The terms "skip bleach", "bleach bypass", "ENR", etc, refer to a number of related proprietary processing techniques currently being offered by some motion picture laboratories as a means of increasing contrast, darkening shadows and reducing the color saturation of images. Since these techniques represent departures from normal recommended practices, Eastman Kodak Company has been asked to comment on their use by laboratories.
Whereas skip-bleach techniques may sometimes give desirable results from a creative perspective, Eastman Kodak Company cannot guarantee product performance nor assume any responsibility or liability for its products when they are processed under non standard conditions.
A number of related processing techniques currently experiencing some popularity in the motion picture industry are called "skip-bleach", "bleach bypass", "ENR", etc. These techniques are employed in certain film productions to create special looks or moods. They are accomplished by a variety of techniques which allow some or all of the image silver, which is normally removed by bleaching and fixing, to be retained in the film along with the image dyes. The retained silver increases the contrast of the image and decreases the color saturation by adding gray or black to the dye images. Skip-bleach techniques can be applied to the processing of the camera original negative, the intermediate positive (IP), duplicate negative (DN) or final print, or any combination of these stages.
Different results are achieved according to which step the skip-bleach technique is applied. When applied to an original negative, the effect seen on a print made from the negative results in lighter and possibly blown-out highlights, higher contrast and perhaps higher graininess. When applied to the print, the effects are mainly seen in the shadows, which will be darker, richer, with higher contrast, less detail (possibly blocked-in) and with desaturated, muted colors. These effects can be very scene-dependent.
There is a common belief that if a skip-bleach technique is used with camera original film and is later determined to be unsatisfactory, the film can simply be reprocessed normally to restore its integrity. Reprocessing of camera original film places it at risk because of extra handling and should be done only as a last resort. In addition, if any allowances were made for skip-bleach in the exposure of the film, such as underexposure or the use of flat lighting to compensate for the increased density and contrast caused by the retained silver, then reprocessing to remove the retained silver will produce a thin, underexposed "flat" negative with smoky shadows and possibly higher grain.
Skip-bleach techniques will affect film sensitometry, tone reproduction, shadow and highlight quality and color saturation, as well as process control, LAD values, telecine transfer performance, film handling properties, heat absorption during printing and projection, and dye stability.