Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sony 75-300mm F4.5-5.6 is the longer of the two lenses at 122mm. The Tamron AF 70-300mm f4-5.6 LD with a length of 117mm is 5mm shorter. On the other hand, the Tamron AF 70-300mm f4-5.6 LD has a larger diameter of 77mm compared to Sony 75-300mm F4.5-5.6's 71mm 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 70-300mm f4-5.6 LD weighs 435g, which means it is 25g (5%) lighter than the Sony 75-300mm F4.5-5.6 which has a weight of 460g.
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 70-300mm f4-5.6 LD and Sony 75-300mm F4.5-5.6 has the same Sony Alpha lens mount. Some of the latest released cameras that are compatible with the Sony Alpha lenses are Sony A99 II, Sony A68 and Sony A77 II.
Tamron AF 70-300mm f4-5.6 LD is also available in Canon EF , Nikon F (FX) and Pentax KAF mounts.
Focal Range
Tamron AF 70-300mm f4-5.6 LD 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 an 35mm (FF) equivalent of 105 - 450mm.
Sony 75-300mm F4.5-5.6 has a focal range of 75-300mm and 4.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 112.5 - 450mm.