The chapter called “Desktop negatives” of Sarah Van Keuren’s book “A Non-Silver Manual: Cyanotype, Vandyke Brown, Palladium & Gum Bichromate with instructions for making light-resists including pinhole photography”, written by Sandra C. Davis
A series of experiments I made after taking a workshop with Dan Burkholder, author of Making Digital Negatives for Contact Printing*
I begin by scanning my 35mm or 120 black and white negatives into the computer using a Nikon Super Coolscan 8000 scanner. This scans film only by pulling the film into the scanner and pushing it back out when it is done. I then manipulate the images in Adobe Photoshop on a Macintosh G5 computer. Most of the manipulation consists of various ways of burning and dodging areas of the image, as I would normally do in the darkroom, if I were printing regular ‘silver’ black-and-white prints.
The final output is on a transparency film made by Pictorico, (available at www.Pictorico.com), which has a thin clay coating on the surface that holds the ink-pigment. The negatives are printed in ‘color’ from an image that appears black and white in Photoshop, using an Epson stylus Photo 2200 printer. This printer was designed to print using a pigment base ‘ink’ rather than the standard dye base ink. Epson claims their pigment color is “fade proof” for 200 years. I use it, because the pigment dries quickly with no streaking or puddling.
The process of making ‘desktop negatives’ is different from making negatives in Photoshop and sending them to an imagesetter. There is a series of contrast curves that must be applied to make the printer actually print the image as it appears on screen. When the image looks great on screen the last three steps before sending it to print are: 1) Turn the image into an RGB file. 2) Put a contrast curve on it as an adjustment layer, which makes it appear ‘wrong’, (it makes most of the image appear ‘blown out’). 3) Turn it into a negative by putting an ‘invert adjustment layer’ on as the top layer. These contrast curves are the genius of Dan Burkholder who designed most of the curves for printing platinum from desktop negatives. The goal is to place a step tablet on each image and make this print with accurate percentages of 5% on up through 100% in the non-silver process, i.e. cyanotype, palladium, or vandyke. After the print is made from the negative in one of the non-silver processes, it is evaluated for accuracy of the step tablet. Once this is achieved, all images with this contrast curve added should print accurately. Note that each process has a different contrast, so one curve has to be ‘designed’ for palladium and a different curve must be ‘designed’ for cyanotype. I have found that the same curve can be used to print a negative that can work for palladium as well as gum bichromate. In Photoshop, curves can be applied on separate layers and saved as ‘curve presets’ to be reused on future images.
The other issue of printing from computers is the sharpness of an image. Images can be over-sharpened and appear ‘pixilated’. Photoshop has a filter called “Unsharp Mask” with an infinite number of options for sharpening. I found that using grainy film wreaks havoc on the image if over-sharpened. Sharpening works by Photoshop “looking for a difference in tone” and increasing the difference. At the risk of sounding technical, I’ll just say that over-sharpening can make Photoshop ‘draw’ a white circle around each spot of grain.
With curves and sharpening ‘conquered’, I have made successful images from “Desktop Negatives”.
Showing are the contrast curves I created which I applied to the final image just before sending it to the printer. Note: each vertical line in the grid represents10% with the left edge being 100% and the right edge being 0%. Different inkjet printers will print negatives differently. This new curve for my Epson Stylus 2200 is different than the one Dan Burkholder created when he tested an Epson 2200. Also I discovered that the contrast curve works differently if applied to an RGB image than when applied to a grayscale image. You will have to create your own curves for your images. These and the Curves included in Dan’s book are just a starting point. Enjoy!
*Making Digital Negatives for Contact Printing Second Edition by Dan Burkholder is published by Bladed Iris Press ISBN#0-9649638-6-8 It includes a CD with step tablets and ‘starting point’ curves.