Dot gain / TVI variation...

[tribay]

Software control

Software control

A program like Alwan Print Optimizer can point out differences wiithin a run and on a run to run basis. It has the ability to adjust the plate curves to how the press is printing and
works with your color bars and sheet readers.

 

[The Heidelberg Guy]

Gordon Gordon Gordon,

After all these years, you still don't understand my philosophy on these issues.
Very sad. :-(

Sure one could have technology to inspect and compare all these points in the image relative to the target. Yes it is already here. I am not advocating using such technology. Basically I do not want to have to measure for control. Measure for calibration but not so much for control. Make the process consistent and predictable and then there would be no need to measure for control.

Just because one would have a standard that asks for the matching of points in the images that does not mean that one has to have active control via measurements. If a capable process, that is calibrated, demonstrates that it continually meets a standard of performance, then one does not have to measure it to confirm it each time. It will become accepted by the customer.

Heidelberg's use of image control at the press was not a great thing at all. It is a technology to compensate for not being able to print consistently within the image. Heidelberg's system could not change an area in the print in the image independently of other parts of the image. You pick an area of concern, the system would look at it and compare it with a reference. Then ink keys would be adjusted to satisfy the match in that area but at the expense of other parts of the image in line with that area.

They would never consider putting such a system on the Anicolor press since there is more consistency with the inking of the plate in all areas. Also this consistent inking of the plate means that the profile for the Anicolor press is more predictable.

I would say the standards organizations are damaging the industry for exactly the reason you stated. It is in their interest to do what they do. Now they also seem to be pulling RIT into the mix. Not a good trend IMO. The universities should be independent so that they can have an independent voice. Although I am not sure they are imaginative enough to know what is wrong. I don't think they have done such a great job in this area. Much of the time they act like users of technology and not fundamental researchers of knowledge.

Your statement "Make the process consistent and predictable and then there would be no need to measure for control" in the real world, is not possible. There are too many factors that provide us with proof that this would not work. Every entity that goes into the printing process has the potential to be controlled, but in itself cannot be controlled without certain mechanical, electrical or chemical technology.

"Heidelberg's use of image control at the press was not a great thing at all. It is a technology to compensate for not being able to print consistently within the image"

The Image Control is a great tool! It is being able to properly use these functions to assist the operator in calibrations, production runs and color adjustment.

I’ll use the Anicolor for example. I have instructed many new Anicolor machines, they are very nice and efficient machines. They may not have the color swing that conventional offset machines do, but they also have a downfall....temperature. If the temperature is not maintained, the press sheets cannot be sold to the customer.

So, without the Image Control or some other measuring devise, you will probably have a DeltaE of 5 to 6 throughout the run with a very good pressman. Without a chilling devise on the Anicolor, we have no control at all.

Either way, we rely on something to help us control print.

 

[J]

[SNIP]
So, without the Image Control or some other measuring devise, you will probably have a DeltaE of 5 to 6 throughout the run with a very good pressman.

Could you explain exactly what is meant by "a DeltaE of 5 to 6 throughout the run"? What is being measured? What is being compared?

J

 

[The Heidelberg Guy]

Could you explain exactly what is meant by "a DeltaE of 5 to 6 throughout the run"? What is being measured? What is being compared?

J

DeltaE is a measurement from the reference (color, OK sheet ect.) to the current measurement.

For instance; A customer OK sheet has a DeltaE of 0, we measure the press sheets to ensure the job stays as close as possible to the OK sheet, DeltaE 0. Commonly, a good run will constitute a DeltaE of 0.8 average. If a sheet has a DeltaE of 2, it is commercially acceptable in most shops in the US, whereas the DeltaE of 5 to 6 is grossly out of the ballpark in all.

Hope I answered your question.

Tim

 

[Deleted member 16349]

Your statement "Make the process consistent and predictable and then there would be no need to measure for control" in the real world, is not possible.

