LESSON 08 · DIGITAL FOUNDATIONS

A selection is a temporary fence that stops paint going where you do not want it. A mask is that fence saved onto a layer so you can change your mind about it forever. Together they are how you stop erasing things you might want back, which is the habit that separates a file you can rescue from one you cannot.

SOFTWARE

Finish first: L7

• Your layered file from Lesson 7, or the layer stack template
• Photoshop open with the Layers panel visible
• ArtRage 6 open with any painting on the canvas

WATCH

PHLEARN — Direct modern equivalent of 'What is a Mask?' (2011). Same concept, current UI, clean education channel.

PHLEARN — Selections and edge refinement on the 2026 toolset - the selection half of the Adobe Live video, three years newer.

Ambient Design — The same idea in ArtRage, from the people who wrote it — worth watching before you touch the Stencils tool.

THE LESSON

When you make a selection, an area of the canvas is marked off with a moving dashed outline — marching ants. Until you cancel it, everything you do only happens inside the fence. Paint across the boundary and the paint stops dead at the line. Delete, fill, blur, adjust: all of it is confined.

This is the digital version of masking tape — an edge that guarantees a clean boundary you could not draw freehand, except that this one can be any shape, soft or hard, and can be inverted to protect the inside instead of the outside.

Selections are temporary by design. Ctrl+D on Windows or Cmd+D on macOS deselects, and this is the most important shortcut in the section: if a program suddenly refuses to let you paint anywhere, the usual cause is a selection you forgot about, hiding somewhere off the visible canvas. Deselect first, then panic.

Photoshop gives you three families of selection tool. The marquee tools (M) drag out rectangles and ellipses, for panel borders, windows and anything geometric. The lasso tools (L) draw a freehand boundary, which with a pen in your hand is genuinely fast. The automatic tools (W) — Object Selection, Quick Selection and Magic Wand — guess the boundary from colour and contrast, which works brilliantly on flat colour and poorly on soft edges.

Combine them rather than trying to get one perfect. Hold Shift to add to an existing selection, Alt or Option to subtract. Most real selections take four or five passes: rough it in with the automatic tool, then add and subtract with the lasso.

Two commands do the rest. Select > Inverse (Shift+Ctrl+I or Shift+Cmd+I) flips the fence, which is how you select a background — select the object, then invert. Select > Modify > Feather (Shift+F6) softens the edge by a set number of pixels, so the boundary fades instead of cutting. A hard-edged selection on a soft-edged subject is what makes digital work look pasted together, so a two- or three-pixel feather is often the difference between a cut-out and a painted edge.

Everything above disappears the moment you deselect. A layer mask makes it permanent and editable. Select a layer and click the mask button at the bottom of the Layers panel, or use Layer > Layer Mask > Reveal All, and a second white thumbnail appears beside your layer's. That thumbnail is the mask.

The rule is three words: black conceals, white reveals. The mask is a greyscale image the same size as your layer. Wherever it is white, the layer shows normally. Wherever it is black, the layer is hidden — not erased, hidden. Wherever it is grey, the layer shows partially, so a soft grey gradient in a mask gives you a fade.

Which means: click the mask thumbnail to target it, then paint on it with an ordinary brush. Paint black to hide parts of your layer, paint white to bring them straight back. This is why professionals rarely use the eraser: an eraser destroys pixels and your only route back is undo, which stops working once you close the file, while a mask hides pixels and hidden is reversible forever. Invert a mask with Ctrl+I or Cmd+I, and switch it off temporarily by Shift-clicking its thumbnail.

Masks and clipping (Lesson 7) stack happily together. Clipping constrains a layer to the shape of the layer below; a mask constrains it to a shape you painted yourself.

Masks are one case of a bigger principle worth adopting now: prefer the version of an action you can undo tomorrow. Every choice in a drawing is a guess about what will look right at the end, and you will be wrong about some of them. Work that keeps its options open lets you fix the wrong guesses.

Adjustment layers are the other big example. Layer > New Adjustment Layer gives you Levels, Curves, Hue/Saturation and the rest as a layer floating above your artwork, changing how everything below it looks without altering a single pixel. Dial it, hide it, delete it, or paint on its built-in mask so the adjustment only affects part of the picture. Apply the same change directly to a painted layer and the old values are gone the moment you save and close.

Being destructive is not forbidden — sometimes flattening a section is the fastest way forward. The rule is to know which you are doing: save a version first (Lesson 5), then go ahead without worrying.

ArtRage has a Selections tool among its digital utility tools, and it works the way you would expect: mark an area, and paint stays inside it.

Its more distinctive tool is Stencils, which has three modes and is worth learning properly. In Stencil mode the shape is red and blocks paint, like a physical mask. In Ruler mode it is grey and guides the cursor, like a ruler your stroke slides along. In Guide mode it is blue, guides the stroke, but lets paint through. All three can be moved, rotated and scaled, and none ever appear in an exported image.

If you have used a real stencil or a French curve on paper, you already understand this tool better than most people who start digitally. That is the theme of the whole module: you are not learning to draw again, you are learning where your tools have been moved to.

PRACTICE · 35 MIN

1. Open your Lesson 7 file. On the flats layer, use the lasso to select one part of the drawing, then Shift-lasso to add a second part and Alt-lasso to remove a bit you overshot.
2. With that selection active, paint a stroke that deliberately runs well past the edge, and confirm the paint stops at the fence. Then press Ctrl+D to deselect.
3. Select the same shape again, then use Select > Inverse and fill the result with a flat background colour. Deselect.
4. Add a layer mask to your shading layer. Paint black on the mask over half your shadows and watch them vanish, then paint white over the same area to bring them back.
5. Make a soft black-to-white gradient on a mask so one edge of a layer fades out gradually.
6. Redo the same hiding job on a duplicate layer using the eraser instead. Save, close, reopen, and try to bring back what you erased. Note in one sentence what you just proved.
7. Add an adjustment layer above the whole stack — Levels or Hue/Saturation — and push it far enough to look obviously wrong. Then hide it, and note that nothing underneath changed.
8. In ArtRage, load or draw a shape with the Stencils tool and paint across it in Stencil mode, then switch it to Guide mode and paint across it again. Describe the difference in your own words.
9. Save the layered file as a new version.

Done when: You have one layer whose visible shape is controlled entirely by a mask you can paint back at any time, one adjustment layer you can toggle, and a written sentence explaining the difference between erasing and masking after a file has been closed and reopened.

Download these and work along with the lesson.

CHECK YOURSELF

Answer out loud first, then open each one to compare.