The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tokina 16.5-135mm f3.5-5.6 DX and the Sigma 18-125mm F3.8-5.6 DC OS HSM 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 18-125mm F3.8-5.6 DC OS HSM is the longer of the two lenses at 89mm. The Tokina 16.5-135mm f3.5-5.6 DX with a length of 78mm is 11mm shorter. On the other hand, the Tokina 16.5-135mm f3.5-5.6 DX has a larger diameter of 84mm compared to Sigma 18-125mm F3.8-5.6 DC OS HSM's 74mm 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. Sigma 18-125mm F3.8-5.6 DC OS HSM weighs 490g, 19% (120g) lighter than the Tokina 16.5-135mm f3.5-5.6 DX's weight of 610g.
Below you can find the dimension and weight table of the 'SuperZoom Lenses in Canon EF Mount for size comparison purposes.
SuperZoom Lenses in Canon EF Mount for Size Comparison
Lens Mounts
Both Tokina 16.5-135mm f3.5-5.6 DX and Sigma 18-125mm F3.8-5.6 DC OS HSM has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon T8i, Canon 90D and Canon SL3.
Tokina 16.5-135mm f3.5-5.6 DX is also available in Nikon F (DX) mount.
Sigma 18-125mm F3.8-5.6 DC OS HSM is also available in Sigma SA and Nikon F (DX) mounts.
Focal Range
Tokina 16.5-135mm f3.5-5.6 DX has a focal range of 17-135mm and 7.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27.2-216mm when used on a APS-C / DX format camera. Sigma 18-125mm F3.8-5.6 DC OS HSM has a focal range of 18-125mm and 6.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-200mm when used on a APS-C / DX format camera.