Colour managing a Di Press...

[Disappointed]

Dave you are correct, the curves should have no effect on solids (but check with a high power magnifier to ensure there is no dot drop-out)
Which Toyo set are you using? What sequence are the inks running in? Is there any dirtying of the inks in the duct that could skew the hue of the cyan and magenta?

The solids look good through a loupe, we are running Toyo MZ Aqualess Eco in K-C-M-Y order as that is standard for this press.

We sometimes get a bit of yellow contamination but is very job dependant.

Dave

 

[LSW]

Maybe try taking single colour pulls and measure them with the spectro to ensure you aren't getting any back trap contamination from the unit before?

 

[Disappointed]

Hmm, done that, solids are clean.

 

[LSW]

How did they measure up? Still outside of 5 deltaE on cyan and magenta?

 

[Disappointed]

Pretty much the same, slight variations due to density but still wrong regardless.

 

[LSW]

Not a good start to be hampered by your ink set. If your trapping colours are close to standard I think it would be worth calibrating curves to ISO and evaluating the results against a Fogra standard proof before looking at .icc profiling.

 

[Disappointed]

Yes we have done that. We used Bodoni Press-Sign for curve creation. It works but not quite, the colours are a bit flat and lifeless, we have to punch the yellow and black to give the pictures more bounce and a closer match to the proof.

We can get close but not close enough.

I must add that we are not new to this, we have had the press over a year now and have never really been happy with the colour as standard, with tweaks to tone curves in the rip, we can get close so we are sure it can be done but we can only really tweak the odd density say 70% by eye, it needs the whole 0-100% range analysing for best result. This i presumed is similar to what profiling will do but in a different way.

Dave

 

[LSW]

Dave,

I would really like to come over and try to help you out, if only to gain some experience of the Presstek DI and your problems. There would be no charge. Let me know if you're interested. I can come to you any day next week.

 

[LSW]

Hi Dave,
Did you ever get this nailed down?

 

[rich apollo]

Dave,
I was just perusing this thread - and a had a thought. It looks like you are (or were) having trouble nailing down what SIDs to run your ink set at.

Have you tried running a form like the attached? You want the density to vary - really you want the density to progress - across the sheet. If you run even ink keys across the sheet, the mechanical take-off of the ink should give you a density progression across the sheet for each color. This way you can check a bunch of densities all at once, and you can create a high-low graph to see what kind of tolerances you have with this ink set.

Something else to think about, it's been my experience that the overprint colors are more important than the primary solids. Get C+M, C+Y, & M+Y to conform within the 5 deltaE window.

Anyway, just thinking out loud.