The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony 28mm F2.8 and the Sony 20mm F2.8 for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Sony 20mm F2.8 is the longer of the two lenses at 54mm. The Sony 28mm F2.8 with a length of 43mm is 11mm shorter. Besides being longer, the Sony 20mm F2.8 also has a larger diameter of 78mm compared to Sony 28mm F2.8's 66mm 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 28mm F2.8 weighs 185g, which means it is 100g (35%) lighter than the Sony 20mm F2.8 which has a weight of 285g.
Below you can find the dimension and weight table of the 'Wideangle Prime Lenses in Sony Alpha Mount for size comparison purposes.
Wideangle Prime Lenses in Sony Alpha Mount for Size Comparison
Both Sony 28mm F2.8 and Sony 20mm F2.8 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.
Sony 28mm F2.8 is a prime lens with fixed focal lenght of 28mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 42mm.
Sony 20mm F2.8 is a prime lens with fixed focal lenght of 20mm. When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 30mm.