How to Use Quick Mask in Photoshop (Q)

Pressing Q toggles Quick Mask mode in Photoshop. The selection you have becomes a red overlay you can paint on with any brush, and pressing Q again turns the painted result back into a selection. **This is the answer to selections that are almost right.** A magic wand or a subject selection gets close and then misses a strand of hair or grabs a bit of background. Refining that with the selection tools means holding Shift and Alt while retracing edges, which is fiddly. In Quick Mask, the same correction is painting — black adds to the masked area, white removes from it, and a soft brush produces a soft edge that would be tedious to construct any other way. **The colours are inverted from what people expect, and this is the first stumbling block.** Painting with black *adds* to the mask, which *removes* from the selection. Painting with white does the reverse. The red overlay shows what is masked, meaning not selected. If your corrections are doing the opposite of what you want, press X to swap the foreground and background colours rather than trying to reason it out — the swap is instant and the feedback is immediate. **Grey is the feature that has no equivalent elsewhere.** Ordinary selections are binary — a pixel is in or out. A mask painted in grey produces a partial selection, so a 50% grey area is half selected and any adjustment applies at half strength. That is how you build a gradual falloff into an adjustment: paint a gradient in Quick Mask, exit, and the resulting selection fades rather than stopping at an edge. Nothing in the marquee or lasso tools can express that. **Quick Mask is temporary by design.** Exiting converts to a selection and the mask is gone; there is nothing saved. For something you want to keep, Select ▸ Save Selection stores it as an alpha channel, or applying it as a layer mask keeps it editable indefinitely. The rule of thumb is that Quick Mask is for refining a selection you are about to use, and a layer mask is for a decision you may revisit. **Double-clicking the Quick Mask button in the toolbar opens its options**, where you can invert what the overlay represents and change its colour and opacity. The colour matters more than it sounds: the default red is invisible on a red subject, and switching to green or blue for that image is the difference between seeing your mask and guessing at it. **Q is shared with SketchUp's Rotate tool and Krita's Multibrush**, which is worth a moment's thought for anyone moving between applications. In Photoshop the letter is unmodified and toggles a mode rather than selecting a tool, so it is safe to press to find out where you are — pressing it twice returns you to exactly where you started. **Quick Mask pairs naturally with a selection made by another route.** Select Subject or Object Selection gets you eighty percent of the way in one click; Q and a brush handle the remaining twenty. That division of labour — automated selection for the bulk, painting for the edges — is faster than either approach alone and is how most retouching work actually proceeds.