49mm filter adapter

Screw on standard 49mm filters. The III, IIIx and IV each take a different adapter, and all three mount securely: NiSi's GR III and IIIx parts lock. NiSi's GR IV part is off Amazon on its own right now (it ships inside NiSi's GR IV wide kit), so the GR IV button goes to JJC's bayonet equivalent.

The adapter route is for anyone who wants real screw-in filters - ND, black mist, CineBloom, polarizer - without committing to a full hood. Fit depends on which body you shoot. NiSi's MK II parts for the GR III (PR-11) and GR IIIx (PR-12) have a proper locking design - a slide control locks the adapter to the body. That matters: NiSi's older GR III adapter was friction-fit, and the community has detach stories about it (one straight onto concrete), so if you are buying used, make sure it is the MK II. While NiSi's GR IV part (PR-8) is off Amazon, the GR IV button substitutes JJC's GA-3-style bayonet adapter - a secure mount, though without the genuine GA-3's WIDE auto-detect. The III, IIIx and IV parts are not interchangeable.

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