Digital Negative
Example of palette ready to be printed and used to determine the characteristic response curve of a cyanotype print on Schoeller Durex Satin paper.

The majority of alternative prints and historical processes require negatives of the same size of the final image. Photographers that use mammoth cameras can obtain them directly en prise de vue, while others must enlarge their negatives to obtain the desired image. There’s plenty of analogical techniques that produces negatives adapt for each alternative technique, but digital negatives printed on transparent films are getting more and more common.

The result is a cocktail between chemical photography that is 150-years-old and the most modern digital technologies. A good way to close the circle.

Guides, manuals, articles and tutorials

The most complete and meticulous guide, reference point about digital negatives since a couple of years, surely is Precision digital negatives (PDN for the rest of the article) by Mark Nelson. The site doesn’t give any information, but an e-book is to be bought, for around 80 euros.

I personally think it is quite expensive. The book is redounding, it could be reduced to a quarter, it is terribly pedagogical and pedant, deeply American. But after all, PDN surely is an essential reading. It is the base and the first work that accurately formalized the procedure to obtain digital negatives. It can be resumed in three steps:

  • Determination of the reference exposure time, the exact time to gain d-max of a certain process. It fixes the black point of the print.
  • Determination of the negative color, who will give back a pure white after an exposure equal to the reference time. This procedure fixes the white point of the print.
  • Determination of the characteristic curve of the process. This linearizes the answer of the print between black and white point fixed before.

Damiano Bianca came to similar PDN conclusions in his wonderful italian article Negativi digitali inkjet.

As I do, Damiano Bianca uses a method derived from the three PDN steps and with the help of a useful automatized instrument: the Chart Throb that speed the generation of the response curve necessary to produce digital negatives.

Talking about the process I use, it is quite the same Michael Koch-Schulte describes in his Quick Guide to Making Digital Negatives. Moreover his website contains the interesting article The RNP-Array System, which explores the influence on digital negatives of different color space models.

Those informations help you produce the best digital negatives you can produce nowadays. There are some more websites that, even if they are not really up to date, deserve a reading.

Digital negatives precursor surely is Dan Burkholder, even if he doesn’t use colored negatives. Jeffrey D. Mathias’ Guide to Platinum Palladium Photographic Printmaking contains tons of informations about platinum and palladium prints and also includes a part on digital negatives. This last describes completely different methods compared to PDN, often using several overlapped and registered negative. Ron Reeder is another printer of this prestigious technique; he wrote a wonderful chapter on digital negatives in his guide Pigmented Platinum Manual. Alternative photography proposes many articles about the preparation of digital and analogical negatives for alternative techniques. Last but not least, there’s a famous introduction on Unblinkingeye by Gary Nored inside Making Digital Negatives for Van Dyke Browns.

Where to buy digital negative materials

Pictorico OHP films, the most common in overseas literature, are sold in Europe by Nova darkroom. A similar but cheaper alternative is Agfa Copyjet films, sold by Lotus View Camera in Austria and by Tiflex in France.

Transmission palettes to determine reference time, practically indispensable, are sold by Stouffer. T3110 is the most used, but also the less accurate T2115 is good.