Andy Piper , Feb 03, 2003; 05:03 p.m.
I just made the following discovery - which has substantial
implications for printing quality, so I thought I'd pass it along.
Using an Epson 1280 printer - black-ink-only mode - 9-10 mil paper
weights: Setting the print head height to the "+" setting produces a
very significant decrease in the apparent size of the printed dots and
a corresponding improvement in tonal reproduction.
Here's how big the difference is - a print made at 360dpi and at the
higher print head height setting produces finer dots and smoother
tonality than using 1440 dpi at the "0" print head height setting.
The effect is consistent and repeatable, and occurs predictably across
a wide range of paper surfaces in roughly the same paper weight class:
Epson Heavyweight Matte, Epson Premium Glossy, Epson ColorLife (and the
equivalent Ilford Classic Glossy and Pearl papers) and Tetenal Portrait
Pearl Lustre papers.
I'm no expert in fluid dynamics, but it appears that as the ink crosses
the wider gap (roughly 1 mm) when the print head is higher, it
disperses into a jet of fine droplets instead of a single drop.
This is somewhat consistent with another 'print head height' effect I
noticed printing color on Colorlife-type polymer papers: a very faint
dusting or "5-o'clock shadow" of ink in the white border on the side of
the print nearest the right side of the printer (where the controls
are) when the print head was at the (+) setting.
At first I though this was mechanical 'rub-off' of ink due to the
swelling of the ColorLife polymer surface, but it actually disappeared
when the print head was lowered (which should have INCREASED any
mechanical rubbing). Which makes me think the ink cloud formed by the
wider gap at the "+" setting was really being "blown" off the edge of
the print area in a fine cloud by the 'wind' of the print head passing
on the back stroke. (Again, I'm no expert on venturi effects or fine-
particle dynamics).
At any rate - two significant effects based on where the printer head
is set, which may be of interest if you're using ColorLife papers or
experienting with black-only printing - at least with a dye-ink
printer. Someone might experiment with a pigment printer to see if
anything similar occurs.
It also implies that if you use papers significantly heavier than the
standard 9-10 mil Epson/Ilford papers, you may get a visible increase
in dot size and decrease in tonality even at the printer's "+" setting,
since the thicker paper will reduce the jet-to-paper distance.
And it implies that if you've tried black-ink-only printing of B&W
pictures and thought the dots and tones were much too gross - you might
check your print head height setting. At the "0" setting they are
indeed gross, but at the "+" setting they improve by an order of
magnitude.
Ron B , Feb 04, 2003; 12:33 a.m.
Andy, how does one change the printer head setting on a 1280? Is it possible to do so on an Epson 1200?
Andy Piper , Feb 04, 2003; 12:45 a.m.
On the 1280: Right-hand side, underneath the flip-up main printer cover (the one you raise to change the ink), on the top above the various control buttons, is a lever that moves forward and backward in a slot - the back setting is marked "+" and raises the whole print-head/ink carriage away from the paper, the front setting is marked "0", which lowers the print head closer to the paper.
I don't know for sure about all other Epson models, but on my old Epson 600 it's in the same place, so I assume it stayed there for all the models in between.
Angel O. , Feb 04, 2003; 07:10 a.m.
From the fluid-mechanics point of view it doesn't make sense. It's a nozzle, so the further away it is from the paper, the bigger the dot.
Maybe the "pump" is not powerful enough to provide enough fluid (=ink), so that the available volume is torn (over the increased distance) away into a spray covering the supposed "bigger-dot area". This would explain your observation: "...fine droplets instead of a single drop". So it makes sense again... ;-)
There you go, a pump should never be under-motorized...
peter nelson , Feb 04, 2003; 08:32 a.m.
. . . Doesn't Work
As tbe Car Talk guys say . . . . "B-OH . . . GUS!"
I tried it with my 870 (see my comments elsewhere in the forum for why it makes no sense, so I don't know why I let Andy talk me into this . . . ) and there was no improvement.
Using Epson Heavyweight Matte paper, 1440 DPI, High Speed turned OFF, black only, I did one with the height adjustment on "0" and one with the adjustment on "+". I then scanned the results on a flatbed. The images, respectively, are at:
http://studio-nelson.com/tmpimage/bo0.jpg
and http://studio-nelson.com/tmpimage/boplus.jpg
The image is part of a test image I use - the numbers represent the RGB (R=G=B for grayscale) values of the patches.
