but it does not change my view. Andrew's method still aims to use patches for feedback. My thinking is to avoid the need for feedback by making the process inherently consistent and predictable.

I think in terms of what changes the process needs to be able to have no colour patches. So looking at some new method to have colour patches for me is going backwards and not forwards in any effort to innovate.

Quite right. It is technically doable to use the live image area to confirm and monitor presswork and thereby eliminate color bars. It's also doable to close the loop so that the system (from input art to presswork) to "learn" and thereby automatically fine tune individual parameters over time. I developed the prototype and did feasibility studies for such a system at Creo back in 2000 (Project Janus). Some of that thinking is embodied in the Kodak Colorflow solution.

There are a many additional benefits to eliminating color bars and working off the live image area instead. For example, it is possible to identify and tolerance areas of critical color match and also allow the press operator to know not only that a match has, or has not been made, but also whether the data on the plate in a given print condition allows him to achieve the match. It also enables remote press approvals.

best, gordo

 

[Lukas Engqvist]

When varying the SID this much how is the print contrast affected? I understood the place to target SID is where the contrast reaches a plateau.

 

[Deleted member 16349]

Quite right. It is technically doable to use the live image area to confirm and monitor presswork and thereby eliminate color bars. It's also doable to close the loop so that the system (from input art to presswork) to "learn" and thereby automatically fine tune individual parameters over time. I developed the prototype and did feasibility studies for such a system at Creo back in 2000 (Project Janus). Some of that thinking is embodied in the Kodak Colorflow solution.

There are a many additional benefits to eliminating color bars and working off the live image area instead. For example, it is possible to identify and tolerance areas of critical color match and also allow the press operator to know not only that a match has, or has not been made, but also whether the data on the plate in a given print condition allows him to achieve the match. It also enables remote press approvals.

best, gordo

Trying to use the live image is one approach and is now being tried by QuadTech and some others but what I envision is to have it all predetermined so there is not need to have the feedback even in the live area.

Lots of interesting approaches should be tried to move things forward. There needs to be more effort in trying new ideas out, even if many may ultimately fall short of the desired goal. That is the only way to find out what the rules really are and what will work best. Theorize, test and innovate.

 

[gordo]

When varying the SID this much how is the print contrast affected? I understood the place to target SID is where the contrast reaches a plateau.

Print contrast is calculated by measuring the ink density of a solid area and the ink density in a 75% tint. You build a tone reproduction compensation curve for the higher SIDs and that takes care of print contrast.

best, gordo

 

[gordo]

Trying to use the live image is one approach and is now being tried by QuadTech and some others but what I envision is to have it all predetermined so there is not need to have the feedback even in the live area.

The use of the live image area is to confirm the color (mitigates litigation) as well as provide data feedback to the system so that predetermination can happen.

Lots of interesting approaches should be tried to move things forward. There needs to be more effort in trying new ideas out, even if many may ultimately fall short of the desired goal. That is the only way to find out what the rules really are and what will work best. Theorize, test and innovate.

I don't believe there are any "skunk works" in the printing industry. I don't know about other graphic arts vendors but at Creo, any proposal for the development of new technologies first had to be vetted for economic feasibility. I.e. what resources would be needed over what period of time to bring to market, would the sell price deliver the required profit margin, is there a market for the solution, what is the competitive landscape, etc, etc. Afterall, as with any company - resources are limited. That process tended to weed out a great many ideas that ultimately may have been worth pursuing.
Creo did have a policy of selecting an engineer each year who would be given free range to develop their ideas without the usual restrictions. One is better than none I guess.

gordo

 

[Deleted member 16349]

The use of the live image area is to confirm the color (mitigates litigation) as well as provide data feedback to the system so that predetermination can happen.



