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Why repeatedly saving a JPEG strip can soften edges
Each lossy re-encode can discard detail that the next save cannot restore.
A photostrip may be exported, messaged, edited and saved again. Repeated JPEG compression can create blocks or ringing around faces and text, even when every file still opens normally.
Keep one source master
JPEG is a lossy format designed to reduce file size. When an edited JPEG is saved again, compression is applied to already compressed values. Keep a high-quality original and make new derivatives from it rather than repeatedly editing the latest compressed copy.
Evidence: Platform technical documentation
Compare the same crop
Place the original and received strip side by side at equal dimensions. Inspect hair, fine borders and small captions for block patterns or halos. A screenshot can add scaling and display effects, so compare actual image files rather than screenshots of their previews.
Choose a format for the next edit
Use a lossless working copy when transparency or repeated editing matters, then make one JPEG export at the required size and quality for sharing. Check the exported file after messaging because services may recompress it again.
Evidence: Web standard
Sources & further reading
Sources for the specific facts and product descriptions above. Our worked examples, interpretations and practical suggestions are original editorial guidance.
- Apple Developer, Capturing Uncompressed Image DataPlatform technical documentation
- W3C, Portable Network Graphics Specification, Third EditionWeb standard