Digital Light & Color

With transformations that contain histogram control, there is a button that allows for showing the histogram for masked area only. I can't find a way of doing the same thing with the Histogram Tool - i.e. showing the histogram filtered through a mask.

That's because the histogram tool does not have a mask -- this would not be very practical as it switches as you change the current image.

I guess I borrowed the idea from PWP7, where the Histogram Tool allowed for applying any open mask as long as the pixel dimensions matched. I found it useful at times.

The paradigms are just different enough to make this difficult to implement in PWP 8. It would be a lot easier if Histogram was a transformation and not a tool, but that would probably be less useful since you could not leave it open.