7 May 2012
Black and White with Ultrachrome K3 Inks: Fade Tests for Three Workflows
I have used Ultrachrome K3 inks for my black and white printing since 2009. Initially, when I first had a K3 printer, I carried on with the Quadtone Rip workflow, because I was used to it from the previous generation of Ultrachrome inks (which required it for neutral monochrome prints) and it worked for me. Since then, I've used Epson's Advanced Black and White mode (found in the printer driver) and have trialed using the colour driver with colour profiles made with Datacolor's Spyder3 Print Extended Grays profiling targets.
One reason to stick with the QTR workflow is that it uses the least coloured ink of the three workflows to produce black and white prints; Epson's Advanced Black and White mode uses slightly more colour than QTR and the colour driver uses slightly more coloured ink again.
The advantage of using the Epson colour driver is that it is fully colour-managed. In QTR or Advanced Black and White, only luminance can be colour-managed (via an icc profile produced by the QTR-Create-ICC application). The more fiddly part is that getting a neutral hue on different papers requires careful examination of test prints, then making adjustments and more test prints (and getting a bit neurotic in the process). With the Epson colour driver and Datacolor's Spyder3 Print Extended Grays profiling targets, however, the job of getting a dead neutral print is done for us, as the workflow is completely profile-managed. One can also add profile-managed spit-tones if one wishes. Split toning is also available in Quadtone Rip and I've found that in some papers it makes a huge difference.
I have made a comparison fade test to see how stability compares between the three workflows.
21-Step graded test strips were printed (using photo black ink) on the same sheet of resin-coated paper*, as follows:
1. Epson Colour Driver, profiled with Datacolor's Spyder3 Print Extended Grays targets.
2. Epson Driver, via the Advanced Black and White mode.
3. Quadtone Rip.
* I used resin coated paper rather than exhibition quality paper, because the only variable that mattered was the workflow for laying down ink; so the paper choice was irrelevant, as long as it was the same paper for all tests.
I printed two copies. One was stored in a drawer and the other was taped to the inside of in a sunlit north-facing New Zealand window. The location is not perfect, because of trees, which block the direct sun for roughly half the day (more in winter); but it's in the hottest part of the day that the print gets direct sun.
New Zealand has higher levels of UV than many other locations. An explanation and video are featured on the NZ Science Learning Website. To summarise:
1. The closest the sun gets to the earth is during December/January (the Southern Hemisphere summer), because the earth travels in an ellipse. This adds 7% to the UV levels found in summer in the Northern Hemisphere, at the same latitudes.
2. There is less ozone in the Southern Hemisphere which adds another 10% to our UV radiation.
3. We have relatively clean air, which adds another 20% to our UV radiation.
I have scanned the sunlit print at three months, to compare any colour shifts (caused by the coloured inks fading at different rates).
The most obvious first observation (which has nothing to do with the purpose of this test) is how critical it is that we print with pigment inks: the date label at the top was printed with a (so called) Photo Signature Pen and it has completely faded from sight after six months. The bottom label was printed with a pigment felt-tip pen and it's hard to detect fading.
The six month period of exposure has now elapsed, so here are the results. The scans are a rough and ready indication of the effect of six months of UV exposure More precise measurements are found in the Lab values below the scans. [View Lab values .txt file]
My conclusion is that the difference in hue shifts between the different work flows is negligable. As a result, I have been using whichever workflow best suits the paper on which I am printing. On Entrada Natural I got the best results using QTR. On Ilford Gold Fibre Silk, I've fround that the Datacolor Extended Grays gives the result I was seeking.