Category: the Lab

Ilford PanF as Lab-film

Posted on Posted in dye transfer, exs notebook, labnotes, the Lab

pulling a camera film into the darkroom to become a lab-film

Don’t fall for the “curve” bull; most film can be useful as a lab film. Always was. For most of the life of photography, film has been meant for use in a camera. Specialized process, specific to color printing, called upon the skills of emulsion makers to ease the task of color production.

It isn’t unusual to make masks of differing density ranges to modify different portions of the original’s curve. The lab film list from 1970 era would have been:

  • Kodak Pan Masking Film 4570, which had no anti-halation backing, making it near perfect for unsharp masks
  • Kodalith Pan Film 2568 which had a very steep curve. This was controlled using the “Ds” D-19, D-11,D-8 (not Ilford ID-11)

The following is updated from an Ilford Cibachrome datasheet, which anyone using the product should have noticed.

The difference between those who ride and those who shovel.

The exposure layout, using enlarger as light source.

A: Light (Enlarger set to height for projecting a 35mm to 8×10 size). Lens at f/16. First trial exposure for 10 seconds.

C: Glass to hold the Original in close contact with the un-exposed PanF (mask to be)

D: the Original (chrome) facing emulsion down (away from light)

E: is the PanF film — emulsion side up.

F: BLACK backing paper – reduces flare

G: baseboard. I use smooth black-rubber sheet from electronics supply houses.

3M silver tape aids in placement of “curly” PanF film. Small spots work well.

Developer: Ilford PQ Universal [1:20] 68F, 3 minutes tray agitation (constant)

Alternate: DK-50 [1:4] instead of the PQ Universal.

If the development time is too short, or if the film has a warmtone tint, add Benzotriazole (BZT) solution to the developer (either PQ or DK) . An initial point: 10ml of 1% BZT to 300ml of working developer (tray)

BZT solution must be mixed at125F, otherwise the powder won’t dissolve. You can also buy prepared anti-fogs from Bellini, or Moersch.

According to Kodak’s “Processing Chemicals and Formulas for Black and White Photography”, publication J-1 1973, Kodak Developer D-19 is designed as a higher contrast developer for continuous tone films. It provides short development times. While primarily aimed at scientific applications, it has utility where high contrast is desired.

It is not as active as D-8’s extremely high contrast or D-11’s very high contrast. Both of those are designed to fully utilize the line reproduction possibilities of lith films. Kodak says D-19 produces, “brilliant negatives with short development times. It has good keeping properties and high capacity. D-19 is recommended especially for continuous-tone work that requires higher-than-normal contrast.”

Making Grey

Posted on Posted in dye transfer, overnight notes, the Lab, Theory

Principles of color photography.

neutrals

Selective and nonselective neutrals– a foundation concept in the technology of color photography. The illustration that we have many paths to grey, none of them is the perfect path. For any decision about a colorant (dye or pigment) we must consider more than making a neutral, even a set of dyes making a neutral results in different color volume. This is the why a film looks different: the relationships among the real color and the created color. Industry chooses the colors that they can sell. Old texts, as well as the experiments, remain useful, valid today. They form the foundation. Those equations are accurate — math has a way of doing that.

The means to the solution. The tools of presenting or testing, examining the experiments have changed drastically since the foundation years. We can readily present to others results they couldn’t imagine. That has changed the learning, not the theory.

we can easily compare gamuts using at hand Apple tools. this color cube is what a set of balanced Kodak dyes from dye transfer (1985) covers compared to the background cube of an HP Z printer on glossy baryta paper from 2015.

Clearly, implementation of the theory has advanced.

dye transfer color inset into HP inkjet

Key names: Evans, Friedman, Spencer, Wall.

  • R. Burnham, “Visual Selection of Color Film Neutrals,” J. Opt. Soc. Am. 48, 215-224 (1958).
  • W. Brewer, W. Hanson, and C. Horton, “Subtractive Color Reproduction. The Approximate Reproduction of Selected Colors*,” J. Opt. Soc. Am. 39, 924-927 (1949).
  • Wall, History of Three-Color Photography
  • Friedman, History of color photography,
  • Spencer, Colour photography in practice
  • Evans, Principles of Color Photography