What you should know
A digital image is a grid of pixels, each carrying a colour. The format decides how that grid is described: lossless for PNG, lossy and very efficient for JPEG, vector-based for SVG, modern and compact for WebP and AVIF.
The format is therefore chosen according to the nature of the image — photograph or graphic — and according to the destination: web publishing, printing, exchange, retouching.
Strengths
- Formats suited to each use, from photo to logo
- Quality can be tuned finely to find the right weight
- Metadata preserves shooting conditions
- Transparency is available in graphic formats
Limitations to know
- JPEG degrades with every save
- PNG is heavy for photographs
- WebP and AVIF are not yet universally accepted offline
- SVG does not suit pixel images
When to use it
Shoot and retouch in PNG or RAW, publish in WebP or AVIF, exchange in JPEG, and reserve SVG for logos and icons. For printing, stay with JPEG or TIFF depending on the printer's requirements.
Quality, size and compatibility
The golden rule: never re-encode a lossy image from an already compressed file. Start from the original whenever possible. For the web, a quality of 80–85% offers the best weight-to-rendering ratio.
Frequently asked questions
- Which format for a logo?
- SVG if the logo is geometric: it stays sharp at every size. Otherwise, a PNG with transparency. JPEG should be avoided; it creates halos around edges.
- Why are my images heavier after conversion?
- Either the output quality exceeds the source, or the chosen format is less efficient for that kind of image. Check the setting and the format: PNG for flat areas, JPEG or WebP for photos.