Details: Recommended Sensor size: APS-C 1.6x Crop Factor (Full-frame Fisheye)' Maximum Aperture: F/3.5-4.5 Minimum Aperture: F/22 Optical Construction: 10 Elements / 8 Groups Coatings: Multi-layer Coatings Front element of the AT-X 107 DX has a newly formulated WP or "Water Proof" optical coating on the glass