With a film camera you can use colour slide film or colour negative film - both of
which are developed in a darkroom in a different set of chemicals.
Cross-processing happens when one type of film is developed in the others’ chemicals.
What does a cross-processed image look like?
Luckily, there are so many different combinations of film, paper and chemicals that
the end result can vary immensely.
Common characteristics of a cross-processed image include:
high contrast, colour shifts, blown-out yellowy-green highlights and navy blue shadows
– which doesn’t sound very appealing – but I quite like it :)
Open up your Layers Palette and make a copy of your photo.
Click on the adjustment layer icon and select curves.
This is how we are going to simulate the weird colours and blown-out highlights.
When the curves box opens up, ignore the RGB channel – we aren’t going to touch it.
Instead, click on the drop-down ‘Channel’ menu and select ‘Red’
Create an ‘S’ curve.
When you create an ‘S’ curve, you are dragging up the highlights and dragging down
the shadows – resulting in a higher contrast image.
Go back to the ‘Channel’ menu and select the green channel.
Create another ‘S’ curve.
Select the blue channel and clip the highlights and shadows of the curve as shown.
The curves don’t have to look exactly like mine – you can fiddle with each one until
the image looks pleasing.
The image probably looks a bit flat – so create another curves adjustment layer –
this time with the blending mode set to ‘Luminosity’ (so that we will only alter
the contrast in the image and not change the colours).
Create another shallow ‘S’ curve to increase the contrast.
Fiddle with the opacity of the layer until you’re happy the effect isn’t too overpowering.
Just to finish off, I changed the blending mode of my copy layer to ‘Soft Light’
and reduced the opacity to 40%
Using ‘Overlay’ created a nice effect too – I always just scroll through them, and
use the one that gives the most pleasing effect to the image.