Ryan Little and Professor Tom Lefler, Theatre and Media Arts

As a student of cinematography I have focused most of my studies on “Sensitometry,” the science of measuring the response of photographic emulsions to light. The way in which a film is exposed, processed and viewed can affect the degree to which the film=s sensito-metric and image structure potential is realized. Knowing what a film is designed to do is an absolute necessity for any serious cinematographer.

One very valuable step in gaining a comprehensive understanding of film emulsions is to study the developing stage, which is what my research was centered around. I started by testing a reversal film stock as well as negative film stock. In my tests I studied two different developing techniques, one is known as Cross Processing and the other is know as Bleach bypass. Both of these techniques can be used to create a varied look of a film print. These experiments were conducted over a period of one week. During this research project I examined how the grain structure of a given film stock looked when it was processed in an opposing developer. I took film negative and exposed it to varies color temperature of light. The temperatures ranged from 3200 kelvin to 5600 kelvin. After exposing the film I then use a ENR process to develop it. I tested two different film stocks, one was color balanced for daylight (Kodak Vision 250D) and the other was balanced for tungsten light (Kodak 7240).

I discovered that when you cross process film the colors shift drastically. By shooting a reversal film stock (kodak 7240) and running it through a negative film bath, a new hybrid film negative is created. This new color palette is unique, resulting in very saturated and vibrant colors. With these kinds of results one would have to wonder what would happen to skin tones. It became immediately apparent that when exposed at the correct color temperature, which in this case was 3200 Kelvin, that the color shift was towards more warmer tones (1800 Kelvin). It was immediately apparent that the grain structure was enhanced and the visual image had more texture. In an attempt to correct for the skin tones I decided to use 5200 daylight balanced lights, which brought the skin tones back to a more normal level of saturation and color. I also observed that the exposure curve of the cross processed film had become more steep. It had increased in contrast in the negative. When something in the image was in shadow the fall off into black (the toe of the exposure) was immediate. The blacks in the film were like ink, very rick and dense.

With the daylight balanced film the results were less pleasing. When a negative film is put through a reversal stock developer it does not become a reversal film, as was such with the kodak 7240 reversal film which became a negative film after developing it in the negative bath. The look of the daylight film was very low contrast, more pastel in color. The image had a strong haze appearance to it as well as the image looked faded. The colors were muted and washed out. Changing the color temperature did not increase the contrast or improve the color saturation of the film.

The second part of the research was to do a Bleach Bypass in the developing stage. This was done by not allowing the latent image (exposed film before the developing process) to be introduced into the bleach tank of the processing proceeder. When doing this I discovered that the film increased in contrast as well as lost in the highlights. The shadow areas of the negative became very thick much like the reversal film that had been cross processed. The bleach bypass did not affect the color pallet of the film except to slightly reduce the radiance of bright colors such as red. The film stock retains much more of its silver particles than from a normal negative which is the reason for the density in the black areas (shadows) of print.

There is very little written material on either of these types of developing processes. I have looked extensively through many journals on sensitometry and cinematography and have only found vague material. I feel that through this research project I now have a better understanding the limits of a film negative. This knowledge has aided me in my goal of becoming a professional cinematographer. I feel this information can be useful to other cinematographer to aid them in understanding the workings of the film negative.