The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 45mm F1.8 Di VC USD and the Sigma 50mm F1.4 DG HSM A 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 50mm F1.4 DG HSM A is the longer of the two lenses at 100mm. The Tamron 45mm F1.8 Di VC USD with a length of 92mm is 8mm shorter. Besides being longer, the Sigma 50mm F1.4 DG HSM A also has a larger diameter of 85mm compared to Tamron 45mm F1.8 Di VC USD's 80mm 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 45mm F1.8 Di VC USD weighs 520g, which means it is 295g (36%) lighter than the Sigma 50mm F1.4 DG HSM A which has a weight of 815g.
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
Lens Mounts
Both Tamron 45mm F1.8 Di VC USD and Sigma 50mm F1.4 DG HSM A 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.
Sigma 50mm F1.4 DG HSM A is also available in Canon EF , Sigma SA, Nikon F (FX) and Leica L mounts.
Focal Range
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.
Sigma 50mm F1.4 DG HSM A is a prime lens with fixed focal lenght of 50mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 75mm.