Digital Graphic Tools
The digital domain is examined through decisions, not software menus: raster or vector, resolution for a final size, colour mode for an output, and a file format that preserves what the next step needs.
Raster versus vector
- Raster: a pixel grid; enlarging interpolates and softens edges. Native to photography, painting apps, textured work.
- Vector: mathematical paths and fills; resolution-independent. Native to logos, typography, diagrams; formats SVG, AI, PDF.
- Choose vector when the artwork must scale (signage, identity) and raster when it depicts continuous tone.
Resolution and colour
- Print needs about 300 ppi at final size; screen work 72-150 ppi. DPI describes printer dots, PPI describes image pixels; they are not interchangeable.
- RGB is additive, for screens; CMYK is subtractive, for ink. Conversion shrinks the gamut, so soft-proof with the printer's ICC profile before finalising.
- 8-bit versus 16-bit depth matters in smooth gradients: low bit depth produces banding.
Formats and production
- TIFF (lossless, print), PSD (layers, working master), PNG (lossless with transparency), JPEG (lossy, visible artifacts after re-saving), SVG (vector web), PDF/X (print-ready).
- Add bleed (commonly 3 mm) and crop marks; keep the layered master untouched and export copies.
Worked example
Size a 29.7 × 42 cm poster at 300 ppi with 3 mm bleed. Convert to inches, then multiply by 300: width 29.7/2.54 × 300 ≈ 3508 px; height 42/2.54 × 300 ≈ 4961 px. Add the bleed: (29.7 + 0.6) cm becomes about 3579 px, height about 5032 px. Reasoning: resolution is defined at final size, so both dimensions and bleed change the pixel count.
Marks-losing traps
- Designing at 72 ppi and upscaling at the end; interpolation cannot invent detail.
- Sending an RGB JPEG to a press instead of a CMYK or PDF/X file with the right profile.
- Flattening and overwriting the layered master.
- Confusing dpi and ppi in the written answer.
- Omitting bleed, so trimming cuts into the design.