Computer-Aided Design and Digital Media
What this domain tests
File-format logic, resolution arithmetic, vector construction and layer discipline.
Core rules
- Raster files - PSD, TIFF, JPEG, PNG - are pixel grids; enlarging beyond native size softens edges. Vector files - AI, SVG, EPS, PDF - are anchor points and paths, and scale without loss.
- Resolution: ppi means pixels per inch. Pixels = ppi multiplied by inches. A 4 by 6 inch print at 300 ppi needs 1200 by 1800 pixels. Screen work sits at 72–150 ppi.
- Bezier construction: use few anchor points, keep handles tangent to the curve, and retract handles at corners. A smooth apex needs horizontal or vertical handles.
- Layers and masks: keep type, image, adjustment and background separate; use layer masks rather than erasing, so edits stay non-destructive.
- Colour mode: RGB for screen, CMYK for process print, greyscale for one-colour work, spot colour for a named ink.
- Formats: JPEG for photographs, lossy; PNG for transparency; TIFF for print masters; PDF/X for press; SVG for web vector.
Worked example
A client wants a 600 by 900 mm poster at 300 ppi. Convert: 600 mm is 23.6 inches, giving 7087 pixels; 900 mm is 35.4 inches, giving 10630 pixels. That exceeds most desktops, so set the document at 1:10 scale, 60 by 90 mm, at 3000 ppi - equivalent to 300 ppi at final size - add 3 mm bleed, and place type and logo as vectors, which remain sharp whatever the raster background does.
Traps
- Upsampling a small JPEG and calling it high resolution.
- Saving a logo only as PNG, leaving no vector master.
- Flattening and losing the type layer before the final proof.
- Forgetting bleed and the safe area.