My guys run almost all dark jobs at 1440 x 1440 (white layer) and 720 x 720 (cmyk layer) - for my printer, it doesn't make sense to print the CMYK over white ink at higher than 720 x 720, because it over saturates the ink and causes bleeding issues. More importantly, it ruins the color accuracy between the screen and the shirt. However, on SPOT COLOR jobs (a few solid, bright colors that really need to pop), printing the color layers at 1440 x 720 (over the white) can really add something - we offer this as a "color boost" option, for our customers. In the beginning, we used to assume that everyone wanted "bright" prints - since many people are more concerned with accurate prints, we now allow the client to determine if their individual artwork would benefit from "over saturating" the color, for a small additional cost.
For light garments, we go back and forth between 1440 x 720, and 720 x 720. Again, the higher res lays down more ink, and makes for a deeper print, but it sacrifices more color accuracy than I am willing to give up, when printing photographic images; it also tends to bleed too much ink into the image, causing deterioration in the finer details. Therefore, we print many jobs at the higher resolution, but we print most photographic jobs at 720 x 720.
A few things to consider, when comparing your results to mine:
- We are printing in single-CMYK mode, not dual CMYK, since we also have white ink in our printer; this means less ink is being laid down in a single pass, compared to a dual-CMYK setup (no white ink). In my opinion, the amount of ink we are laying down is MORE than enough! In fact, as a matter of argument, let's assume that I had 8 channels to print the white ink, and 8 channels to print the CMYK ink - at that point, based on my current results, I could probably then print the white ink layer at 720 x 1440 (or 720 x 720) and the CMYK layer at 720 x 720 for "color boost", or 360 x 360 for accurate color.....
- When printing white ink, the 1440 x 1440 mode lays down more ink than we need, sometimes. This occurs when the white ink is nicely mixed in the lines (ie, we haven't stopped printing for awhile), the humidity and temp are in the right range, and everything is firing away nicely. However, since this is not ALWAYS the case (although, in reality, we have very few actual problems with our ink flow), I have not taken the time and effort to dial down the percentage of white ink, at that resolution. Certainly, I could save money if I did this, and probably still get a 100% perfect white under base (without pooling)...... However, since the white ink does not ALWAYS come out at 100% opacity (ie, it settles a bit, in the lines, or humidity is too low, etc), printing at 1440 x 1440, 100% ink deposit, ensures that the white under base always looks great, even when the white ink is not at 100%. Again, we actually have VERY FEW ISSUES with our ink clogging, ever - however, I do notice that the white is not ALWAYS as white as it could be; some of this might have something to do with the pretreatment process, as well, although it is not as exacting as it used to be.
- We print almost EVERYTHING in uni-directional mode, at the moment. Why? Well, I ask myself the same question, every damn day - why is it that every other printer on the planet seems to be able to print in bidirectional mode (INCLUDING THIS DIY UNIT, WHICH IS AWESOME!!!!!!), except for my machine??? Personally, I feel it is because the people who brought it to me didn't know how to properly tune it up, so that responsibility has fallen on my shoulders; eventually, I will have this thing printing in bi-directional mode - in the meantime, the incredible detail and repeatability that we are getting certainly takes the edge off the pain of slow production rates.... We have made some good progress in the past week or so, dialing in some various Epson settings to enable successful bidirectional printing, and we might actually be close..... Time will tell.
Well, hope that information helps!