The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 24-70mm f2.8 VC USD and the Sony DT 18-55mm F3.5-5.6 SAM II for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Tamron 24-70mm f2.8 VC USD is the longer of the two lenses at 117mm. The Sony DT 18-55mm F3.5-5.6 SAM II with a length of 69mm is 48mm shorter. Besides being longer, the Tamron 24-70mm f2.8 VC USD also has a larger diameter of 88mm compared to Sony DT 18-55mm F3.5-5.6 SAM II'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. Sony DT 18-55mm F3.5-5.6 SAM II weighs 222g, 73% (603g) lighter than the Tamron 24-70mm f2.8 VC USD's weight of 825g.
Below you can find the dimension and weight table of the 'Standard Zoom Lenses in Sony Alpha Mount for size comparison purposes.
Standard Zoom Lenses in Sony Alpha Mount for Size Comparison
Lens Mounts
Both Tamron 24-70mm f2.8 VC USD and Sony DT 18-55mm F3.5-5.6 SAM II 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 24-70mm f2.8 VC USD is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
Tamron 24-70mm f2.8 VC USD has a focal range of 24-70mm 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 36 - 105mm.
Sony DT 18-55mm F3.5-5.6 SAM II has a focal range of 18-55mm and 3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-82.5mm when used on a APS-C / DX format camera.