Shopify camera lens schema for AI shopping agents: isAccessoryOrSparePartFor, lens mount lock-in, and crop factor compatibility

Why mount strings in product titles fail AI agents

Camera lens product titles encode the lens mount in natural language: "Tamron 28-75mm f/2.8 Di III VXD G2 for Sony E-Mount" or "Sigma 35mm f/1.4 DG DN Art (Canon RF)". The mount is there — but it's embedded in a string that AI shopping agents must parse rather than read from a structured field.

This creates three failure modes:

• Mount name ambiguity. "Sony E-Mount", "Sony FE mount", "E-mount", "FE-mount", and "Sony α FE" all refer to the same physical mount. Without a canonical value in additionalProperty, an AI agent matching "Sony FE" against a listing that says "E-Mount" may treat them as different mounts and exclude the product from the results.
• Third-party product code pollution. Sigma's DG DN Art naming convention means "DG = full-frame image circle, DN = mirrorless design, Art = optical quality line" — none of which an AI agent knows without a specification table. "Sigma 35mm f/1.4 DG DN Art for L-Mount" buries the critical mount identifier after product-line codes that are meaningless to a shopping agent parsing a title string.
• APS-C vs full-frame ambiguity within the same mount. The Sony E-mount accepts both APS-C format lenses (designed for A6xxx APS-C bodies) and full-frame FE lenses (designed for A7/A9 full-frame bodies). "E-Mount" in the title doesn't tell an AI agent whether the lens covers the full-frame sensor or only the APS-C crop. Buying an APS-C E-mount lens for a full-frame A7 IV causes severe vignetting — the image circle is too small for the sensor.

The fix requires two machine-readable signals: additionalProperty.lensMount with a canonical mount name, and additionalProperty.imageCoverage with the sensor format the lens covers. Together they give AI agents the filter they need to match lenses to bodies without parsing title strings.

The 8 lens mount reference table

Use these canonical mount names in your additionalProperty — not brand-specific abbreviations like "RF", "Z", or "FE" without the manufacturer prefix, which are ambiguous across ecosystems.

In additionalProperty, use the canonical mount name from the first column exactly. For image circle coverage, use a separate PropertyValue entry with "Full-Frame", "APS-C", or "Micro Four Thirds" as the value — do not combine mount and format into a single string.

Crop factor and image circle: the compatibility math

The reason format matters more than mount is image circle coverage. Every lens projects a circular image onto the sensor. The sensor sits in the center of that circle. If the sensor is smaller than the image circle, everything works. If the sensor is larger than the image circle, the corners go dark — vignetting.

The sensor diagonal is the critical number. A full-frame sensor has a 43.3mm diagonal. An APS-C lens projects a 28.4mm circle. 28.4mm < 43.3mm — the circle cannot cover the corners of the FF sensor. This is why an APS-C E-mount lens on a Sony A7 IV creates visible vignetting in all four corners.

The 3 APS-C vs full-frame mounting scenarios

There are three distinct scenarios when APS-C and full-frame formats interact. Each needs a different encoding in your structured data:

The second scenario — APS-C lens on full-frame body — is the one that generates the most returns. It's also the scenario most commonly enabled by AI agents recommending lenses based on mount name alone without format scope. The isAccessoryOrSparePartFor ProductGroup for an APS-C lens must reference an APS-C-scoped group ("Sony APS-C Mirrorless Cameras"), not the full E-Mount ecosystem that includes full-frame A7 bodies.

Third-party lenses and the compatibleWith pattern

Third-party lens manufacturers — Sigma, Tamron, Tokina, Viltrox, Laowa, Venus Optics — produce lenses in multiple mounts for the same optical formula. A Sigma 35mm f/1.4 Art ships in Canon RF, Nikon Z, Sony E-Mount, L-Mount, and previously Canon EF and Nikon F variants. Each variant is a separate product that needs its own isAccessoryOrSparePartFor and compatibleWith entries.

The compatibleWith property lists specific camera bodies where compatibility has been verified. For a third-party Sony FE lens, this typically includes the major A7/A9 bodies:

"compatibleWith": [
  {
    "@type": "Product",
    "name": "Sony Alpha 7 IV (ILCE-7M4)",
    "brand": { "@type": "Brand", "name": "Sony" }
  },
  {
    "@type": "Product",
    "name": "Sony Alpha 7R V (ILCE-7RM5)",
    "brand": { "@type": "Brand", "name": "Sony" }
  },
  {
    "@type": "Product",
    "name": "Sony Alpha 9 III (ILCE-9M3)",
    "brand": { "@type": "Brand", "name": "Sony" }
  },
  {
    "@type": "Product",
    "name": "Sony Alpha 1 II (ILCE-1M2)",
    "brand": { "@type": "Brand", "name": "Sony" }
  },
  {
    "@type": "Product",
    "name": "Sony ZV-E1 (Full-Frame Vlog Camera)",
    "brand": { "@type": "Brand", "name": "Sony" }
  }
]

