Breakthrough Photography 77mm X1 UV Flat Black Filter, Multi-Coated, 3.5mm Ultra Slim Weather Sealed Frame

Great as a backup or even as a primary filter, the Breakthrough Photography X1 is a solid performer that should always be at the ready in the event you'll be shooting on-the-go in a number of different environments. Aimed at professional as well as amateur photographers, the latest X-Series filter lineup features an innovative Traction frame design with state-of-the-art optics and coatings. X1 Flat Black Filters feature an ultra-slim 3.5mm standard flat black frame with MRC4.

Optics
In addition to having great optical performance, X1 features state-of-the-art multi-resistant coating. Two layers of MRC are applied to each side of the optical disk, resulting in a total of MRC-4. In addition to being structurally harder than glass itself, an MRC coating increases light transmittance and prevents common flaring, ghosting, low-contrast and all the rest. In dusty environments a UV filter can help protect the front lens element and complete the lens weather-sealing

The use of uncoated filters is not recommended as glass without MRC coatings are highly susceptible to a range of optical phenomenon such as flaring, ghosting (lower contrast as a result) and generally less saturation. When glass is introduced in front of the lens it lowers the resolving power of the lens down to that of the filter.

Thin and light. Yet rock solid.
The X1 features a 3.5mm ultra-slim double-threaded frame profile to eliminate vignetting on wide-angle full-frame setups. Why 3.5mm

Tests show that the 4mm is the frame width at which point vignetting become noticeable on 16mm wide-angle setups on full-frame cameras. But any lower than 3 and lens caps and such don't stay on. At 3.7mm vignetting was entirely eliminated.

Double-Threaded & Laser Engraved.
X1's 3.5mm frame still accepts all lens caps just fine but also stays below the 3.7mm. Laser engraved lettering in the X1's standard flat black frame ensure that the lettering won't ever fade or come off after consistent use. Breakthrough also engraves each and every X1 UV Filter frame with a unique serial number.

When you activate your 25 Year Ironclad Guarantee, Breakthrough associates your X1 serial number to you, so any future discussions on this unique filter are tracked, issues recorded and all that stuff which goes into future product design.

Weather-sealed durability.
If you want to ensure that your lens maintains out-of-box optical performance for as long as possible, Canon, Nikon and Sony recommend protective filters for the purpose of completing a lens weather-seal. Without a filter, the lens is not dust or water resistant, as Canon states on page 2 of their lens user manuals.