Re-defining the Digital Negative

The fact is that the negatives produced by editing programs are unusable, but instead of investigating why the negative doesn’t work and coming up with a solution, an entire industry of videos, websites, and sometimes confusing advice has developed on how to fix the problem of the unusable negative.  

The cause of this problem is the fundamental difference between digital and analogue prints. Analogue alternative process prints respond according to the H&D DLogE curve and require logarithmic negatives; editing programs use linear colour scales and percentages, and creating negatives using RGB or Lab colour scales from a spectrophotometer is like trying to fit a square peg into a round hole.

This conflict can be resolved by using logarithms, because the negative and positive logarithms of the digital image are inversely proportional.  This means that a 16-bit analogue-to-digital negative can be calculated using a Python-based data processing program, completely eliminating the need for densitometers, scanners, linearization procedures, etc.

TruNeg manages the various alternative processes by creating profiles. They map the difference between the calculated negative and the negative that produces a good print found using test strips and adjusting the negative. The profile is loaded into the app during contrast calibration.

Profiles can be accessed for free on the TruNeg website for Argyrotype, Carbon/Gum Bichromate (A. Dich.), Classic Cyanotype, Salt and Van Dylke Brown. A generic profile is available to assist in making profiles for unlisted processes.

The application generates an interactive plot that allows the user to fine-tune the print using traditional test strips. While some experience is required, there is nothing to stop the relative newcomer from producing high quality prints after two or three test strips.