QTR-Quadtone RIP

Been using PrintTool (PT) since the day it came out, and AFAIK w/o any problems. But I generally print on larger paper, so perhaps I overlooked this, but...

I had a client ask for prints on (sheet fed) 11 x 14 paper. I have my own sizes, all with 0.0 margins. I printed the image after centering it (and verifying that PT's top and bottom margin were identical)... only to discover that the top margin (the edge that comes out of the printer (a 9890, run from a Mac with 10.11.4) first) was off by about 2/10s of an inch, making it smaller than the bottom edge by 4/10s.

Changing the paper margins themselves made no difference, and I'm now in the position of having to increase PT's top margin by 0.20 on every print to get measurably identical top/bottom margins on the final print.

I do not see a way to adjust the physical feed of the printer's starting position, and I'm really curious as to what has gone wrong.

(No: it's not just 11 x 14 paper: it happens with every size I've tested.)

Anyone with suggestions or comments? TIA.

... and indeed, it did make a difference. It's still not a match on the top and bottom, but the difference has gone down to 1 1/4 vs 1 5/16 - a 16th of an inch instead of a far more visible 3/16.

Interestingly, changing the top margin on my own paper to match the 1/8 inch of Epson's top margin did not affect the outcome, so apparently it's some combination of the top and bottom margin (.556) at play.

Given all that, and the fact that it -still- was off by 1/16, I've decided that it's actually easier to keep all my custom paper sizes (with 0 borders all the way around) and just adjust the top margin in PrintTool.

I get an exact match, top and bottom, by adding 0.19 to the current top setting. That's really pretty easy, for the math adverse, since it's just adding 0.2, and subtracting 0.01.

So: if the top margin shown on center is, say 1.29, then adding 0.2 = 1.49, and taking out 0.01 yields 1.48.

That is, by the way, approximately 3/16 of an inch.

At least for me, running El Capitan, PrintTool, Epson's driver and sheet feeding with 0,0,0,0 margins, this technique produces exactly balanced top/bottom margins.

Finally, as to "why so fussy?" (in case any lurkers are wondering) it's this: my client specified 11x14 paper, and some of her images extended to within 1/2" of the edge when properly centered. When the centering was thrown off, it resulted in a print that could not be properly matted.

I've been using Epson printers since the 2000 and have never heard an explanation of what Epson is doing internally with its math regard print placement and size. Their manuals contain tables showing what appear to be arbitrary "adjustments" to paper size and image adjustment to print borderless, but no explanation. In fact, a few years back, I called Epson pro tech support and directly asked them. They had no explanation either: "Just do what it says on the chart. I don't know why.";

As a retired programmer, I could (and have) guessed at a few explanations (their ALU; the dictates of stepper motors and so on.) But the mystery remains...

Thanks for your (usual) patience and courtesy, Roy.