TECHNICAL AND SERVICE INFORMATION
AgX Imaging Film Processing Advantages
AgX Imaging is absolutely committed to excellent film processing and scanning. The service that AgX Imaging provides to its customers can be summed up in three words, “Attention to Details”. As you will realize while reading through this material, no corners were cut. There are no secrets to film processing; it just comes down to executing the commitment to quality. A commitment to quality is not easy, it takes more time, it’s harder to implement and sustain, but it’s absolutely the way to provide unparalleled quality.
In my opinion, a photographic image cannot reach its full potential until three criteria are achieved. These are: a visually interesting scene, proper exposure, and precise reproducible processing (whether chemical or digital). If any one of these three criteria is not achieved, the image will never reach its full potential.
Below is a list of advantages that photographers will gain by processing film at AgX Imaging followed by a detail explanation of these advantages.
Optimized Dye Stability of Films
The dye stability of films is optimized when chemical stabilization is provided, and all residual chemicals and metallic silver are both completely removed from the emulsions. “The Theory of the Photographic”, edited by T.H James states that retained thiosulfate, from fixer solutions, can cause dye loss during keeping. “The Permanence and Care of Color Photographs”, by Henry Wilhelm, states that “decreased dye stability and or higher stain levels may be expected with improperly replenished or contaminated processing chemicals, omission of recommended stabilizing solution, and inadequate washing”. Residual thiosulfate encourages dye loss, while residual levels of silver metal result in desaturation of colors and increased highlight stain. Improper stabilization dramatically decreases dye stability resulting in serious dye loss.
AgX Imaging utilizes pure water washes at the end of the process to insure that all residual chemicals are completely removed. The use of two fixer tanks, both agitated by non-oxidizing nitrogen gas, insures complete removal of all metallic silver from the film emulsion. Finally, AgX imaging uses Kodak Process E-6 chemicals which allow for dye stabilization to occur half-way through the process instead the end of the process where other chemical manufactures place it. Stabilization of films at the end of the process can certainly be accomplished properly; the problem occurs when most labs need to dilute this solution in an attempt to reduce streaking and water marks or formaldehyde fumes from the stabilizers. Dilution of the stabilizer and thus the formaldehyde directly decreases long term dye stability. If you not planning on keeping the film for a long period of time then this is not a concern.
Increased Process Uniformity
Process uniformity refers to the ability of the photographic process to develop all surfaces areas of the film at the same rate insuring there are no color, density, and contrast changes throughout the entire roll or sheet. Process uniformity is affected by agitation, recirculation, stratification of solutions, and film transport speed.
Agitation of film in “Dip and Dunk” or “Rack and Tank” processors is accomplished with bursts of pressurized gas distributed from the bottom of the processing tanks using distribution bars known as plenums or spargers. We utilize plenums on the bottom of each tank in addition to plenums on the side walls of both the First and Color Developer solutions thus optimizing process uniformity across the film surface. These added plenums become easily apparent as the film format increases from 35mm up through 8×10 inch sheet film.
Recirculation is achieved through the use of pumps. Solution recirculation serves four main purposes. First it keeps solutions well mixed so there are no chemical differences throughout the tank. Without recirculation heavier chemicals would fall to the bottom of the tanks producing higher chemical concentrations at the bottom and lower levels at the top. Secondly, recirculation helps to keep critical temperatures even through the tank solution. Third, recirculation also serves as a weak form of agitation, where good even recirculation can smooth out strong agitation patterns. Finally, recirculation allows for filtration of solutions to remove development by products and dirt particles.
Solution stratification is a result of differing levels of temperature or specific gravity throughout the tank solution. Stratification in the Reversal, Pre-Bleach and Final Rinse produce different affects. Stratification in the Reversal solution can cause color shifts between the top and bottom of the tank. In the Pre-Bleach solution, films located near the bottom of the tank will be better stabilized than near the top. In the final rinse, film near the bottom of the tank will likely develop more streaking problems then those located near the top.
The Reversal, Pre-Bleach, and Final Rinse solutions easily oxidize, which is why labs do not recirculate these solutions. AgX Imaging is able to recirculate these solutions for small periods of time at regular intervals throughout the course of film processing. The result is no stratification and oxidation of solutions. A seemingly easy solution, though it took several months to figure out the proper balance of on and off times. This is why we recirculate these three solutions on a timed basis.
Film transport speed determines the total time from when the film exits one tank and enters into the next tank. The film images located near the bottom of a rack enter into any given tank first and leave last. In affect, the film at the bottom of a film hanger/rack has more time in each solution than those near the top. At AgX Imaging, our film processor uses three phase transport motors allowing us to safely increase the transport speed between each tank. Having this ability virtually eliminates the differences between the top and bottom of each hanger/rack.