I don't believe there are any "skunk works" in the printing industry. I don't know about other graphic arts vendors but at Creo, any proposal for the development of new technologies first had to be vetted for economic feasibility. I.e. what resources would be needed over what period of time to bring to market, would the sell price deliver the required profit margin, is there a market for the solution, what is the competitive landscape, etc, etc. Afterall, as with any company - resources are limited. That process tended to weed out a great many ideas that ultimately may have been worth pursuing.
Creo did have a policy of selecting an engineer each year who would be given free range to develop their ideas without the usual restrictions. One is better than none I guess.

gordo

Part of the predetermination process would be the proper mapping of how the press prints. I believe this is not done well enough now. I don't think any feedback to prepress should be done with live jobs.

Your point about litigation is valid but if there is very little variation and the target is reproduced, it does not have to be done at the press but can be done forensically at any time. What usually happens in manufacturing is that proven consistent performance leads to less need for confirmation.

True, I don't think there are too many skunk works going on either but there should be. One reason I am so big on developing theory is because it is a low cost approach. Not everyone can do that kind of work but it can be done. I have been doing it with little cost for many years. It leads to many possible and practical options. A theoretical approach also is a frame work for determining what questions need to be asked and what problems need to be understood.

With the existing development methods used, it is a hodgepodge of trial and error with little structure on what needs to be done to get to a desired goal. Developing and testing technologies that are not based on valid and comprehensive theory is a recipe for the waste of resources and time. It is no surprise that companies want to avoid the costly historical development failure experiences that this industry has experienced.

Of course my goal is to try to change that trend by getting a press manufacture interested in new possibilities that cost less. In order to get the whole process moving in a direction where it can be inherently consistent and predetermined, the effort at the press is required first.

 

[Green Printer]

All of this software and it variations have been around for years along with the profiling. These profiles work great until a pressroom supplier changes something and doesn't tell you. When this happens it usually gets blamed on the prepress for changing something. So you will piss time away trying to track it down.
Until you know that your pressroom consumables are the SAME with each batch it ends up a war between the pressroom and prepress.
To make these systems work on a continuing basis you need assurance that you pressroom supplies have not changed.
For the large printer when you decide on a pressroom supplier keep retains from the batch that you have picked.
Have the retains spectral analyzed, this is your standard. If you encounter problems with new batches have them analyzed the new better match your retain. If they are different you will not be able to match your standard. The Solution is reject and have your supplier replace it with what you have ordered.
After a few times of this your supplier will get his act together or no longer be a supplier.

 

[meddington]

The left chart is the original. The right is of presswork run at maximum SIDs (to increase gamut).

These charts seem to be showing a typical aim point for "normal" and "Dmaxx" Sids, but not necessarily an operational/mechanical range of ink film thickness (from over-emulsification to misting).

Alois's chart shows the ink film range customarily used, 0.7-1.1 µm. This range appears to be taken from ISO 2846-1, which is used to determine color and transparency of 4/c litho inks, but uses a laboratory printability tester, rather than a true litho press. I haven't any true data, other than to say that I've seen magenta printed with target aims points anywhere from 1.2 to 1.7 on coated #2 paper with no operational issues, but this is hardly scientific, and of course the same ink film could yield different densities on different substrates. I think one might have to perform their own test to determine a conclusive operational range.

Sorry, I know its off topic, but still interesting.

 

[Deleted member 16349]

These charts seem to be showing a typical aim point for "normal" and "Dmaxx" Sids, but not necessarily an operational/mechanical range of ink film thickness (from over-emulsification to misting).

Alois's chart shows the ink film range customarily used, 0.7-1.1 µm. This range appears to be taken from ISO 2846-1, which is used to determine color and transparency of 4/c litho inks, but uses a laboratory printability tester, rather than a true litho press. I haven't any true data, other than to say that I've seen magenta printed with target aims points anywhere from 1.2 to 1.7 on coated #2 paper with no operational issues, but this is hardly scientific, and of course the same ink film could yield different densities on different substrates. I think one might have to perform their own test to determine a conclusive operational range.

Sorry, I know its off topic, but still interesting.

Actually the term ink film thickness is misleading because the ink film can have water in it too. It is better to think in terms of the amount of ink pigment in the ink film when looking at such curves.

