138mm Letterbox Diopter Strength:3 Absorbs 86% of UV light

Absorbs 86% of UV light and reduces bluish cast of daylight

Alleviating the need to use multiple filters at once

Superior Quality

function as a twist on the stand of the pro halation spill effect

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138mm Letterbox Diopter Strength:3 Absorbs 86% of UV lightLetter Box Diopters are considered the reverse of the Strip Diopters. An open slot in the center (similar to a slot in a mail letter box) is flanked by diopter glass on either side. These diopters allow you to create interesting effects while experimenting and allow you to achieve varied focus, diffusion and double imaging effects. They come in 15mm and 30mm formats.