When kicking around ideas of different uses for ImagOn polymer film we decided to try it at printing photographs that were screened in Photoshop. You can find info on this topic and the vast possibilities of ImagOn in Keith Howard‘s books Non-toxic Intaglio Printmaking and The Contemporary Printmaker: Intaglio-Type & Acrylic Resist Etching.

Here we have a quick experiment; we first created a tone compensation curve, and then applied it to any grayscale image to be screened and converted to bitmat mode for outputting to an inkjet printer.

An ImagOn test print and a plate. Note the open bite that occurs at the darkest tones – the screen frequency is too high, or the printer is outputting too much ink (for this purpose) so the light cannot pass during the exposure.

The curve can be created for halftone screened images as well as for continuous tones (again ChartThrob does a good job here), but when using ImagOn and inkjet technique we tend to clip the tones somewhat, especially at the dark end of the range.

Our curve for Andromeda’s EtchTone screen at 85 lpi frequency. The curve is very straight, it is messed up by open bite at the darkest tones. Actually the curve we finally used was adjusted by just straightening it to the left edge (the gray line).

Besides Photoshop’s own (actually quite good) dithering methods there are other software tools for screening images. Some of them work as Photoshop plug-ins, accessible from the filter menu, for instance.

Enlarged portion of a bitmap image showing the EtchTone’s SteelEtch screen.

Depending on the chosen screening technique, the outcome can be finely dotted screen, almost invisible to the naked eye, or coarse special effect, breaking the image surface down to larger dots. We tried Andromeda Software‘s EtchTone plug-in (among others), finding it quite interesting but hard to control – with the inkjet technique and our line frequencies we couldn’t get rid of posterization, which showed annoyingly especially on some tone gradients.

An ImagOn print from a plate exposed through a screen film positive. Notice the heavy posterization in the sky area.

We are done with testing ImagOn and other polymer plates for now – some of the students are experimenting on their own – maybe we will hear from them some day…