Solarisation is the effect whereby the properties of a material is affected by electromagnetic radiation.

It’s effects in photography were first discribed in 1859 by H. de la Blanchere and usually refer to the skewed tones which result from exposing an already exposed (used) film to light before or during processing. This effect was popularised in the 1920’s by American painter and phtographer Man Ray.

I saw Photoshop intructions for how to reproduce this effect digitally in a UK photo magazine (can’t remember which one, sorry), so all I had to do was GIMPify these intstructions.

A word of warning, this effect can look good on some images but just doesn’t work at all on others. Image selection is important and you may have to try this effect on a few different images to get one which “works”. The guy in the print shop thought I was crazy when he seen this image first, but he changed his mind once he saw the enlarged print.

1. I started with a photo of a neighbours 1931 Norton. The first thing we do is to desaturate the original image by selecting “Colors” > “Desaturate” from the dropdown menu. I have chosen to do this using the “Average” option.

2. To replicate the skewed tones characteristic of solarisation we need to produce a radical inverted “vee” tone curve, (GIMP shows its class here, as not all applications give sufficient control over the tone curve to replicate this effect). We have two options to create the inverted “vee” curve, a.) we can use the freehand mode, which can give a good, if somewhat wobbly curve. b.) the method I prefer as outlined here. Launch the “Curves” dialog from “Colors” > “Curves” and leave it on the default “Smooth” curve type. Grab the centre of the curve (straight line as yet) and drag it up to the top of the window.

3. Next grab the right hand end of the curve and drag it down to the bottom of the window.


4. Next gab a point on the curve near the top/apex/crest and drag it up and over so it is just beside the topmost point of the curve (I say just beside as two points cannot live at the same place, your top point will have an X coordinate of about 127, so aim to place your new one just beside it at 126 or 128 depending of whether you are dragging from left to right or right to left). Viola one inverted “vee” Solarisation type curve.

You may wish to launch the “Curves” dialog again and do some fine tuning, a gentle “S” curve often works well, I did not feel that it was necessary for this image. Be sure to try this effect out on some portraits, it can really emphasise the eyes and give a very aluminum “Metropolis” type feel as you can see in this photo of my cousins kid.

Happy GIMPin’,