I have done tests on press with a positive ink feed method and there is a close correlation with the ink feed rate and the change in density. One can plot these curves on press when one has a positive ink feed. It is basically independent of water feed. With a positive ink feed, one can make predictable changes in density from one level to another based on the curve data.

The goal in the process is not to try and control the ink film thickness but the amount of pigment in the ink film. This is done by the controlled feed rate of fresh ink.

 

[Green Printer]

The goal in the process is not to try and control the ink film thickness but the amount of pigment in the ink film. This is done by the controlled feed rate of fresh ink.

You have got to be kidding "The amount of pigment in the ink film is controlled by the feed rate of fresh ink." How are you going to vary the pigment load by changing the feed rate. The pigment load of an ink is a constant. How do you get more pigment to transfer?

 

[Lukas Engqvist]

Print contrast is calculated by measuring the ink density of a solid area and the ink density in a 75% tint. You build a tone reproduction compensation curve for the higher SIDs and that takes care of print contrast.

best, gordo

Yes I know that part. But for a given dot gain curve a change in SID will change that contrast. If I set the wanted dot gain for a standard SID, then there is an increase in density by 0.5 won't that also affect the contrast? That is why when finding a target SID I would try to aim for one where the LAB are as close to standard as possible, AND where a variation (that ideally should be as small as possible) will not result in a big change in contrast. The change in contrast (or dot gain) caused by a variation in density as I understand is what affects the colour balance of the CMY patches most (Not the full tone density, or even the trapping).

(I can't change the compensation curve while running a print job or a test chart… can I?)

 

[Deleted member 16349]

You have got to be kidding "The amount of pigment in the ink film is controlled by the feed rate of fresh ink." How are you going to vary the pigment load by changing the feed rate. The pigment load of an ink is a constant. How do you get more pigment to transfer?

Sorry you can't understand this.

 

[Stephen Marsh]

PShop is set to its default "North America General Purpose 2" That is used by the newspaper editorial and, as far as I can tell, also by the agencies that supply ads to the paper. Everyone seems to be using PShop 5.

Hi Gordo,

So presuming that they convert to CMYK or softproof RGB to CMYK, then the newspaper staff and suppliers to the newspaper are all converting to a web-fed magazine profile that uses 300% total ink and a lower dot gain - rather than using a Newspaper colour setting and a newspaper profile that would deliver a lower total ink limit and a higher dot gain. This sounds about right* for many “professionals” in our industry [*of course by right, I mean totally wrong :]

I have yet to meet a designer or ad agency that has changed their PShop’s default color settings.

An all too common scenario, which is a very sad reflection on the levels of professionalism and knowledge in our industry.

My understanding is that if PShop is left to its default settings then the profile that’s used to convert RGB to CMYK uses “medium” GCR.

The old Photoshop 5 (not CS5) or earlier CMYK colour table settings did indeed use Medium GCR as the default method. I am not sure if the ICC profile based methods used in later versions of Photoshop used a “medium” GCR method or not. Medium GCR is a rather arbitrary meaning, however it is safe to presume that the GCR ratio is somewhere between “light”, “Heavy” and “Maximum” GCR ratios.

All incoming art, in this workflow, is run through Binuscan to optimize the images, apply proprietary heavy GCR, and dot gain compensation curves.

I roughly know what this means, but what does this mean for the specifics? I am just curious…

* If the content is RGB, does it honour the RGB profile (if present) or does it ignore tagged profiles and assumes a preset RGB input condition? Or is the workflow CMYK only and all RGB is converted to SWOP CMYK first?

* If the content is CMYK, does it honour the CMYK profile (if present) or does it ignore tagged profiles and assumes a preset CMYK input condition? Is the system setup to expect all incoming CMYK work is SWOP, and then to convert from SWOP to the house CMYK newsprint condition? What would happen if somebody knew better and supplied a CMYK file setup as IFRA or SNAP newsprint, rather than SWOP?


Best,

Stephen Marsh