We participated in Impact 5 printmaking conference in Tallinn, Estonia on 17-20 October. The Impact conference is an international forum for printmakers, curators, critics, collectors and suppliers of art printing materials and presses. The conference is held every second year in the autumn, this year in Tallinn.
At the same time there was the 14th International Tallinn Print Triennial taking place, so there were plenty of lectures, panels, technical demonstrations, exhibitions, and portfolio presentations going on in Tallinn Old Town and at Kumu Art Museum.
Correction curves for hand sensitized contact printing processes normally look like inverted S-shapes in Photoshop, meaning they tend to flatten image contrast. As an exercise we tried to build a correction curve for standard RC silver paper (Kodak Polymax RC II). In the final print the tone range is clearly better with the correction curve, but we need to print also some Â“real worldÂ” pictures later to see if we need some further adjustments.
An example of how the correction looks after plotting the curve for Polymax II RC paper, using the Epson R1800 to print the negative. The test image looks very flat after correction, but the curve definitely improves tone separation in the contact print.
We also tried to build correction curves for MACO Black Magic liquid silver emulsion, but resulting from roughness of the paper, it was hard to measure the test print accurately with a scanner. And a different story is the trouble with coating any paper evenly with the emulsion, thereÂ’s a lot to learn about that. WeÂ’ll be returning to this topic laterÂ…
Two quick tests with MACO liquid emulsion. They are slightly overexposed, but you can see that the emulsion is quite contrasty (although it’s VC (variable contrast), and we used the lowest grade (#0) filtration). The left test was exposed on a single coated, and the right one on a double coated paper. The paper (Arches Aquarelle) was too textured for this test – it is hard to find even areas of tones for density readings.
When making digital negatives we have ended up using two different methods. Quite straightforward and simple way with inkjet printers is to let the printer render the grayscale image using all inks. These transparencies are easy to read and evaluate, and corrections to the tone scale can be done with effortless and straightforward thinking. This method usually seems to suit art students well – they want quick results and donÂ’t care to make the matter too scientific. ðŸ˜‰
The easiest way to make a digital negative is to print the image file, converted to grayscale and inverted to negative, onto suitable transparency material. It is also the fastest way, but the final result will not necessarily be very good, because the tone range of the original image will distort somewhat when the neg is contact printed, depending on the contact printing process used, and you will need a method for correcting the tone scale. Usually you can make corrections using a correction curve attached to the image file in Adobe Photoshop. Actually the correction curve should be built for every combination of printing process, printing paper, developer, and other variables occurring in the printing process.
We have started building correction curves in Photoshop in a simple way: by printing a digital negative with known gray tones on transparency, printing the negative with some standardized contact printing method (common silver print, cyanotype), measuring the print’s tone range distortion with a scanner or densitometer, building a correction curve to remove the distortion, and finally printing a new, corrected negative. We are printing with the Epson R1800 and Pro 3800, the transparency material is Agfa CopyJet film.
The purpose is to remove guesswork from exposing hand sensitized materials, so that with using proper correction curves we could easily produce Â“perfect printsÂ” without too many tests.
This entire method is described very well in Digital Negatives, a book by Ron Reeder and Brad Hinkel. In fact we have used the step tablet image downloaded from the authorsÂ’ website in making our own correction curves.
We will post here some pictures of our curves and tests later.