40.5MM Polarising Filter Circular Polarizing CPL, Ultra Slim, Japan Optics, Multi Coated

SKU: KF01.1307

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new technology i guess, cnc Trapezoidal thread forms are screw thread profiles with trapezoidal outlines which helps more friction when screwing. Very easy to install. 
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hello , the more expensive filter is Nano coating and scratch-resistant. this filter only Multi Coated, it is helping repel water, dust but no scratch-resistant. the 82mm filter for 77mm lens, you need a 77-82 mm filter adapter.like this item 
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yes, the same size lens cap could attach to the cpl filter and stay secure 
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Try a different lighting setting. 90° from the sun to darken skies or solar reflections will be effected with a polarizer filter. I’m not sure what the seller means from their reply. 
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hello, The K&F Polarizers Filter Multi Resistance Coating (MRC) helping repel water, dust & grease, while also preventing ghosting