Quote:

Originally Posted by **Doug Nelson** Obviously they don't cancel each other, as we both just demonstrated. But shouldn't they cancel out in theory? If +delta = -delta, shouldn't you end back up with the original value? So therefore any introduced difference is all on Photoshop? |

I suggest consulting a book on numerical analysis and/or fixed point math, because even in theory it doesn't always work that way. As John pointed out it uses

splines, which aren't exactly linear mappings. Even if we restricted this to operations that specifically use linear mappings,

they aren't always invertible. You lose some amount of additional stability due to numerical rounding, but that's just an additional detail. An example of a linear mapping would be a conversion between color spaces, but even these aren't completely isomorphic, as they often contain different boundary conditions that are resolved by some sort of clamping, typically performed at each stage of computation.

Quote:

Originally Posted by **Doug Nelson** John:
So the inverse curve point to 64,32 would not be 64,96 but rather 32,64?
Using this curve gives similarly changed results. |

It's impossible to know every step that occurs under the hood there, although I can make guesses. As I mentioned it doesn't have any symbolic utilities, as it's not mathematica. In theory