In his essay on The Modern Digital Negative, Dan Burkholder very sensibly advises us to make a test strip to determine the maximum exposure required to turn our photographic paper the deepest black or color possible. I tried doing this on a shett of Arches, hot press, 140 lb watercolor paper sensitized with a Cyanotype emulsion. Exposing some of the paper through the Freestyle OHP film I am using to create digital negatives, I moved my opaque piece of black foam core every 30 seconds, for a total exposure time of 6 minutes and 30 seconds, in the full sun. The 30 second exposure can be see near the top, where the Cyanotype blue is the lightest. The previous 30 second exposure intervals are a bit harder to detect. I figure that after about 6 minutes and 30 seconds of exposure through the OHP film, the blue exposed through the film was just about as dark as the blue that did not have the film covering it.
What I did was, as Burkholder says is , “…finding your standard printing time. This is the exposure time needed (in seconds or minutes depending on the type of printing) to create the deepest density in your print.”
Having determined that my standard printing time is 6.5 minutes under full Florida sun on a June day, I needed to move to the next step and decide which color combination on my Epson 2400 blocks the most light. Or, as Burkholder says, “…once you know your standard printing time, your next step in finding what color negative will create the most suitable densities for your printing process is pretty easy. By printing a chart with lots of colors (using your standard printing time) you can quickly determine the color negative that will create the best density for your printing.”
So, I printed out a copy of his spectrum file on my OHP film:
Then I exposed a piece of Arches paper, sensitized with the Cyanotype solution, under the digital negative of the spectrum file for 6.5 minutes:
What that proved to me exactly what Ron Reeder says in his article Dig Negs with 3800, namely that “…Yellow is the highest UV absorber in the K3 inkset after matte black….” He is talking about the Epson 3800 printer. While I have the Epson 2400 and not the 3800, I believe the inks are the same and thus the outcome is the same.
Regardless of what kind of printer you have and what kind of ink it uses, you can do the same test and figure out the optimum color setting for your digital negs.
Although everybody advises it, I seldom do it. However, this time, when making a digital negative, I included a step table. Here is a scan of the print. I think it came out pretty well, but am not sure if, looking at the step table, I need to monkey around with the curve or not.
[I am pulling my Cyanotype info together on my website – it is still a work in progress – your comments/feed-back/ideas are greatly welcome]