I don't normally link to other sites but this one is very cool, even tho the image is apparently for a Sony camera ad(the brand in itself is not an issue, the ad itself is)
..anyhow, on Petapixel is this interesting way to invert colours...
Do as it says. Best way to see it easily and clearly is to use a browser with tab ability and have one blank tab opened.. white page only, not home page.
Stare at the coloured dots as explained keep your finger on the blank tab and after about 30sec of staring click the blank tab for a blank white screen and blink quickly.
As you instantly close your eyes, you see the positive, just as they say you will.
Also a new trick learned from this post(on PetaPixel) is that you can invert your screen's colours(Windows7) if you use the Magnifier tool. Cool
Came across this post as I was searching for alternative methods for processing negs into positive.