ISO Ink density

[gordo]

After reading ur opinions I found dat there is no ISO Ink density, But there are standerd LAB.

So can u plzz tell me wat are the standerd LAB valu for CMYK?

You should buy a copy of the ISO standard so that you have all the information that you need rather than just bits and pieces. I'm sure that once you've read it through you'll have many more questions.

best, gordon p

 

[pacificiam]

Okey Gordon

thnks

 

[Stephen Marsh]

Im very thankful to all of u to share ur knowledge with me.
After reading ur opinions I found dat there is no ISO Ink density, But there are standerd LAB.

So can u plzz tell me wat are the standerd LAB valu for CMYK?

I am a little bit late to the party!

Fogra 39 Lab values for proofing solid primaries (not sure if presswork differs) -

C = L*55 a*-37 b*-50
M = L*48 a*74 b*-3
Y = L*89 a*-5 b*-93
K = L*16 a*0 b*0

+/- 5 dE76


Regards,

Stephen Marsh

 

[Disappointed]

For press work, the LAB values are established on-press by running ink to the lowest delta-E reading possible. That should then define the LAB values for that paper / ink combination.

Not all inks will achieve ISO values and this will become apparent when very high delta-E values are seen.

 

[meddington]

For press work, the LAB values are established on-press by running ink to the lowest delta-E reading possible. That should then define the LAB values for that paper / ink combination.

Lowest delta E may not always produce the best possible match to the ISO targets, depending on the ink and paper used, and how far they deviate from the standard. Best to target the individual L*, a* or b* values for each ink. For Yellow, the b* value may be more important than the overall delta E value for example, particularly for a not-so-bright substrate. You may also want to pay attention to the secondary overprints. (red, green & blue) while adjusting the primaries. Often there is a compromise to be made.

 

[Disappointed]

I was merely stating how we were taught to profile our system, clearly there are other ways to achieve the same goal.

 

[Deleted member 16349]

Lowest delta E may not always produce the best possible match to the ISO targets, depending on the ink and paper used, and how far they deviate from the standard. Best to target the individual L*, a* or b* values for each ink. For Yellow, the b* value may be more important than the overall delta E value for example, particularly for a not-so-bright substrate. You may also want to pay attention to the secondary overprints. (red, green & blue) while adjusting the primaries. Often there is a compromise to be made.

In general I find the logic behind the present day colour management approach to be quite questionable.

By having these standard colour targets for inks etc., which are not obtainable in practice, the approach accepts that one will have errors right at the start. The idea that systemic errors are acceptable is very strange to me.

But the acceptance of systemic and process errors has been a long working practice in printing. The view that seems to be common in the industry that some perceived small errors are not important is a trap because when one adds up all the errors in the methods, it results in unpredictable results.

People have to work with the methods that they are now given but I hope there is some realization that these methods are not sound otherwise the industry will not get pushed to correct the situation.

 

[Disappointed]

I find it works very well, I know that as long as I am running my press with the density variation as close to zero as possible**, then my work will pass an ISO match which is good enough for me and good enough for the client - it matches the proof which was passed OK, I don't even need to continually check it, it just passes.

What more can I ask from a system?



**This assumes that my dot gains and general press conditions are good.

 

[meddington]

By having these standard colour targets for inks etc., which are not obtainable in practice, the approach accepts that one will have errors right at the start. The idea that systemic errors are acceptable is very strange to me.

I think they are made acceptable for the fact that the are often unavoidable, considering that obtaining a substrate with CIElab values in conformance with ISO12647-2 is exceedingly rare. Moreover, substrate is often chosen for characteristics other than whiteness, and printers are forced to do they best they can, and compromise on other aspects.

Your points are certainly well taken though.

 

[Disappointed]

Yes, the substrate is very rarely the right colour, I know of only one make of paper that is.

If it's super-critical then a wet-proof is needed as proof matching will not be accurate if the paper is off-colour.

However, we can recalibrate our proofing system to match a certain substrate, luckily this level of matching is rarely needed for us.