Adjusting inside a mask
Every mask on the frame has a row in the Masks section (⌃5), under the five rows that start one. Select a mask and the sliders under the list are its own. This page is what happens after a mask is placed; Local: masks is how to place one.
The masks on this frame
Under the five rows, every mask already on the frame has a row: its kind, a second line saying where it came from (Painted by hand, Detected on device · Vision, Graduated from the end you pressed), an On/Off switch and an × to remove it. A mask you have placed but not adjusted says no sliders moved until one does; a brush says how many strokes it holds; a mask with a range says ranged, an inverted one inverted.
Click a row to select it. Selecting changes nothing on the photograph; placing, adjusting, removing and switching are each their own ⌘Z. Masks compose in the order they are listed, and where two reach fully the later one wins. Turning one Off keeps it and everything about it and renders nothing, so what does this look like without that gradient costs one click and no lost work.
The section's own reset arrow removes every mask on the frame; to clear one, use the × on its row.
The eight sliders
With a mask selected, the eight sliders under the list belong to it: Exposure (−2 to +2 stops), Contrast, Highlights, Shadows, Temperature, Tint, Saturation and Vibrance (−100 to +100 each), on top of whatever the global sliders say. There is no ninth; these are the same eight the panel has above. Each shows a small put-back arrow once it has moved, which zeroes that one slider for this mask.
Narrowing a mask by tone or colour
Above the sliders sits range, with three chips: Off, Luminance and Hue. Off is the whole mask. Luminance narrows it to a band of tones — Low and High from 0 to 1, with a Softness — and starts on the upper half of the scale, the highlights. Hue narrows it to a band of colours — a Hue centre and a Width in degrees, with a Softness — and holds near-neutrals out. The line under the chips says what the range does in words: Only the colours within 30° of 0°, softened by 15° — near-neutrals are held out. A range applies to any kind of mask, a Subject or a Brush included.
Where a mask lives
A mask's shape is a fraction of the frame as delivered — after crop, straighten, rotate and flip — which is exactly the frame on the canvas. So a gradient does not follow the content through a later crop: crop after placing one and it stays where it is as a fraction of the new frame. A Subject mask is the exception and finds the subject wherever the crop puts it.
The subject as a scope
The Subject mask button on the top panel does something different from the Subject row. It scopes the frame's own global sliders — Exposure through Vibrance, on the Tone and Colour tabs — to the detected subject, without adding a mask. While it is on, the scope card at the top of the panel reads Subject only in violet, the canvas shows a tinted preview of what the subject means, and the card's Global button takes it off; the slider values go back to applying everywhere, nothing lost. If no subject is found, the canvas says so in words.
On a RAW file, Exposure, Temperature and Tint ignore the subject scope. The RAW decoder applies those three to the whole frame whatever the scope says, as The RAW stage explains. Only Contrast, Highlights, Shadows, Saturation and Vibrance stay inside the subject. On any other file all eight are scoped.
To change the exposure or the white balance of the subject alone on a RAW file, add a Subject mask from the Local tab instead and use that mask's own Exposure, Temperature and Tint, which work inside the mask.
While a mask is selected
Select a mask in the list and the scope card turns violet whichever tab you are on, names the mask (Linear mask, for one) and reads editing inside it · its own axes are in Local.
Only the eight sliders under the mask list write into the mask. The Exposure through Vibrance sliders on the Tone and Colour tabs go on moving the whole frame while a mask is selected, though the card is violet and says editing inside it. Press Global on the card to deselect the mask before you work on those tabs, and the card goes back to showing the look.