The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 85mm F1.8 VC and the Canon 100mm f2.8 Macro USM 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. Canon 100mm f2.8 Macro USM is the longer of the two lenses at 119mm. The Tamron 85mm F1.8 VC with a length of 91mm, is 28mm shorter. On the other hand, the Tamron 85mm F1.8 VC has a larger diameter of 85mm compared to the Canon 100mm f2.8 Macro USM's 79mm diameter.
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. Canon 100mm f2.8 Macro USM weighs 600g, 14% (100g) lighter than the Tamron 85mm F1.8 VC's weight of 700g.
Lens Mounts
Both the Tamron 85mm F1.8 VC and the Canon 100mm f2.8 Macro USM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Tamron 85mm F1.8 VC is also available in Sony Alpha and Nikon F (FX) mounts.
Focal Range
Tamron 85mm F1.8 VC is a prime lens with fixed focal lenght of 85mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 136mm.
Canon 100mm f2.8 Macro USM is a prime lens with fixed focal lenght of 100mm. When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 160mm.