Sorry but you are wrong. You have experience with mainly conventional press design concepts which makes it difficult for you to predict what is possible with different concepts.

How can you say what is possible when every Heidelberg press does not have control of the ink that is delivered to the roller train? No mechanical device on those presses is directly related to the amount of ink that goes into the roller train.

But it was of interest to hear that temperature affects the Anicolor so much. It just confirms my view of that press. Thanks.

 

[The Heidelberg Guy]

Sorry but you are wrong. You have experience with mainly conventional press design concepts which makes it difficult for you to predict what is possible with different concepts.

How can you say what is possible when every Heidelberg press does not have control of the ink that is delivered to the roller train? No mechanical device on those presses is directly related to the amount of ink that goes into the roller train.QUOTE]

Im speaking for any printing press. If I am reading you right, you are stating "Basically I do not want to have to measure for control. Measure for calibration but not so much for control. Make the process consistent and predictable and then there would be no need to measure for control."

As I said above, "So, without the Image Control or some other measuring devise, you will probably have a DeltaE of 5 to 6 throughout the run with a very good pressman. Without a chilling devise on the Anicolor, we have no control at all." meaning control has to come from somewhere, be it the pressman, materials or a device of some kind.

 

[Deleted member 16349]

Im speaking for any printing press. If I am reading you right, you are stating "Basically I do not want to have to measure for control. Measure for calibration but not so much for control. Make the process consistent and predictable and then there would be no need to measure for control."

As I said above, "So, without the Image Control or some other measuring devise, you will probably have a DeltaE of 5 to 6 throughout the run with a very good pressman. Without a chilling devise on the Anicolor, we have no control at all." meaning control has to come from somewhere, be it the pressman, materials or a device of some kind.[/QUOTE]

If you make a process inherently consistent then you don't need control. I agree with you that conventional presses and the Anicolor press need controls of some kind because they are not inherently consistent by design.

A press can be made to be inherently consistent by design. When that is done there will be low variation in colour through the run and without the need for the operator to make any ink adjustments.

I can be difficult to believe this since there are no presses on the market yet that have this capability but it can be done.

It is not a difficult technical problem but is a huge cultural problem in the industry. Since people don't believe it is possible, they then don't think of how to make it possible.

 

[The Heidelberg Guy]

Im speaking for any printing press. If I am reading you right, you are stating "Basically I do not want to have to measure for control. Measure for calibration but not so much for control. Make the process consistent and predictable and then there would be no need to measure for control."

As I said above, "So, without the Image Control or some other measuring devise, you will probably have a DeltaE of 5 to 6 throughout the run with a very good pressman. Without a chilling devise on the Anicolor, we have no control at all." meaning control has to come from somewhere, be it the pressman, materials or a device of some kind.

If you make a process inherently consistent then you don't need control. I agree with you that conventional presses and the Anicolor press need controls of some kind because they are not inherently consistent by design.

A press can be made to be inherently consistent by design. When that is done there will be low variation in colour through the run and without the need for the operator to make any ink adjustments.

I can be difficult to believe this since there are no presses on the market yet that have this capability but it can be done.

It is not a difficult technical problem but is a huge cultural problem in the industry. Since people don't believe it is possible, they then don't think of how to make it possible.[/QUOTE]

I like the way you think Erik! I really think its good to think outside the box, something good always comes from it!

 

[danremaley]

Dot gain changes

Dot gain changes

Thought I'd share what Felix Brunner thinks of color control. I am in System Brunner's Camp, he knows more about color printing than anyone alive or dead! He contends that 80% of print problems are dot related - 20% SID. "What do you measure."
See Attached:
Dan Remaley
412.889.7643

 

[Deleted member 16349]

I

I like the way you think Erik! I really think its good to think outside the box, something good always comes from it!

Thanks. I really really hope that it won't take so long to have that capability demonstrated to all. It potentially can give offset a well needed boost in its fight with digital printing presses. Long live offset!