For Sigma's cross-mount naming conventions, include the Sigma product line code as an additionalProperty so buyers searching by Sigma's own nomenclature can still find the lens via structured data:

{
  "@type": "PropertyValue",
  "name": "Sigma Product Line Code",
  "value": "DG DN Art",
  "description": "DG = full-frame image circle; DN = mirrorless-native optical design (optimized for short flange distance); Art = Sigma Contemporary Art line (maximum optical performance priority)"
}

The description field explanation of the Sigma code is not redundant — it gives AI agents the context to correctly associate "Sigma Art" with "maximum optical quality" in buyer-facing responses, and to understand "DG" as a full-frame signal when image circle coverage isn't stated separately.

Adapter compatibility: Canon EF on RF bodies

If you sell legacy Canon EF or Nikon F lenses alongside the bodies that use the Canon EF-EOS R adapter or Nikon FTZ II adapter, encode adapter compatibility explicitly. The buyer pool for EF lenses is substantially expanded by RF body owners who use the adapter:

{
  "@type": "PropertyValue",
  "name": "RF Mount Adapter Compatible",
  "value": "Yes — Canon Mount Adapter EF-EOS R (sold separately)",
  "description": "All EF lens functions retained on Canon RF bodies including autofocus, image stabilization, and aperture control. Compatible adapters: Canon Mount Adapter EF-EOS R (standard), Canon Control Ring Mount Adapter EF-EOS R (adds control ring), Canon Drop-In Filter Mount Adapter EF-EOS R (adds ND/CPL filter slot)."
}

For Nikon F lenses, include the AF motor caveat that generates the most buyer confusion:

{
  "@type": "PropertyValue",
  "name": "Nikon Z Mount Adapter Compatible",
  "value": "Yes — Nikon FTZ II Mount Adapter (sold separately)",
  "description": "Autofocus available ONLY for lenses with built-in AF motor (AF-S, AF-I designation). Older AF lenses with screwdriver-drive coupling do NOT autofocus on Z bodies — Nikon Z mount has no AF coupling screw. AF-P lenses: autofocus supported. All lenses retain aperture control and exposure metering."
}

isAccessoryOrSparePartFor: linking lens to camera mount

The schema.org/isAccessoryOrSparePartFor property creates the machine-readable "this product is an accessory for" relationship. For camera lenses, it links the lens to the camera mount ecosystem it belongs to — allowing AI shopping agents to filter lens results by the buyer's camera body without having to parse mount names from title strings.

The target of isAccessoryOrSparePartFor should be a ProductGroup representing the mount ecosystem, not an individual camera body. This is because a lens is an accessory for the entire Canon RF ecosystem, not just the R5 Mark II:

"isAccessoryOrSparePartFor": {
  "@type": "ProductGroup",
  "name": "Canon RF Full-Frame Mirrorless Cameras",
  "description": "Canon EOS R3, R5 Mark II, R5, R6 Mark II, R6, R8, R50 (full-frame RF bodies). Also compatible with Canon APS-C RF-S bodies (EOS R7, R10, R50) with 1.6× crop factor.",
  "url": "https://www.bhphotovideo.com/c/browse/canon-rf-cameras/ci/22959"
}

The description field within the ProductGroup is the right place to document crop factor behavior on APS-C RF bodies — this is a note about the relationship between the lens and a subset of bodies in the ecosystem, not a property of the lens itself.

For APS-C format lenses where the ProductGroup scope must be restricted to APS-C bodies only, scope the ProductGroup name and description explicitly:

"isAccessoryOrSparePartFor": {
  "@type": "ProductGroup",
  "name": "Sony APS-C Mirrorless Cameras (E-Mount, APS-C sensor)",
  "description": "Sony Alpha A6700, A6600, A6400, A6100, ZV-E10 II — APS-C bodies only. NOT compatible without vignetting on Sony full-frame bodies (A7, A9, A1 series) unless APS-C crop mode is manually enabled.",
  "url": "https://www.sony.com/en/products/cameras/aps-c/"
}

The "NOT compatible without vignetting" language in the ProductGroup description is the machine-readable incompatibility signal. AI shopping agents parse this to correctly exclude the lens from results when the buyer specifies a full-frame body.

