Tokina AT-X 100-300mm f/4 (IF) is a versatile, telephoto zoom lens designed for Nikon SLR and DSLRs. The high quality internal focusing (IF) lens employs high quality optics and a fast, constant f/4 aperture throughout the entire zoom range. In addition, this lens has a 15 elements in 11 groups with one SD glass element, a mere 6.6ft close focusing distance (is very sharp throughout the focal length range), nine blade diaphragm, 24-8° viewing angle and 77mm filter thread.
When mounted to a CCD sensor camera the 100-300mm f/4 becomes 150-450mm maintaining the constant f/4 aperture. The CCD sensor captures the image at the time of shutter release. The image is 50% smaller than the standard 35mm transparency. The end results are an increase in the effective focal length any given lens by 50% while maintaining the same baseline aperture.