Solarize Effect
Solarize a photo or video like a darkroom print flashed with light: tones past a pivot flip over, as in Man Ray's solarizations. Free, and nothing is uploaded.
What is solarization?
In the darkroom, solarization usually refers to the Sabattier effect. A print or negative gets partly developed, flashed briefly with white light, and then developed the rest of the way. Its tones partly reverse, so the picture ends up part positive and part negative. Thin lines called Mackie lines often form along the borders between dark and light areas.
Armand Sabattier described the effect in 1862, though others had noticed it a few years before. Man Ray took it up in Paris with Lee Miller, who got there in 1929, and his name for it, solarization, stuck.
Is solarization the same as the Sabattier effect?
Strictly speaking, no. True solarization happens in the camera. An exposure 1,000 to 10,000 times what it takes to turn film fully black makes it develop lighter instead of darker. It was first seen on daguerreotypes, and it's rare with modern film.
The Sabattier effect needs that second exposure. The flash forms latent image specks inside the grains of the midtones, not on their surface, which leaves those areas slow to develop. Parts that got little light the first time fog in proportion to the flash, and parts that already developed stay dark.
How does the solarize effect work?
It works on each pixel's brightness, the V of HSV. That's the strongest of its three channels, so a deep pure blue counts as fully bright. Curve, from 0.5 to 4, first raises the brightness to a power. Then the result gets folded at Pivot, from 0.1 to 0.9: tones below the pivot flip, so shadows turn light, and tones above climb again from black.
Since Curve comes first, the tone that turns black is the Pivot raised to 1 over Curve. At the defaults of 0.5 and 2, that's about 71 percent of full brightness. The presets are Darkroom for the defaults, Strong with Curve at 3.5, Low pivot at 0.25, and Tinted.
Colorize, from 0 to 1, sets each pixel's saturation from its original color times its original brightness, so whatever color survives sits in the parts that were bright. At the default 0.1 the result is close to monochrome, like a darkroom print. Tinted raises it to 0.6.
Settings for a Man Ray portrait, a psychedelic poster, a low-key print and a toned print
For a Man Ray portrait, use Pivot 0.5, Curve 2, Colorize 0 on a face lit from one side against a plain background. The fold draws dark contours where light turns to shadow. For a psychedelic poster, try Pivot 0.3, Curve 1, Colorize 0.8. Everything above 60 percent brightness climbs to full and keeps a strong hue.
For a low-key print, set Pivot 0.8 and Curve 1.5. With the pivot that high, the tones above it can only climb to a quarter of full brightness, so the highlights stay dim while the shadows flip to light. For a toned print, save a Darkroom result and give it a deep brown and a cream in Duotone Generator, like a solarized print that got toned later.
Invert Colors is the full reversal. There's no pivot, and no positive part is left.
Why did my solarized photo turn almost white?
Two parts of the curve go light: the shadows, which flip, and the tones well above the Pivot. Pure black always turns white here, because it sits at the far end of the flipped half. A photo with big black areas gets big white ones.
A low Pivot makes the climb above it steep. At 0.25, every tone past 0.5 after Curve is pure white. Raise Pivot to 0.5 or more, where the highlights can't clip, and keep the picture's darkest areas small.
Saving a solarized picture
The fold makes the tone curve steep. Below the Pivot, each step of brightness in the source becomes a step twice as big at the default, and Curve steepens parts of it even more. So JPG blocks and banding in the original turn into visible patches. Start from the best file you've got and save the result as PNG.