I think I have everything working! Walker, thanks again - the trailer sheet is vital to avoiding star wheel tracks but with a number of other steps with the 4900, which I describe below.
The star wheel bars (two of them) drop down near the exit point of the print, when a sensor located in the front-right area, just before (towards the print head) the bars, senses paper that is curling upwards. I tested this out while a sheet was printing, by sliding in a long scrap of paper about 5 mm above the output bed in the vicinity of the sensor, and sure enough, the star wheel bars dropped down and remained down for the rest of the print run.
Removing the star wheels is easy, if you are prepared to
a) remove the upper front cover (quite easy)
b) quite physically flip the star wheel tracks into the active, down position,
c) and then with a very thin and long pair of needle nose pliers gently coax each pair of wheels out. They come off quite early, and are held in place by a single spring-spindle.
I did this to just one pair of wheels, and then, just to be sure, managed to put it back into position. It takes some patience and dexterity with two pliers, but can be done.
Having tried this, I wondered if there was an easier and less drastic solution.
So, back to Walker’s plan, and with the following extra steps, presto! no track marks, and a much easier solution:
In the Epson Printer Utility (v4), access Epson LFP remote Panel 2
Select the printer (4900 in my case) and then Custom Paper Setup
Set Reference Media Type to Premium Glossy Photo Paper(170); Paper Thickness to 1 (x.1mm); Platen Gap to Narrow and most importantly, Drying Time/Print Head Pass to somewhere between 10 and 30 (0.1 secs). I tried various settings and 20 (2 seconds) seems to work well.
Give this group of settings a custom name, Save… and Activate it. You should see the preset number appear on the printer’s console.
- For each sheet of Pictorico UP OHP, I am taping, as per Walker’s guidelines, a trailer sheet about 150% longer than the transparency sheet to the P UP OHP. Be sure to have exactly the same width for all pieces and tape edge to edge securely and cleanly.
That’s it. The pauses between each head pass seems to give the film just enough time to loose its upward curl by the time it gets to the sensor, and the star wheel bar does not drop down. I have done this with about 10 sheets of film with no stellar descent.
So, Occam’s razor - either that, or I have been a bit of a dolt. Sorry to have taken up Walker’s (and other’s who may have considered responding) time!
I am thrilled with the output from the default Piezo DN PtPd_default curves. I hope to print some of these negs in the next few days, and then, if necessary, get into fine-tuning the curves. Thanks!