138mm Letterbox Diopter Strength:1 The addition of a quarter

The addition of a quarter wave plane is to circularly polarize linearly polarized light for the use of auto focus and exposure functions

Class 1 product specifications AA-50177

It creates a darkening of the entire image

Supports most tripods with dual spiked feet and many tripods with rubber feet

138mm Letterbox Diopter Strength:1 The addition of a quarterLetter 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.