Letter 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.
- Strength: +1, +2, +3
- Format: 15mm, 30mm