 

[The Heidelberg Guy]

Thought I'd share what Felix Brunner thinks of color control. I am in System Brunner's Camp, he knows more about color printing than anyone alive or dead! He contends that 80% of print problems are dot related - 20% SID. "What do you measure."
See Attached:
Dan Remaley
412.889.7643

I have to agree 100% I would say his estimate of 80% is right on the money! Learn all you can from him!

 

[The Heidelberg Guy]

Thanks. I really really hope that it won't take so long to have that capability demonstrated to all. It potentially can give offset a well needed boost in its fight with digital printing presses. Long live offset!

Looking for the can of worms, I have an opener LOL

 

[J]

DeltaE is a measurement from the reference (color, OK sheet ect.) to the current measurement.

For instance; A customer OK sheet has a DeltaE of 0, we measure the press sheets to ensure the job stays as close as possible to the OK sheet, DeltaE 0. Commonly, a good run will constitute a DeltaE of 0.8 average. If a sheet has a DeltaE of 2, it is commercially acceptable in most shops in the US, whereas the DeltaE of 5 to 6 is grossly out of the ballpark in all.

Hope I answered your question.

Not quite. When you say you're measuring the press sheets - what exactly are you measuring and summing up with one DeltaE number? Are you measuring the solid ink patches and averaging them? The solids and RGB over prints and averaging them?

J

 

[gordo]

Thought I'd share what Felix Brunner thinks of color control. I am in System Brunner's Camp, he knows more about color printing than anyone alive or dead! He contends that 80% of print problems are dot related - 20% SID.

He's wrong. 80% of print problems are customer related.

best, gordo

 

[The Heidelberg Guy]

Not quite. When you say you're measuring the press sheets - what exactly are you measuring and summing up with one DeltaE number? Are you measuring the solid ink patches and averaging them? The solids and RGB over prints and averaging them?

J

With Image control, you can read image or the color control strip, so I am using that as an example. The DeltaE can be read as an average of all or one ink zone. The example I was refering to is an average of all ink zones.

 

[J]

With Image control, you can read image or the color control strip, so I am using that as an example. The DeltaE can be read as an average of all or one ink zone. The example I was refering to is an average of all ink zones.

I don't mean to be pedantic, but terms like a "DeltaE of 5 to 6 throughout the run" get used by several people in their posts with out explanation. I'm just trying to make sure that I clearly understand what is meant.

So, you are measuring all the CMYK and RGB patches in the color bar of your OK sheet, then you measure the same patches on a subsequent sheet, average the DeltaEs compared with the OK sheet to come up with the final DeltaE of 5 to 6. Correct?

And you also have the ability to scan the live image area of the press sheet and average the total DeltaEs of the live image area of the subsequent sheets compared with the OK sheet. Correct?
If that is correct, can you compare only certain sections of the live image area rather than the total live image area to get your average DeltaE?

thanks for your patience, J

 

[The Heidelberg Guy]

I don't mean to be pedantic, but terms like a "DeltaE of 5 to 6 throughout the run" get used by several people in their posts with out explanation. I'm just trying to make sure that I clearly understand what is meant. No problem!

So, you are measuring all the CMYK and RGB patches in the color bar of your OK sheet, then you measure the same patches on a subsequent sheet, average the DeltaEs compared with the OK sheet to come up with the final DeltaE of 5 to 6. Correct? Yes

And you also have the ability to scan the live image area of the press sheet and average the total DeltaEs of the live image area of the subsequent sheets compared with the OK sheet. Correct? Yes
If that is correct, can you compare only certain sections of the live image area rather than the total live image area to get your average DeltaE? Yes

thanks for your patience, J Your welcome!

 

[naltius]

Dot gain (black)

Dot gain (black)

Hi, I have a problem with dot gain of black, it is around 17-18 percent, while other colors dot gain is much much smaller.
In what could be the problem?
Thank you in advance.

 

[Lukas Engqvist]

According to ISO coated normally CMY is 2% less than K.