Cross Processing involves running a film through a process for which it wasn’t designed or tested. An example might be running Color Reversal Film through a camera negative process (C-41) instead of through the color reversal process (E6) for which it was designed.

Camera reversal film uses a different development process from camera negative films and yields a positive image that can be directly projected without the need of a print. The key to the reversal process lies in the two-stage development of the image. This unique process uses both a B&W developer and a color developer.

Light areas of the subject end up transparent on the film, and similarly, dark subject areas build up greater densities on the film and are more opaque. Thus, the reversal process maintains the relative brightness values of the original scene, and a positive dye image is formed.

For camera reversal film, what you expose, is what you get! Therefore, there is no orange mask incorporated into the film’s design and there is very little latitude. If the film is underexposed, the B&W developer will form an image with low density. Then in the second stage of development, the film will go through the color developer; the result will be a final underexposed image which will be very dark. Conversely, overexposures will be very light. Using camera reversal requires a very good exposure to get a good result.

Sensitometric Curve of Ektachrome 100 in E-6 process

When running camera reversal film through the C-41 (camera negative) process, the most obvious difference is that a negative image is formed. Camera reversal film was designed for a specific process with an appropriate exposure index. By processing reversal through a non-standard process, the actual speed of the film is not known. Therefore, it is strongly recommended that exposure tests be performed to ascertain what the exposure level of the film should be through the lab’s process.
Secondly, the film’s design was based upon running it through an E-6 (reversal) process, which will give it a projection contrast of around 1.6. If it’s run through non-standard process, the contrast is unknown.
A final consequence of using a non-standard process is the impact upon color rendition. Although both the E-6 process and the C-41 use the same color developer, the films themselves have different color couplers and colors reproduce differently along with mismatched color contrasts.
It is also likely that cross processing results will vary from one laboratory to the next. Therefore, discussion with the laboratory should take place and tests should be run to make sure that the ‘desired look’ of the final image will be achieved. And then use the same lab for all your cross processing – don’t switch to someone else and expect to see the same results.

Pictorially, a camera reversal film that was run through an C-41 process and then printed onto photo paper will have:

  1. Higher contrast – the slope of the curve would be higher producing more contrast or harshness in flesh tones; a good lighting ratio of 4:1 would result in a harsher-appearing image because of the processing. Higher contrast may result in clipped highlights and shadows.
  2. Higher color saturation – would occur in certain colors and would produce a different ‘look’.
  3. Some colors would be distorted and over-saturated. A word of caution. Cross processing changes will be different for different films or for different colors. Color are not as faithfully reproduced as would be the case if the film has been processed as recommended.
Left: Color Negative in C41, Right: Color Reversal in C-41

The image on the left has much more uniform contrast particularly noticeable in the African-American and Caucasian flesh tones. The gray background and vivid colors are realistically reproduced. The image on the right has much higher contrast particularly evident in the harsh flesh tones. The background, the woman’s jeans, and several colors in the women’s sweaters show color saturation and distortion.

Left: Color Negative in C41, Right: Color Reversal in C-41

This is another example of the effects of cross processing. The image on the left is Color Negative Film processed as specified through C-41 process, and printed out. The image on the right is Color Reversal Film, cross processed through C-41 process also printed out. The image on the left has much more uniform contrast and the colors are realistically reproduced.
The image on the right has much higher contrast and the colors are saturated and distorted.

As cross processing is a non-standardized processing for film, the result cannot be guaranteed.

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