Complete JSON-LD example: Sony FE zoom lens

A complete Product structured data block for a Tamron 28-75mm f/2.8 Di III VXD G2 in Sony FE mount, as it would appear in a <script type="application/ld+json"> tag in the product page <head>:

{
  "@context": "https://schema.org",
  "@type": "Product",
  "name": "Tamron 28-75mm f/2.8 Di III VXD G2 for Sony FE (Model A063)",
  "description": "Full-frame standard zoom lens for Sony E-Mount mirrorless cameras. 28-75mm range with constant f/2.8 aperture. Optimized for Sony A7 and A9 series full-frame bodies. Includes moisture-resistant construction and internal zoom design. Not an OEM Sony lens — third-party with Sony E-Mount protocol compatibility.",
  "brand": {
    "@type": "Brand",
    "name": "Tamron"
  },
  "sku": "A063S",
  "gtin13": "4960371006505",
  "isAccessoryOrSparePartFor": {
    "@type": "ProductGroup",
    "name": "Sony Full-Frame Mirrorless Cameras (E-Mount FE)",
    "description": "Sony Alpha 7 IV, 7R V, 7C II, 7S III, 9 III, 1 II, ZV-E1 — full-frame E-Mount bodies. Also usable on Sony APS-C E-Mount bodies (A6700, A6600) with 1.5× crop factor, effective focal length 42-112mm f/2.8."
  },
  "compatibleWith": [
    { "@type": "Product", "name": "Sony Alpha 7 IV (ILCE-7M4)", "brand": { "@type": "Brand", "name": "Sony" } },
    { "@type": "Product", "name": "Sony Alpha 7R V (ILCE-7RM5)", "brand": { "@type": "Brand", "name": "Sony" } },
    { "@type": "Product", "name": "Sony Alpha 7C II (ILCE-7CM2)", "brand": { "@type": "Brand", "name": "Sony" } },
    { "@type": "Product", "name": "Sony Alpha 9 III (ILCE-9M3)", "brand": { "@type": "Brand", "name": "Sony" } },
    { "@type": "Product", "name": "Sony Alpha 1 II (ILCE-1M2)", "brand": { "@type": "Brand", "name": "Sony" } }
  ],
  "additionalProperty": [
    {
      "@type": "PropertyValue",
      "name": "Lens Mount",
      "value": "Sony E-Mount"
    },
    {
      "@type": "PropertyValue",
      "name": "Image Circle Coverage",
      "value": "Full-Frame (43.3mm image circle — covers 36×24mm FF sensor with no vignetting)"
    },
    {
      "@type": "PropertyValue",
      "name": "Focal Length",
      "value": "28-75mm (zoom)",
      "description": "Standard to short telephoto range. On Sony APS-C bodies: effective 42-112mm (1.5× crop factor)."
    },
    {
      "@type": "PropertyValue",
      "name": "Maximum Aperture",
      "value": "f/2.8 (constant throughout zoom range)"
    },
    {
      "@type": "PropertyValue",
      "name": "Optical Stabilization",
      "value": "No optical stabilization (OS)",
      "description": "Relies on in-body image stabilization (IBIS) from compatible Sony bodies. Sony A7 IV: 5.5-stop IBIS. Sony A7R V: 8-stop IBIS with lens coordination."
    },
    {
      "@type": "PropertyValue",
      "name": "Autofocus Motor",
      "value": "VXD linear motor (Voice coil eXtreme-torque Drive)",
      "description": "Tamron's VXD AF motor: high-speed, silent autofocus compatible with Sony's Fast Hybrid AF (phase-detect + contrast-detect). Full eye-tracking and animal-tracking AF compatibility on A7 IV and A9 III."
    },
    {
      "@type": "PropertyValue",
      "name": "Filter Thread Diameter",
      "value": "67mm"
    },
    {
      "@type": "PropertyValue",
      "name": "Minimum Focus Distance",
      "value": "19cm (wide end) / 38cm (tele end)"
    },
    {
      "@type": "PropertyValue",
      "name": "Weather Sealing",
      "value": "Yes — moisture-resistant construction",
      "description": "Tamron moisture-resistant construction with sealing at critical joints. Not IP-rated — no independent certification number. Suitable for light rain; not submersion."
    },
    {
      "@type": "PropertyValue",
      "name": "Zoom Type",
      "value": "Internal zoom (barrel does not extend during zoom)"
    },
    {
      "@type": "PropertyValue",
      "name": "Tamron Product Line Code",
      "value": "Di III VXD G2",
      "description": "Di III = designed exclusively for mirrorless cameras (Di = Digitally Integrated design; III = mirrorless-only); VXD = VXD linear AF motor; G2 = second generation of this optical design."
    }
  ],
  "offers": {
    "@type": "Offer",
    "price": "699.00",
    "priceCurrency": "USD",
    "availability": "https://schema.org/InStock",
    "priceValidUntil": "2026-07-01",
    "hasMerchantReturnPolicy": {
      "@type": "MerchantReturnPolicy",
      "returnPolicyCategory": "https://schema.org/MerchantReturnFiniteReturnWindow",
      "merchantReturnDays": 30,
      "returnMethod": ["https://schema.org/ReturnByMail"],
      "returnFees": "https://schema.org/FreeReturn"
    }
  }
}

