Platinum, Polymer Photogravure and 3-Colour Gum Dichromate are all contact processes that require negatives or positives the same size as the final image. The easiest and most cost effective way to make them today is digitally and depending on the final process or size of print, I use either an imagesetter ( for gum dichromate separations) or Epson inkjet printers (for platinum negatives and photogravure positives).
Over 90% of my personal work is still shot on film although much of the work that I print for other photographers is now from digital files. Whether an image starts as a film negative or as a digital file, the print processes I use all require either a negative or positive the same size as the final print. Platinum and 3-colour gum dichromate both require a film negative and polymer photogravure a film positive.
Making these inter-negatives and positives would have previously been very time-consuming and necessitated using film, an enlarger and chemicals in a darkroom. This method involved much testing to get a good negative. Eventually, many of the films that were suitable were discontinued or else became prohibitively expensive to buy. So for many years now I have made them digitally, affording me greater control over the contrast adjustments needed for these processes.Once the film has been scanned, the image is edited in Photoshop using many of the methods I would have used in the darkroom in the past - burning, dodging, cropping etc. Like many photographers and printers working with these processes I’m using an inkjet printer to make the final film. I output the file to clear film using an Epson printer, Quadtone RIP and Pictorico OHP (overhead projection film) which produces a contact negative, or positive, depending on the process, that can be printed in the darkroom. For the 3-colour gum dichromate prints I usually work from separations output using an imagesetter. These can be successfully made using inkjet negatives, but the large image size that I'm working with dictates that I use imagesetter output. Before the final film is made, the image has to be adjusted to compensate for any differences in tonal range between the printer and the printing process. For the platinum and photogravure film I do this by controlling the printer driver and the amount of ink it puts down using RIP software. With the colour separations for gum dichromate I convert the image from the Adobe RGB colour space to a custom profile made specifically for this process, the paper and the pigments I use. This allows me to soft proof the image and obtain a more realistic view on the monitor of how it will appear on paper when printed in gum.