The Pentax smc FA 645 33-55mm f/4.5 AL Lens is a wide-angle zoom lens designed for use with medium format Pentax 645 mount cameras. It features an aperture range of f/4.5-32 and has a 35mm equivalent focal length of 26-43.5mm, providing a very useful range of wide-angle lengths. This lens in particular utilizes two aspherical elements that greatly reduce distortion, field curvature, and coma aberrations common with wide angle lenses.
The 33-55mm features a lens construction of 11 elements in 8 groups, including some high refraction low-dispersion glass. To maintain image quality, it uses a 3-group floating zoom to reduce field curvature throughout the range. Also, the 33-55mm has a minimum focus distance of 15.7".
For smooth out-of-focus areas, the lens has an eight blade aperture diaphragm. Additionally, it features an 82mm front filter thread.
35mm focal length equivalent of 26-43.5mm
Aperture range of f/4.5 to f/32
Angle of view of 80° to 53° which equates to 65° to 43° on Pentax 645 digital cameras
Lens construction of 11 elements in 8 groups
Low-dispersion glass elements help to minimize chromatic aberrations and maximize sharpness
Accepts 82mm threaded filters
Minimum focusing distance throughout the zoom range is 15.7"
Super Multi Coating increases light transmission as well as helps to eliminate ghosting and flaring
Works with both film and digital formats
Aperture ring and focusing distance scale
Eight diaphragm blades for smooth out-of-focus areas