CHROMiX

HP 5500 Print Quality Question

I’m having some quality issues with my HP DesignJet 5500UV.

I am getting small dots in some solid colors. They kind of look like pepper. I also have this problem with the other three channels (CMY) but it’s most abundant in the black.

I also have a very granular (grainy) black that kills all the details in anything phographed black (i.e. can’t see the creases in a pair of black pants, justs mush).

I have a pc with wasatch softrip, gretag macbeth profile maker publish pro 5.0, and an eye one spectrophotomer.

I turned off the varware in Wasatch, set the settings to LcLm, 10 pass, unidirectional. I went through and limited my total ink and limited the individual channels using precision stochastic screens for half toning. I scanned in a linearization curve and made my own output profile using both 1.1 CMYK Chart and ECI2002 CMYK Chart (for 2 different profiles).

The front panel settings on the HP are set to productivity semi gloss at max quality. I am using a luster paper made by intelicoat.

I’ve heard that it could be a ucr/gcr problem, that the grainy black is due to a lack of magenta and yellow, and also that it is a problem with the profile.

If it is any of these issues can someone please go into detail as to what I should try especially if its due to the profile.

Also how can I tell if my gray balance is good or bad? And if it is bad how can I fix it? Should I have good gray balance before I linearize or is it something that output profile fixes?

I would appreciate any help.

Bobby

In my experience, the pepper look in solid colours is simply the black. This is simply a part of stochastic screening and CMYK mixing. If you want to avoid this, you’ll have to adjust your UCR/GCR. What is happening is your black is being added too soon. That is, black is being added to light colours, where the black is very noticable. What you want is your black to come in later, into darker colours, where the black is less noticeable. If you have UCR/GCR control, you can adjust the point at which your black starts. Just remember, adjusting UCR/GCR can seriously affect your colours. I find it’s better to live with the peppering and get the best colours I can get (from 2 feet away, the peppering vanishes and this is a poster printer after all).

As for your granular black, that seems unrelated. I can’t tell what’s going on there.

My rule of thumb is give the profile the least amount of work to do. The less it has to worry about, the better it will do at it’s job. Before profiling, gray balance as much as you can without completely limiting your colours and shrinking your gamut. Then let the profile tweak the rest. So, yes, do some rudimentry gray balancing by restricting your inks before linerization. You can test your gray balance by printing Lab gray swatches and reading them with a spectrophotometer. A perfectly neutral gray will have a* and b* values of 0.

Anyone may correct me if I’m wrong.