Gimp Tutorial- Cross Processing

In the film world, cross-processing is developing color print or slide film in the wrong chemicals — for example, color negative film in slide chemicals ("C-41 as E-6") or slide film by the color negative process ("E-6 as C-41"). This causes wild color and contrast shifts and requires lots of trial and error and were very much in vogue for a period in the 1980s and 1990s.

With many possible permutations of film stock and processing techniques, there is no single, identifiable, cross-processed appearance. The most common combination is C-41 as E-6, in which slide chemistry is used to process color negative film, and it's a quick job to imitate it in Gimp. Image contrast is usually high with blown-out highlights, while the shadows tend toward dense shades of blue. Reds tend to be magenta, lips almost purple, and highlights normally have a yellow-green color cast.

As for subject matter, fashion and portraiture are the most common, but you should not allow your imagination to be constricted by the "standard practice". Experiment with this technique and have fun!

1. First, open up your image in Gimp. Go to Colors>Curves.

2. Access the different color curves in the curves window and change each curve to the following:

(Select the Red channel and drag the top right of the curve a little to the left. Then drag a couple of points on the curve so that it forms a very gentle S — darkening the shadows and brightening the Red channel's highlights.)


(In the Green channel, add another gentle S curve — increasing the contrast, especially in the highlights.)


(Select the Blue channel and drag the curve's top-right point downward. It doesn't need to be much — just enough to take some blue out of the highlights. Then drag the curve's bottom-right point up a little, blocking up the Blue channel in the shadows.)

TIP:
To save your curve to a file on your hard drive, just click the Save button. Applying the same cross-processing adjustment to other images is a simple matter of loading it with the Load button in the Curves dialog box.

3. While I liked the look of my image after adjusting the color curves, I felt like it needed just a little more contrast. *Use this step at your own discretion.* Go to Colors>Levels.

(I slid the black levels slider- circled in red- over some to the right. It wasn't a drastic change but it did create a noticeable change in contrast.)

So there you have it. Cross processing the Gimp way!