Cross-processing Tutorial

Cross-processing is developing colour print or slide film in the wrong chemicals. This causes wild colour and contrast shifts and requires lots of trial and error. The most common combination is C-41 as E-6, in which slide chemistry is used to process colour negative film, and it's a quick job to imitate it in Photoshop. 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 colour cast. As for subject matter, try portraiture - the skin tones and red lipstick look especially striking in cross-processed images, but there's no need to restrict your imagination.

STEP 1
With the original image open, click the "Create new fill or new adjustment layer" icon in the Layers panel and select Curves. From the Channel drop-down box, 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.
TIP
To save the 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.

STEP 2
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.

STEP 3
In the Green channel, add another gentle S curve — increasing the contrast, especially in the highlights.

STEP 4
Fine-tune the channel curves to suit your image, but leave the combined RGB curve untouched. Focus on the colour balance rather than the contrast, which you can fix later, in step 6.

STEP 5
Blown highlights are a common — if not always welcome — characteristic of C-41 as E-6 cross-processing. They should result from the contrast-increasing curves used in steps 1–3, but in Photoshop it's possible to eliminate them if you wish. Try changing the Curves adjustment layer's blending mode to Colour and the image will combine the colour shifts with the image's original luminosity.

STEP 6
If you need to fine-tune the image contrast, add a Curves adjustment layer and set its blending mode to Luminosity so it doesn't cause any further colour shifts.

STEP 7
Another optional final step is to add a yellow colour cast to the picture.
In the Layers panel, click the "Create new fill or new adjustment layer" icon and choose Solid Colour. Select a yellow-green and click OK, then reduce the new layer's opacity — 10% is as much as you'll need.

Try it out and have fun!