Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Tamron 45mm F1.8 Di VC USD is the longer of the two lenses at 92mm. The Sony DT 50mm F1.8 SAM with a length of 45mm is 47mm shorter. Besides being longer, the Tamron 45mm F1.8 Di VC USD also has a larger diameter of 80mm compared to Sony DT 50mm F1.8 SAM's 70mm 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 50mm F1.8 SAM weighs 170g, 205% (350g) lighter than the Tamron 45mm F1.8 Di VC USD's weight of 520g.
Below you can find the dimension and weight table of the 'Standard Prime Lenses in Sony Alpha Mount for size comparison purposes.
Standard Prime Lenses in Sony Alpha Mount for Size Comparison
Both Tamron 45mm F1.8 Di VC USD and Sony DT 50mm F1.8 SAM 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 45mm F1.8 Di VC USD is also available in Canon EF and Nikon F (FX) mounts.
Tamron 45mm F1.8 Di VC USD is a prime lens with fixed focal lenght of 45mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 67.5mm.
Sony DT 50mm F1.8 SAM is a prime lens with fixed focal lenght of 50mm which has a 35mm equivalent focal range of 67.5mm when used on a APS-C / DX format camera.