Tiffen Letterbox 30mm Diopter

A unique filter - the so-called Spark.

Letter Box Diopters are considered the opposite of Strip Diopters. The open slot in the center (similar to the slot in a mailbox / letter box) is surrounded by diopter glass on both sides. These diopters allow you to create interesting effects when experimenting and allow you to achieve varying effects of focus, diffusion and double imaging. They come in 15mm and 30mm formats.