{
 "version": "2026-10-20",
 "license": "Dimension sheets: CC BY 4.0. Standard and published-size files: CC BY 4.0. Xem Studio's own designs (files_license = Xem Studio Design License): free to use and sell things from, not to redistribute as files — https://xemstudio.com/license/. Other publishers' files: their own license, linked beside them.",
 "slug": "canon-rf-mount",
 "name": "Canon RF mount: 20 mm flange focal distance, 54 mm diameter",
 "kind": "standard",
 "category": "Cameras & lenses",
 "group": "Lens mounts & filter threads",
 "year": null,
 "question": "What is the Canon RF flange focal distance and throat diameter?",
 "tags": [
  "lens mount",
  "camera",
  "lens",
  "mount",
  "adapter",
  "flange distance",
  "standard"
 ],
 "aliases": [
  "canon rf flange distance",
  "rf mount diameter",
  "canon rf mount dimensions",
  "rf mount 54mm",
  "ef to rf adapter thickness"
 ],
 "overall_mm": {
  "length": null,
  "width": null,
  "height": null
 },
 "official_cad": false,
 "xem_status": "not-scanned",
 "les": false,
 "free_files": 0,
 "url": "https://xemstudio.com/objects/canon-rf-mount/",
 "sheet_txt": "https://xemstudio.com/objects/canon-rf-mount/sheet.txt",
 "sheet": {
  "basis": "Published numbers only (sources per row); no bayonet geometry is published, so no file",
  "overall_mm": {
   "length": null,
   "width": null,
   "height": null
  },
  "notes": [
   "Flange focal distance is the distance from the mount's reference face to the image plane; adapters and extension tubes must add exactly the difference between two mounts' flange distances to keep infinity focus.",
   "RF replaced EF on Canon's mirrorless bodies: the 54 mm diameter stayed, and the flange distance went from 44 mm to 20 mm, which is why an EF-to-RF adapter is 24 mm thick.",
   "No file: the bayonet's lug widths, angles, depths and locking geometry are not published by the maker, so nothing is drawn. Only the published numbers are given."
  ],
  "table": {
   "columns": [
    "parameter",
    "value",
    "from"
   ],
   "rows": [
    [
     "flange focal distance",
     "20 mm",
     "Canon (lens mount guide)"
    ],
    [
     "throat / inner diameter",
     "54 mm (mount diameter)",
     "Canon U.S.A. press release, 2018"
    ],
    [
     "coupling",
     "bayonet",
     "—"
    ]
   ]
  }
 },
 "sheet_text": "Canon RF mount: 20 mm flange focal distance, 54 mm diameter — dimension sheet\nSource: Xem Studio, https://xemstudio.com/objects/canon-rf-mount/  (sheet CC BY 4.0)\nBasis: Published numbers only (sources per row); no bayonet geometry is published, so no file\nCatalog version: 2026-10-20\n\nSizes: see table below\n- Flange focal distance is the distance from the mount's reference face to the image plane; adapters and extension tubes must add exactly the difference between two mounts' flange distances to keep infinity focus.\n- RF replaced EF on Canon's mirrorless bodies: the 54 mm diameter stayed, and the flange distance went from 44 mm to 20 mm, which is why an EF-to-RF adapter is 24 mm thick.\n- No file: the bayonet's lug widths, angles, depths and locking geometry are not published by the maker, so nothing is drawn. Only the published numbers are given.\n\nparameter  value  from\nflange focal distance  20 mm  Canon (lens mount guide)\nthroat / inner diameter  54 mm (mount diameter)  Canon U.S.A. press release, 2018\ncoupling  bayonet  —\n\nFiles elsewhere (not hosted by Xem Studio; license as stated by the publisher):\n- Canon: Camera lens mount guide (RF: 20 mm flange distance) — web — Publisher's page; dimensions are facts — https://en.canon-me.com/get-inspired/tips-and-techniques/choosing-right-lens-mount/\n- Canon U.S.A.: Canon introduces four RF mount lenses (press release, 5 Sep 2018): RF mount 54 mm diameter — web — Publisher's page; dimensions are facts — https://www.usa.canon.com/newsroom/2018/20180905-rf\n- Wikipedia: Flange focal distance (table of mounts) — web — CC BY-SA 4.0 (text); dimensions are facts — https://en.wikipedia.org/wiki/Flange_focal_distance\n\nNo true-size file yet: the published figures do not fix the whole shape; a measured scan is planned.\nAPI: https://xemstudio.com/api/geometry?object=canon-rf-mount\n",
 "sources": [
  {
   "publisher": "Canon",
   "title": "Camera lens mount guide (RF: 20 mm flange distance)",
   "url": "https://en.canon-me.com/get-inspired/tips-and-techniques/choosing-right-lens-mount/",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Canon U.S.A.",
   "title": "Canon introduces four RF mount lenses (press release, 5 Sep 2018): RF mount 54 mm diameter",
   "url": "https://www.usa.canon.com/newsroom/2018/20180905-rf",
   "formats": [
    "web"
   ],
   "license": "Publisher's page; dimensions are facts",
   "license_verified": true,
   "hosted": false
  },
  {
   "publisher": "Wikipedia",
   "title": "Flange focal distance (table of mounts)",
   "url": "https://en.wikipedia.org/wiki/Flange_focal_distance",
   "formats": [
    "web"
   ],
   "license": "CC BY-SA 4.0 (text); dimensions are facts",
   "license_verified": true,
   "hosted": false
  }
 ],
 "xem": {
  "status": "not-scanned",
  "sheet_free": true,
  "mesh_price_usd": null,
  "step_price_usd": null,
  "tolerance_mm": null
 },
 "related": [
  "canon-ef-mount",
  "sony-e-mount",
  "nikon-z-mount",
  "lens-filter-threads"
 ],
 "fits": [],
 "dimensions": "exact (nominal, no printing tolerance)",
 "dimension_rule": "All geometry on Xem Studio is exact (nominal, true size) with no printing tolerance. Where a part meets another part, the object lists its mating features (feature, exact size, what it mates with, fit class: press, slide, run, socket, clamp or designed). Apply your process's allowance to those features only; 'designed' gaps are part of the design and stay as drawn.",
 "mating": [],
 "faq": [
  {
   "q": "What is the Canon RF flange distance?",
   "a": "20 mm, with a 54 mm mount diameter (Canon)."
  },
  {
   "q": "Why is the EF-to-RF adapter 24 mm thick?",
   "a": "EF has a 44.00 mm flange distance and RF 20 mm: 44 − 20 = 24 mm."
  }
 ],
 "files_license": null,
 "offers": [],
 "markdown": "https://xemstudio.com/objects/canon-rf-mount/index.md"
}