The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 100-400mm F5-6.3 OS and the Tamron 70-180mm F2.8 Di for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is an important deciding factor when comparing two lenses. Sigma 100-400mm F5-6.3 OS is the longer of the two lenses at 197mm. The Tamron 70-180mm F2.8 Di with a length of 149mm, is 48mm shorter. Besides being longer, the Sigma 100-400mm F5-6.3 OS also has a larger diameter of 86mm compared to the Tamron 70-180mm F2.8 Di's 81mm diameter.
Below you can find a scaled side-by-side image of Sigma 100-400mm F5-6.3 OS and Tamron 70-180mm F2.8 Di to get a better idea of how their sizes compare in real life.
Comparison image of the Sigma 100-400mm F5-6.3 OS and the Tamron 70-180mm F2.8 Di Size and Weight The 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 70-180mm F2.8 Di weighs 815g, 28% (320g) lighter than the Sigma 100-400mm F5-6.3 OS's weight of 1135g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Sony E Mount for size comparison purposes.
Telephoto Zoom Lenses in Sony E Mount for Size Comparison
Lens Mounts
Both the Sigma 100-400mm F5-6.3 OS and the Tamron 70-180mm F2.8 Di has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony A7R V, Sony FX30 and Sony A7 IV.
Sigma 100-400mm F5-6.3 OS is also available in Leica L mount.
Focal Range
Sigma 100-400mm F5-6.3 OS has a focal range of 100-400mm and 4.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 150 - 600mm.
Tamron 70-180mm F2.8 Di has a focal range of 70-180mm and 2.6X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 105 - 270mm.