Strange dot

[meddington]

Just an update on this. We tried using a 200lpi round dot with this customer. The irregular dot structure dissapeared but the print was extremely flat. Even with dot compensation curves etc. We can not continue using the 200li round/square dot as it definately creates print problems. It appears as if it is mottling on the press. I have now had it at more than one customer who uses the same dot structure and line screen. We have now taken them down to 190lpi which seems to be a standard screen set for this supplier and now the dot is not irregular anymore. We are though having a situation where the print looks a bit flat. It seems to have somehting to do with the midtone areas. Any more suggestions?

This might have less to do with the dot shape/lpi and more to do with tonality. What are you targeting for tonal response and how are you attempting to achieve this?

 

[LauraMinter]

We are printing to ISO 12647-2 standards. Created a linear set of plates, run the press to ISO Ink standards, get the dot gain values and then create dot gain compensation curves. Our dot gains when we go back to press is spot on, as well as the ink densities but it just seems to be lacking something. Not sure what.

 

[gordo]

Just an update on this. We tried using a 200lpi round dot with this customer. The irregular dot structure dissapeared but the print was extremely flat. Even with dot compensation curves etc. [SNIP] It seems to have somehting to do with the midtone areas. Any more suggestions?

Good that it got rid of your hairy dot issue. However, all things being equal, there is nothing about a round dot that would result in presswork looking "flatter" than another dot shape. There is likely something else that's causing the problem of "flat" looking presswork - unfortunately the list of possibilities is virtually endless. I would start with an ISO certified proof that contains subjective and objective reference images - does it look flat? Does your presswork align with the proof if you simply print to the numbers ignoring the proof. If not, then, ignoring the screening you are using, you need to determine what aspect of the presswork would cause a failure to align with the ISO certified proof. Start with the SIDs, RGB overprints, and L*a*b* values. Then look at the dots for ink/water balance issues, slur, doubling, voids, squeeze, etc., etc., etc.

best, gordon p

my print blog here: Quality In Print current topic: Custom Halftone Dots

 

[Lukas Engqvist]

If you look at the ISO standard there is a higher TVI as lpi increases, you will either need a repurposing, or you will need to acheive the same TVI as the standard profile irrespective of dotgain curve. To have a standard where the tonality of a 50% tone varies depending on raster because that is what happens with linear plates is just plan silly IMO. Clients are more concerned about getting consistent colour than what raster we intend to use.

 

[Tommy B]

Strange Dot

Strange Dot

If I was getting that dot and were using a HQ Rip, I would proably delete the screen information in the rip and let if rebuild. Sometimes tha screen software gets corrupted. You may want to ask you RIP vendor if that can be done on your RIP

 

[gordo]

If I was getting that dot and were using a HQ Rip, I would proably delete the screen information in the rip and let if rebuild. Sometimes tha screen software gets corrupted. You may want to ask you RIP vendor if that can be done on your RIP

Tommy B is correct. If that doesn't work contact your workflow vendor and see if they can reset your screening parameters. Here's some microphotos of two other hairy dot situations where the screening parameters were incorrect.

best, gordon p