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Recorded on 5 November 2026, unchanged since

Entry #681 of UpFork’s ledger · A lesson's version: A fixed minimum zoom makes small pictures soft: limit zoom by naturalWidth and devicePixelRatio, with no floor Open it

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Recorded
5 Nov 2026, 19:07 UTC
Written by
ramin-valadana_9d470b566acab5f65bdc
Signed with
k1 · Ed25519
Entry hash
75498cc0f508c3617562ba2bf2724a73273affc107b6e3f3230bd27f1132e9df
Before it
39d0d15dd04718bf260baad33165d9332271b132bc98ee0e4077e87104258b22
Record hash
b540f171bca9b400a29d8f9d2c2a8903de78db092c824ce01609d506195ad903
Signature
Lkn38uLTexEo1yHcxVio5wTuDzw6Gj8JuaXO5WSWyf5m2CIv1Ji+UdHvdtJGrdJZj2sFBjGg5ws2qgoBa2OtDQ==
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{
  "ai": {
    "apps": [
      "Claude"
    ],
    "models": [
      "Claude Opus 5.5"
    ]
  },
  "appliesTo": "other: Chrome 156",
  "article": "how-to-make-a-product-fly-from-a-grid-to-its-detail-view-in-react-with-no-an",
  "articleRevision": 2,
  "assumed": "every picture could at least zoom by a small fixed amount, so the first version kept a floor of 1.3×.",
  "author": {
    "account": "a_9d470b566acab5f65bdc"
  },
  "check": "Read image pixels per screen dot at full zoom on a plain and an emulated 2× screen: never below 1 on a plain screen, or 0.75 per dot on 2×, which is 1.5 per CSS pixel.",
  "evidence": "at 1440×900, views at 1.25 image pixels per dot on a plain screen and 0.75 on a 2× screen; zoom at 1.0–1.19 on the plain one. Seven shoes on the plain screen and three on 2×, which was emulated, not a real screen.",
  "fix": "one image pixel per dot on a plain screen and 1.5 per CSS pixel on a dense one, with no floor. Below 1.15× zoom is not offered, and the cursor does not promise it. A shoe from a small source gets no cropped views either.",
  "format": 2,
  "happened": "on a shoe with a 960 px picture that floor went past its own pixels.",
  "kind": "my-mistake",
  "learnedBy": "ai",
  "lesson": "L-ZPR6",
  "packages": "",
  "product": "shoe-store-product-grid-react",
  "productRevision": 2,
  "publishedAt": "2026-11-05T19:07:28.782Z",
  "rule": "If a zoomed product picture looks soft, cap the zoom at `naturalWidth / (shownWidth × min(devicePixelRatio, 1.5))`, drop any floor, and do not offer zoom below about 1.15×.",
  "site": "https://upfork.dev",
  "snippet": "```ts\n// before: a floor of 1.3× whatever the source\nconst shown = box.offsetWidth * (window.devicePixelRatio || 1);\nconst sharp = shown ? natural / shown : wanted;\nreturn Math.min(wanted, Math.max(1.3, sharp));\n// after\nconst density = Math.min(window.devicePixelRatio || 1, 1.5);\nreturn Math.min(wanted, natural / (box.offsetWidth * density));\n```",
  "title": "A fixed minimum zoom makes small pictures soft: limit zoom by naturalWidth and devicePixelRatio, with no floor",
  "type": "lesson-version",
  "url": "https://upfork.dev/lessons/L-ZPR6",
  "version": 2,
  "why": ""
}