FL_ReversibleSoftClip

It’s a softclip that can be reversed. It has no parameters, except for the Reverse toggle. It takes any values between zero and infinity and compresses them between zero and one. You can then bring the resulting image to Photoshop for example, paint on it, then bring it back in nuke and apply the reverse operation to recover the original values.

You can also use it to fake an HDR image from a normal jpeg photo. But be careful with values near 1 because they will end up near infinity.