One of the more complex adjustments, gamma is extremely useful for a whole host of purposes. I’ll limit the scope of gamma in this article to purely grading purposes (and will probably write a more in-depth one on Gamma alone in the future). As you can see from the demo above, it is unique in that it can break the linearity of the image, darkening or brightening it without touching the black and white values. None of the above can do this — notice that without gamma the curve always retains its linearity. Gamma however is more practical for contrast adjustments as blackpoint/whitepoint adjustment is very harsh on the top and bottom end. This allows for smoother results, similar to plotting custom points on a curve in Photoshop or with a Colour Lookup.

Clamping

Remapping values using the Grade will very quickly plunge black values lower into the negative domain, as if you were to sample anything but the darkest pixel in the image then the darker value will be set less than 0. Nuke defaults to clamping the blacks after applying the image adjustments for this reason. You would need to untick this box if remapping noise or other maps used for displacement in the negative direction.

Demonstration