August 14, 2008

RIP work, pushing photographic quality with ink

Filed under Technical Articles | by Tyler Boley @ 3:26 pm

There are many reasons for a print studio to use a RIP, and I won’t go into all of them here. Most probably think it simply provides the ability to make larger prints, and manage print jobs more handily. More refined and consistent color control is another primary reason. Each ink color is iteratively linearized, limited if necessary, and total ink going down on each paper is carefully optimized as well. Every batch of paper that comes in is relinearized. These controls also make it possible to print on more unusual materials like Japanese papers, requiring careful limiting. Additionally, having the each color so well behaved makes the work a profile does much less problematic, it has far fewer problems to solve, so can remap color to the output space more accurately.

The RIP here, Ergosoft StudioPrint, takes control of how the ink goes down to a new level of detail, some might say obsessive. However, testing these controls in depth has resulted in higher image quality from the Epson printers than the OEM driver can deliver. Of course, finer and finer photographic image quality is the goal. Fellow ink enthusiast John Moody and I were exchanging a lot of information about RIPs and driver tests, and he kept describing a problem with dark color to black gradations he was experiencing with his Epsons, including his new 3800 which was supposed to have an improved dither, and had me print a red to black grad to look at. Then he sent me a scan of his output of same, complaining that his Epsons had a rough quality in dark saturated tones due to excessive black dots. Repeating his test with the 9800 here with both the Epson driver and the RIP reinforced his findings.

red to black output comparison

red to black output comparison

This is a portion of an image simply created in Photoshop with the grad tool, from R-G-B 255-0-0, to 0-0-0. Both were printed on PhotoRag and drum scanned at 4000ppi, downresed bicubic sharper to these display jpegs. The Epson driver was set to superfine 1440, microweave super X checked, high speed off, finest detail on, edge smoothing off, no color management, through a custom EyeOne Match RGB profile, Relative Colorimetric, BPC on.

The StudioPrint RIP settings were 1440×720, with custom dither, pass, dot size, etc., settings. More on this later. The image was first converted to the custom Ergosoft GPS Profiler CMYK profile in Photoshop, Relative Colorimetric, BPC on.

It seems clear that the Epson driver jumps to some large dots sizes and/or darkest black quite rapidly on it’s way to black. There are 3 blacks, with 3 dots sizes available to each, in the Epsons at this print resolution. The particulars of how all that is utilized is user configurable in the RIP, but not the Epson driver. So the gradation from red to black (in this case) is much less dotty, as light light black, light black, and finally black are brought it, with appropriately small dot sizes as configured, until large dot blackest black ink is necessary for the required density.

The red to black grad shows this quite clearly, and had I chosen to downsize the scans less, it would be even more obvious, but some might say nearly irrelevant at microscopic viewing. Another file with more colors gradating in and out of each other shows the differences as well.

Color Gradation Comparison

Color Gradation Comparison

In this comparison, the light delicate colors also show that the use of dots sizes and light inks can be optimized beyond the OEM driver performance as well.

It follows that light inks, and dot sizes, could be optimized, then more dot positions could be utilized to translate image information to paper, instead of being used up in color dot clusters required to build a image color from CMYK inks. Therefore it seems that more photographic detail from the file and subtle color gradations could be realized on paper. This does turn out to be the case-

Photographic Color Detail Comparison

Photographic Color Detail Comparison

How much does this matter? How visible is this in a print to the naked eye? It depends on your eyesight, and more importantly your expectations. This is not the point here, the point is that it can be better. This is something people coming to a shop like this can expect, image quality relentlessly pushed to “better” than one can easily do themselves at home with off the shelf products. I should point out that tinkering with these settings and constant testing has been ongoing since these controls were made available to us in January of 2006.

In addition to several dither and pass options, the amount of each of 3 dots sizes in each of 8 inks is user controllable. The overall amount of each light light, and light inks is overall controllable, and each “color” overall controllable. For example cyan has a cyan, and a light cyan component. Each of those two has 3 dot sizes, the percentage of each of those 3 user selectable. In the case of black, there is a light light black, a light black, and a black ink, each again with 3 selectable controllable dot sizes, each component overall limitable, and the combined color (black) overall controllable- not to mention linearized iteravely to 80 density points. Is all this control necessary? Well I can say for a certainty that it can drive a normal human nuts playing with this stuff, and there are a myriad of settings that are terrible. But experimentation has proven that there are approaches to minute control of how ink goes down that moves photographic performance with ink forward, and that’s of great interest here. Should you want to know about this stuff? I really don’t think so, for your health, but don’t you think I should?

There is no real proven approach to this control, perfecting resolution and lack of bleed with each color can result in total ink problems in profiling, so there is a lot of back and forth with this stuff. If you want to know what my settings are… well, I’m afraid not… they are evolving, I still think they can always get better, and this work has been ongoing for well over two years. Those who get to benefit from this work are the artists who chose to come here and let me print for them, who expect the highest possible print quality. It’s all small steps, perhaps no one thing makes the difference, it’s the growing combination of constant small steps that do.

We’ve moved from traditional proven processes and materials that have yielded the finest quality photographic prints, to processes and materials few know that much about, in only ten years or so. It is imperative that this be a step forward, not backwards.

This kind of work has greater impact with black and white printing, and the next write-up will be an in depth look at the work done here with multiple black inks, and how these various approaches compare with traditional silver materials.

Tyler Boley

August 2008

I decided after posting all of this it may be of slight interest to complete the overall by adding the following-

© Tyler Boley

© Tyler Boley

A 5×7 Ektachrome, made with a questionable 90mm lens.

drum scan from film

drum scan from film

A portion of the file used on the above tests, a transparency drum scan.

Ciba

Ciba

and for grins, the same portion of the image scanned from a very old Cibachrome print I dug up, approximately 1.6 enlargement. Interestingly, because of the continuous tone, absence of mechanical artifacts and dots, I would say it is more photographic than the ink. It is clearly less sharp than the blazing drum scan, perhaps because of enlarger lens quality or imprecise focus, or I suspect, the drum scanner does not have the same limitations of and optical enlargement process from a single stationary lens. I definitely prefer the ink print on fine paper, it’s a completely different animal from the Cibachrome, and intended to be so. Nonetheless, those qualities unique to photographic craft still have much room to improve.

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