When using a selective Global Adjustment tool (specifically, those tools like HSL, Selective Tone, and the FilmPack Contrasts) that operate only on selected pixels within the whole frame rather than on all pixels uniformly, allow a hotkey (like ‘M’ does for ControlPoints/Lines) to display a greyscale mask showing which pixels are being selected to what extent by the range that is currently set on the global tool.
For example, if using HSL then those pixels to be selected by the ‘live’ colour-range (as identified by the picker and/or by the active range/feather sliders) would be displayed in this greyscale mask when the ‘M’ key is pressed. The mask display would toggle off and on with the ‘M’ key. (There would also need to be a way to signal that it is the HSL tool is going to have its mask displayed when ‘M’ is pressed.) This would enable one to validate/tune the selection of the desired colour-range for HSL adjustment more precisely and to see whether areas of the frame were being affected unintentionally/unexpectedly by the adjustment.
At present, I can’t see a way within PL to approximate this masking effect for other global adjustments than HSL. It is possible to approximate a masking effect for HSL by sliding saturation to 0 on the selected colour-range, but even this does not really disclose the selection of pixels/areas that are not heavily selected because the display does not turn pure greyscale but instead is at best “muted colours with tinted greys”. And I don’t see a way within PL to do anything similar to reveal the selections of Contrast or Selective Tone tools. (The only option at present is to export the image and a VC to another photo-editor, one copy with and one copy without the selective tool settings, and blend the two versions in difference mode. That reveals the seleected pixels but is very cumbersome to iterate and requires one to use a competitor software extensively.)
NB. This feature is NOT requested as an alternative to moving all possible tools, like HSL, to be available as masked Local Adjustments. Nor is it requested that the masks be editable, just for accurate information of the user. (Sorry if this is nonetheless a direct duplicate of an existing feature request, but I could not see one when searching. Feel free to re-direct my post (and vote).)
Interesting request. As you noted: with HSL, reducing a color channel’s Saturation to 0 is a quick and easy way to give a masked view. Another - at least in Windows - is to hold the Ctrl key while clicking on the edges of the color range on the HSL wheel. (Click on the ? icon at the top of the HSL adjustment palette for instructions.)
What do you think about the possibility of using Ctrl while clicking on other global sliders to produce the mask view you are looking for? That seems like a relatively easy way to implement the mask view for a variety of tools. I would vote for that provided it can be useful for both color and grayscale photos. Otherwise, I’m happy with WYSIWYG.
Thanks @Egregius, I wasn’t aware of that shortcut with the HSL tool. It does achieve a masking effect in the reverse of my description - ie. it appears to reduce the channel-specific saturation of pixels in all unselected ranges, to render them in greyscale. It has the advantage over the ‘0 method’ I described of fewer clicks to operate.
Which of these two existing methods works better for the purpose of revealing the notional HSL mask seems to depend on whether one is trying to select a predominant colour within the frame or a subordinate colour - in the former case ‘0’ seems better and in the latter case ‘Ctrl-click’. But neither actually renders the result in an easily read mask of the kind I am requesting because both produce a mix of colour, muted-colour, and tinted grey. So I’d still like the feature. And of course not just for HSL.
I think the Ctrl-click UI you propose would be great as an implementation: hold Ctrl and click the global slider desired, to see a true grayscale mask of the pixels that will be affected if you then move the slider. Would assist with showing exactly where tools like HSL, Selective Tone, and FilmPack contrast are to be applied. Since the algorithms DxO uses for these selections are (entirely reasonably) proprietary, showing such a mask helps show what in the image may be affected besides the intended target.
With grayscale photos, this feature would be irrelevant for the HSL tool but not the other selective global adjustment tools. I don’t do much B&W photography but I can recall occasions where it would be useful to have such a mask for the Channel Mixer - basically showing precisely where each channel appears in the image, with just one Ctrl-click. (Other editors can easily show you this information and it would be preferable not to need to export from PL to access it.)