I stumbled upon ‘Retinex’ filter which is available free in GIMP. Retinex is a theory, developed in 1971 by E. H. Land, and deals with human color perception under varying lighting conditions. Regardless of the theory, I tried it to boot contrast and details in images. The out come is dramatic and I thought to share the experience.
1. The base image, of my younger brother:
The image is not bad to begin with. But I want to increase contrast and details.
2. Duplicate the layer. In the copy layer (call it ret), run the Retinex filter with the default values. This gives the following image:
The effect is dramatic and in this case too intense. Occasionally this is all an image may need. To mellow it down,
3. Change the blend mode of ‘ret’ layer to overlay and set the opacity to 50% to get
You can change the opacity level to control the effect. 50% usually will work for majority of the images.
That is it. The above may be taken as the final image. although many other techniques can be mixed.
My interest, however, is to get a punchy black and white image.
4. Flatten the image, convert to black and white. I used channel mixer red=31, green=36 and blue=33 settings to get:
Again, I may stop here as it is the look I want in my conversions. However, I tried one more cycle.
5. Run retinex once in a new layer, overlay with 25% opacity this time as 50% was too much.
THE FINAL IMAGE
Please note that I have not touched levels, curves, sharpening etc to show the usefulness of this very powerful filter.
I hope you enjoy. Please try it if you fancy and let me know about the experience.