Schneider 138mm Diopters are high-quality single element close-up lenses that require absolutely no exposure compensation. These diopters are protected by a unique mount which ensures superb structural integrity and consistent long-term performance, even in demanding production environments.These Diopters are made from the finest optical glass. They feature Schneider’s hard, anti-reflective coating on both front and rear surfaces; measurably reducing light loss and flare while helping to ensure proper colour, contrast and overall image quality. These diopters shorten the close-focusing distance of normal fixed focal length or zoom lenses. This allows the camera to focus closer to the subject and achieve a larger image size while bringing out the sharpest details in even the tiniest subjects.These Diopters are available in strengths of +0.5, +1.0, +2.0 and +3.0. These diopters increase the minimum working distance, enabling closer focus from a greater working distance. Calculation of strength depends on focal length, focus setting, object distance, and size.