Document Setup, Layers, and Selections
Document setup essentials
Understand the difference between Image Size (resamples or resizes the pixel grid) and Canvas Size (adds or removes canvas without scaling content, anchored by the grid). Know resolution's relationship to print: pixels per inch determines physical size at a given pixel count. Color mode (RGB, CMYK, Grayscale) and bit depth (8 vs 16) are set at creation and affect available adjustments. Resample options (Bicubic, Bicubic Sharper for downsampling, Bicubic Smoother for upsampling) are commonly tested.
Layers
Candidates must know layer types: raster, text, shape, adjustment, fill, and Smart Object. Understand stacking order, opacity vs fill, blend modes, layer groups, and linking. Adjustment layers are non-destructive and carry their own mask - a key exam distinction from Image > Adjustments, which is destructive.
Selections
Selections define an editable region. Know the marquee, lasso, magnetic lasso, quick selection, object selection, and Select Subject. Understand feathering (soft edges), anti-aliasing, Refine Edge/Select and Mask for hair and edges, and modify commands (contract, expand, feather, smooth). Quick Mask converts a selection into a paintable channel-like overlay.
Worked rule of thumb
If a stem asks how to keep an adjustment editable later, the answer is an adjustment layer, not Image > Adjustments. If it asks how to change physical print size without changing pixel dimensions, change resolution, not canvas.
Traps
Selecting All then transforming affects the whole layer, not the canvas. Tolerance and contiguous settings on magic wand and paint bucket change results dramatically.