As I said below, this is just another GIMMICK to try to get around the fact that black and white printing with inkjet technology isn't quite there yet.
Personally the best results I've had are to print with my 2200 black-only on artist's media like Canson cold-pressed watercolor paper, or Canson toothed paper where the ink spreads out and blurs together anyway, or to print grayscale with the full inkset and default driver settings on toned media (e.g., sepia-toned gesso-on-canvas) to swamp the 2200's metamerism problems. But at least I admit that those are gimmicks until decent B+W inkjet printing comes along.
peter nelson , Feb 04, 2003; 08:38 a.m.
On a quasi-related note, in another thread, when I complained about the 2200's metamerism problem Daniel Staver said You need a RIP to get rid of metamerism. iProof PowerRIP 2000 and ImagePrint 5.0 will both give you prints free of any metamerism. Rumors have it that the new Epson StylusRIP will do that too, but it's not available yet.
They achieve this by not using the yellow ink to mix neutrals. The yellow ink is supposed to be the main cause of metamerism on the 2200.
Anyone care to explain this? In color theory Cyan + Magenta = Blue. So if you take away the yellow ink why wouldn't that produce blue-toned prints?
peter nelson , Feb 04, 2003; 08:48 a.m.
BTW, the scale on the two sample images I posted is about 2.5 cm horizontally.
Daniel Staver , Feb 04, 2003; 11:11 a.m.
I just tested this on my 2100. I do get a slightly finer pattern if I set my printer to thick paper mode. The difference was visible at a normal viewing distance from the page.
As I mentioned in another tread it's possible to mix a neutral gray without yellow because the light black on the 2100 is very warm brown, not neutral. The matte black is also warm, but not nearly as much as the light black. My guess is that this wouldn't be possible if the light black was completely neutral. Of course, then we wouldn't have to use all colors to get neutral grays anyway...
peter nelson , Feb 04, 2003; 11:40 a.m.
I just tested this on my 2100. I do get a slightly finer pattern if I set my printer to thick paper mode. The difference was visible at a normal viewing distance from the page.
By "thick paper" mode do you mean the manual feed setting? Also what exactly do you mean by a finer pattern? Do you mean the dots for a given grayscale value are closer together, or the dots are smaller, or what? As you can see from my sample output of the 870, the dots were neither smaller nor distributed differently. Could you post a sample scan like I did?
As I mentioned in another tread it's possible to mix a neutral gray without yellow because the light black on the 2100 is very warm brown, not neutral. The matte black is also warm, but not nearly as much as the light black. My guess is that this wouldn't be possible if the light black was completely neutral. Of course, then we wouldn't have to use all colors to get neutral grays anyway...
I called ColorByte to ask where I could see sample output of ImagePrint RIP before plunking down a pile of money on their product but they said they don't "do" that as a matter of company policy, nor do they have a dealer network where such prints can be seen unless you live in LA or Chicago.
I would be very suspicious of any company that has a policy of selling a such a pig-in-the-poke. The fact that there are individuals who claim that it fixes the metamerism problem is not very convincing because there were perfectly respectable people here who claimed the 2200 didn't have such a problem in the first place! People's eyesight, viewing distances, ambient light, choice of subjects (a gray cat in the fog versus Aunt Martha on Aruba on a sunny day), and tolerance for color shifts, vary so much from individual to individual that personal testimonials mean nothing.
Andy Piper , Feb 05, 2003; 06:23 a.m.
Peter: Thanks for posting examples. I can't post any yet myself since I don't have a flatbed scanner or SLR mit macro lens (I shoot rangefinders) to make a high-res image of my printer dots - but I'm working on it.
I agree with you that inkjet photo printing (with any number of inks) still has its weak points - but I'm not sure 'gimmick' is the right word for creative workarounds.
One might just as well complain that: "Graded photo paper is just another GIMMICK to try to get around the fact that film can't automatically adjust develop for each frame to the proper contrast range. Even after 165 years silver-based photography really isn't quite there yet."
I can't think of anything more non-intuitive (or perhaps 'gimmicky') than using 4 or 6 or 7 COLOR or gray-shaded inks to try and produce a simple black-and-white image - but is it really that much more strange than making B&W prints with COLOR filters in the enlarger (i.e. on multi-grade paper)?
You do what you need to do to bend the materials to your will.