Dawn Liquid snippet for lens.* metafields

Add the following metafields to your camera lens products in Shopify Admin (Settings → Custom data → Products), then use this snippet in sections/main-product.liquid to output lens-specific structured data:

{% comment %} Camera lens structured data — place in main-product.liquid {% endcomment %}
{% assign is_camera_lens = false %}
{% if product.metafields.lens.mount != blank %}
  {% assign is_camera_lens = true %}
{% endif %}

{% if is_camera_lens %}
{% assign lens_mount = product.metafields.lens.mount | default: '' %}
{% assign lens_format = product.metafields.lens.format | default: '' %}
{% assign lens_focal = product.metafields.lens.focal_length | default: '' %}
{% assign lens_aperture = product.metafields.lens.max_aperture | default: '' %}
{% assign lens_filter = product.metafields.lens.filter_thread | default: '' %}
{% assign lens_mfd = product.metafields.lens.min_focus_distance | default: '' %}
{% assign lens_af = product.metafields.lens.af_motor | default: '' %}
{% assign lens_os = product.metafields.lens.optical_stabilization | default: '' %}
{% assign lens_sealed = product.metafields.lens.weather_sealed | default: false %}
{% assign lens_zoom_type = product.metafields.lens.zoom_type | default: '' %}
{% assign lens_compatible_group = product.metafields.lens.compatible_body_group | default: '' %}
{% assign lens_compatible_url = product.metafields.lens.compatible_body_url | default: '' %}


{% endif %}

Metafield definitions for your Shopify store (namespace: lens):

5 common mistakes

FAQ

Should I use isAccessoryOrSparePartFor to link to every individual camera body, or to a ProductGroup?

For third-party lenses and first-party lenses that fit all bodies with a given mount, link to a ProductGroup representing the full mount ecosystem — e.g., "Canon RF Full-Frame Mirrorless Cameras". This is lower maintenance and correctly captures the full compatibility scope. Reserve individual Product links within compatibleWith for bodies where you've explicitly verified compatibility. The distinction: isAccessoryOrSparePartFor establishes the category relationship ("this is a Canon RF lens"), while compatibleWith lists verified specific models ("confirmed working on EOS R5 Mark II, R6 Mark II, R3"). Both together give AI agents the broad filter and the confidence check.

How do I handle a third-party lens available in multiple mounts — one product or one per mount?

One Shopify product per mount variant. A Sigma 35mm f/1.4 Art for Canon RF and the same lens for Sony FE are different products from the perspective of every compatibility signal — mount, image circle coverage, autofocus protocol, and compatibleWith bodies all differ. Using product variants for mount selection forces the isAccessoryOrSparePartFor to be ambiguous across all mount variants simultaneously, which breaks the compatibility filter. Create separate products with separate mount-specific ProductGroup references.

How do I encode an APS-C format lens so AI agents warn buyers with full-frame bodies?

Two signals create the machine-readable warning: (1) Set "Image Circle Coverage" to "APS-C only (28.4mm circle — not compatible with full-frame 36×24mm sensor without vignetting)". The word "vignetting" is the key term AI agents parse to surface the incompatibility warning. (2) Scope isAccessoryOrSparePartFor to APS-C bodies only — "Sony APS-C Mirrorless Cameras (E-Mount, APS-C)" rather than the broader E-Mount ecosystem. Without this scope restriction, an AI agent sees "Sony E-Mount" and considers the lens compatible with all E-Mount bodies including full-frame A7.

What is the difference between isAccessoryOrSparePartFor and compatibleWith for camera lenses?

isAccessoryOrSparePartFor establishes what product category this is an accessory for — "what mount ecosystem does this lens belong to?" at a category level. It typically points to a ProductGroup. compatibleWith lists specific products that have been confirmed to work together — "which exact camera models does this work with?" Use both. isAccessoryOrSparePartFor without compatibleWith gives mount scope but no model-level confidence. compatibleWith without isAccessoryOrSparePartFor buries the mount relationship inside a list of body names that AI agents must reverse-engineer.

Should I encode adapter compatibility for Canon EF lenses on Canon RF bodies?

Yes — adapter compatibility is a significant buyer pool. For Canon EF lenses, add a second isAccessoryOrSparePartFor referencing "Canon RF Mirrorless Bodies (via Mount Adapter EF-EOS R)" and add an additionalProperty "RF Adapter Compatible: Yes — Canon Mount Adapter EF-EOS R (sold separately; all EF functions including IS and autofocus are retained with the official Canon adapter)." For Nikon F lenses, encode the AF motor caveat: AF-S/AF-I lenses autofocus via FTZ II adapter; older screwdriver-drive AF lenses do not. This prevents returns from buyers who expected full adapter parity across all legacy Nikon F lenses.