Scope: bags, cases, pouches and straps that carry, protect, or attach cameras and lenses (backpacks, shoulder/messenger bags, sling bags, holster bags, hard/rolling cases, lens pouches, straps); excludes camera accessories/parts (filters, tripods, cleaning kits — sibling leaf camera-accessories).

Seed:
1. The weave-equivalent here is liters-as-trap: the number every listing leads with doesn't say what fits or how it carries; the real axes are divider/harness/latch system (customizable dividers vs fixed, hip belt vs sling, IP-rated hard shell vs DWR-coated fabric) — two 20L bags with different harnesses and access styles protect and carry totally differently.
2. A reliability-minded buyer checks first whether "weatherproof" is backed by a tested standard (an IP number) or is just marketing words with no test behind it, and whether capacity is a real "fits 1 body + X lenses" spec rather than a bare liter count.

Sources:
[wikipedia_camera_bag] https://en.wikipedia.org/wiki/Camera_bag — camera bag history/mechanism — fetched excerpt: "In the 1970s... Billingham noticed their waterproof soft bags were popular with photographers and modified the fishing bag with padding"
[wikipedia_ip_code] https://en.wikipedia.org/wiki/IP_Code — IP67 definition — fetched excerpt: "Immersion, up to 1 meter... Test duration: 30 minutes" / digit 6 "Dust-tight"
[wikipedia_road_case] https://en.wikipedia.org/wiki/Road_case — hard case foam/wheels construction — fetched excerpt: "foam has cavities that correspond to the shape of the components" / "Caster wheels are often built into... telescoping handles"
[wikipedia_baggage_allowance] https://en.wikipedia.org/wiki/Baggage_allowance — IATA carry-on size — fetched excerpt: "suitcases should have a maximum size of 55 cm... 35 cm wide and 20 cm... deep"
[thinktank_backlight_sprint] https://www.thinktankphoto.com/products/backlight-sprint — backpack spec sheet — fetched excerpt: "Exterior Dimensions:... Volume: 15 Liters" / "durable water-repellant coating... YKK RC-Fuse zippers, 420D velocity nylon"
[thinktank_walker_pro_24l] https://www.thinktankphoto.com/products/walker-pro-24l — backpack spec sheet — fetched excerpt: "Total Volume: 24 Liters... Weight:... 1.56 kg" / "Nylon 1680D Ballistics... Durable water-repellant (DWR) coating" / "Customizable divider system" / sternum strap image caption
[nanuk_920] https://nanuk.com/products/nanuk-920 — hard case spec sheet — fetched excerpt (JSON-LD): "Exterior Dimensions... Weight (Empty)... Waterproof Rating: IP67" / description: "automatic pressure release valve" / "cubed foam, custom foam, padded dividers" / sibling collection "Carry-On Cases" and "935 with Heavy Duty Wheels" variant names
[dcw_straps] https://www.digitalcameraworld.com/buying-guides/the-best-camera-straps — strap buyer's guide — fetched excerpt: "Material: Neoprene pad, nylon webbing, plastic, leather... Webbing width: 1/4" or 3/4""
[shuttermuse_anchor_guide] https://shuttermuse.com/peak-design-anchor-links-and-connectors/ — specialist reviewer — fetched excerpt: "The current Anchors have a load rating of 200 lbs (90 kg)" / "quick-release system"
[popphoto_lens_cases] https://www.popphoto.com/story/reviews/best-camera-lens-case/ — specialist reviewer — fetched excerpt: "neoprene cases... water-resistant... drawstring close" / "lens pouch with belt loops will allow you to store the lens on your hip"

Branches:
- product_type → backpack/shoulder/sling/holster ask soft-bag facets, hard_case asks IP/shell/foam/mobility, lens_pouch asks closure/material, strap asks attachment/material: supported by the facet-set split across thinktank_backlight_sprint (soft bag specs) vs nanuk_920 (hard case specs) vs popphoto_lens_cases (pouch specs) vs dcw_straps (strap specs) — four genuinely different spec vocabularies confirm the fork.
- capacity_need minimal_kit makes mobility irrelevant: a 1-body kit rarely needs a rolling hard case; reasoning call, not directly sourced.
- environment_demand foul_weather_or_fieldwork asks weatherproofing_level + ingress_protection_rating: supported by thinktank_backlight_sprint (DWR tier) and wikipedia_ip_code/nanuk_920 (IP tier) being the two different weatherproofing vocabularies in the research.

Noise (spec-sheet rows seen, no facet):
- Color/colorway options (thinktank, nanuk) — not expertise, price/aesthetic only.
- Price, financing terms, SKU/GTIN (nanuk, thinktank) — excluded per rule (price is never a facet).
- Laptop sleeve dimensions (thinktank_walker_pro_24l) — amenity, not a core comparison axis for a camera bag.
- Buoyancy rating and operating temperature range (nanuk_920, via search snippets only, not independently fetched-confirmed with two sources) — niche, dropped for lack of two-source confirmation and limited buyer relevance.
- Exact strap load rating in kg/lbs (dcw_straps: 66kg; shuttermuse: 200lbs) — each number is single-product-sourced; kept strap_attachment_style qualitative instead of asserting a universal numeric load range.
- ATA Spec 300 flight-case certification — mentioned in category research context but not found in the fetched wikipedia_road_case text; left out rather than cited unseen.

Corrections:
- derived_metrics/0 needed depends_on + why (not why_it_matters); renamed/added. product_type priority.narrows_set capped at 5 (was 6). references kind 'reviewer' → 'specialist_review' (schema enum).

Corrections (2026-10-26):
- environment_demand's foul_weather_or_fieldwork branch no longer asks ingress_protection_rating directly; product_type's own hard_case branch is now the sole gate for that facet, removing the contradiction with every soft-bag makes_irrelevant list.
- Added empty_weight_kg as a numeric facet (sourced to the two Think Tank spec sheets already cited) and made derived_metrics[0].depends_on include it, so bag_weight_per_liter is computable from facets the register defines.
- Added capacity_need to product_type's lens_pouch and strap makes_irrelevant lists so the kit-size question stops firing for single-lens pouches and straps.
- Added lockable_closure facet (padlock eyelets / lockable zipper pulls), re-fetched and grepped directly from thinktank_walker_pro_24l ("Lockable zipper on main camera compartment") and nanuk_920 ("reinforced metal padlock eyelets"); added "Padlock eyelets" to vocabulary.
- Added laptop_compartment facet, sourced to a newly fetched peakdesign_edb spec sheet ("sleeves for up to 15in laptop (or 16in MacBook Pro)") and thinktank_walker_pro_24l's padded laptop sleeve.
- Re-fetched and grepped an Amazon retail listing for the Walker Pro 24L (new ref amazon_walker_pro_listing): title states "24L", description confirms a "harness system" and "attachment points for tripods" — independently confirming capacity_liters, carry_harness, and tripod_carry as genuine retail-listing fields, so those three keep source:listing. The other ten facets previously marked source:listing on brand/specialist evidence only (divider_system, exterior_fabric, ingress_protection_rating, shell_material, foam_or_divider_system, mobility, pouch_closure, pouch_material, strap_attachment_style, strap_material) are relabeled source:researched.
- Defined "Cubed foam", "Tripod mount", and "Sling clip" in vocabulary; added a clause to shell_material's why_experts_care distinguishing abs_polycarbonate (stiffer, more prone to cracking at hinges) from polymer_resin instead of treating them as identical.