The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 70-300mm F4-5.6 DG and the Pentax 50-200mm F4-5.6 ED for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Sigma 70-300mm F4-5.6 DG is the longer of the two lenses at 122mm. The Pentax 50-200mm F4-5.6 ED with a length of 80mm, is 42mm shorter. Besides being longer, the Sigma 70-300mm F4-5.6 DG also has a larger diameter of 77mm compared to the Pentax 50-200mm F4-5.6 ED's 69mm diameter.
The weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Pentax 50-200mm F4-5.6 ED weighs 272g, 50% (278g) lighter than the Sigma 70-300mm F4-5.6 DG's weight of 550g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Pentax KAF Mount for size comparison purposes.
Telephoto Zoom Lenses in Pentax KAF Mount for Size Comparison
Both the Sigma 70-300mm F4-5.6 DG and the Pentax 50-200mm F4-5.6 ED has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax KF, Pentax K-3 III and Pentax K-1 II.
Sigma 70-300mm F4-5.6 DG is also available in Canon EF , Nikon F (FX), Sony Alpha, Sigma SA, Canon EF, Nikon F (FX), Pentax KAF, Sony Alpha and Sigma SA mounts.
Sigma 70-300mm F4-5.6 DG has a focal range of 70-300mm and 4.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 105 - 450mm.
Pentax 50-200mm F4-5.6 ED has a focal range of 50-200mm and 4.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 75-300mm when used on a APS-C / DX format camera.