Negative¶
These are all blending modes which seem to make the image go negative.
Additive Subtractive¶
Subtract the square root of the lower layer from the upper layer.

Left: Normal. Right: Additive Subtractive.¶
Arcus Tangent¶
Divides the lower layer by the top. Then divides this by Pi. Then uses that in an Arc tangent function, and multiplies it by two.

Left: Normal. Right: Arcus Tangent.¶
Difference¶
Checks per pixel of which layer the pixel-value is highest/lowest, and then subtracts the lower value from the higher-value.

Left: Normal. Right: Difference.¶
Equivalence¶
Subtracts the underlying layer from the upper-layer. Then inverts that. Seems to produce the same result as Difference.

Left: Normal. Right: Equivalence.¶