The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron AF 55-200mm f4-5.6 II LD and the Sigma 70-200mm F2.8 EX DG OS HSM for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sigma 70-200mm F2.8 EX DG OS HSM is the longer of the two lenses at 197mm. The Tamron AF 55-200mm f4-5.6 II LD with a length of 83mm is 114mm shorter. Besides being longer, the Sigma 70-200mm F2.8 EX DG OS HSM also has a larger diameter of 86mm compared to Tamron AF 55-200mm f4-5.6 II LD's 72mm diameter.
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. Tamron AF 55-200mm f4-5.6 II LD weighs 300g, which means it is 1130g (79%) lighter than the Sigma 70-200mm F2.8 EX DG OS HSM which has a weight of 1430g.
Below you can find the dimension and weight table of the 'Telephoto Zoom Lenses in Sony Alpha Mount for size comparison purposes.
Telephoto Zoom Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both Tamron AF 55-200mm f4-5.6 II LD and Sigma 70-200mm F2.8 EX DG OS HSM has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A68, Sony A77 II and Sony A58.
Tamron AF 55-200mm f4-5.6 II LD is also available in Canon EF and Nikon F (DX) mounts.
Sigma 70-200mm F2.8 EX DG OS HSM is also available in Canon EF , Nikon F (FX), Pentax KAF3 and Sigma SA mounts.
Focal Range
Tamron AF 55-200mm f4-5.6 II LD has a focal range of 55-200mm and 3.6X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 82.5-300mm when used on a APS-C / DX format camera. Sigma 70-200mm F2.8 EX DG OS HSM has a focal range of 70-200mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 105 - 300mm.