Lens Cap Sizes: 37, 40.5, and 46 mm Compared
By BRAUN Photo Technik Germany – Seit 1915 | Published: 2026-10-21
Category: Comparisons
Choosing the right lens cap size matters. We compare 37 mm, 40.5 mm, and 46 mm caps to help you match your lens or filter thread.
Quick Answer
Choose the cap that matches the filter thread diameter printed on your lens or filter. For 37 mm, 40.5 mm, and 46 mm threads, BRAUN offers dedicated caps with a secure center-clip fit.
Why the exact diameter matters
A lens cap is not a one-size-fits-all accessory. The number in millimeters refers to the filter thread diameter on the front of your lens. If you use a cap that is too large, it will fall off; too small, and it won't attach at all.
Check the front of your lens or the lens cap that came with it. The diameter is usually printed with a 'Ø' symbol (for example, Ø37). If you use a filter, the cap should match the filter's thread size, not the lens's bare thread.
Common lenses for these sizes
37 mm is often found on compact prime lenses and some older film cameras. 40.5 mm is common on small mirrorless primes and some compact cameras. 46 mm appears on standard zoom lenses and some fast primes.
If you own multiple lenses with different thread sizes, you may need a separate cap for each. Buying the correct size the first time saves you the hassle of returns.
How to Choose the Right Size
- 37 mm cap: Use this size for lenses with a 37 mm filter thread. It's a compact cap that suits small primes and some vintage lenses. Confirm the thread size on the lens barrel before ordering.
- 40.5 mm cap: This size fits lenses with a 40.5 mm thread, a common choice for mirrorless prime lenses. It offers a snug fit without adding bulk. If you use a filter, match the cap to the filter's thread, not the lens's bare thread.
- 46 mm cap: Choose this size for lenses with a 46 mm thread, often found on standard zooms. It provides a larger protective cover for the front element. When in doubt, check the diameter printed on the lens cap or lens barrel.
BRAUN Lens Caps at a Glance
- BRAUN Professional Objektivdeckel 37 mm: BRAUN Professional Objektivdeckel 37 mm fits lenses and filters with a 37 mm filter thread. Ideal for compact primes or vintage lenses that use the smaller 37 mm thread.
BRAUN Professional Objektivdeckel 37 mm - BRAUN Professional Objektivdeckel 40.5 mm: BRAUN Professional Objektivdeckel 40.5 mm fits lenses and filters with a 40.5 mm filter thread. A common size for small mirrorless primes, so check your lens before buying.
BRAUN Professional Objektivdeckel 40.5 mm - BRAUN Professional Objektivdeckel 46 mm: BRAUN Professional Objektivdeckel 46 mm fits lenses and filters with a 46 mm filter thread. Often found on standard zooms; a secure fit protects the front element from dust and scratches.
Which Cap Fits You?
Best for
- Photographers with a compact prime lens that uses a 37 mm thread
- Mirrorless shooters with a small 40.5 mm filter thread
- Users of standard zoom lenses with a 46 mm thread
Not for
- Lenses with larger filter threads (e.g., 49 mm or 52 mm) – these caps won't fit
- Caps without a center clip – if you prefer a pinch-style cap, consider other options
