The term “cross-processing” sounds very technical and abstract. However, the technique to manipulate your images digitally as if they were cross-processed is very easy. But what is cross-processing actually?
Cross-processing, briefly, is a photographic technique where slide film (E6) is processed in the set of chemicals usually used to process print film (C41). The result is images with oddly skewed colors (usually with a cyan hue) and increased contrast and saturation because the high-contrast slides have to be enlarged on a paper which is actually intended for print films with less contrast.
Less common is cross-processing in the other direction–print film processed in slide film chemicals. The result you get then is lifeless images in subdued colors because the chemicals intended for slide films compress the lights on the already low-contrast print films. Moreover, you can never be sure what colors you will actually get.
The film material is extremely and irreversibly modified due to the cross-processing technique; therefore, the advantages of the digital cross-processing simulation are obvious. And the key for digital cross-processing is the modification of the curves.
Process a print film like a slide film (I will explain for Photoshop CS 2 here)
1. Open the picture you want to process.
2. Press Ctrl+M to open the curves window or click on Image > Adjustments > Curves.
3. Modify the curves for RGB and all channels (red, blue, green) as shown in the pictures below:
4. The curves here are only for a start, and you will probably have to re-adjust the curves (especially the standard-RGB curve) until you get a decent result. This technique is interesting especially for portraits.
Process a slide film like a print film
1. Basically, it’s the same technique as shown above. Open your image and adjust the curves like this:
2. Same for these curves: They are only a start; you will probably have to slightly tweak them to satisfy your needs.
3. Don’t worry about the brightness too much. Just play around with the curves and focus on the contrast and colors first. After finishing the curves, adjust the levels (Ctrl+L) and make your picture brighter by sliding the small right arrow below the histogram a bit to the left.