The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron AF 18-270mm f3.5-6.3 II VC LD and the Sigma 18-250mm F3.5-6.3 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.Tamron AF 18-270mm f3.5-6.3 II VC LD is the longer of the two lenses at 101mm. The Sigma 18-250mm F3.5-6.3 DC OS HSM with a length of 89mm is 12mm shorter. Besides being longer, the Tamron AF 18-270mm f3.5-6.3 II VC LD also has a larger diameter of 80mm compared to Sigma 18-250mm F3.5-6.3 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 18-250mm F3.5-6.3 DC OS HSM weighs 470g, 16% (90g) lighter than the Tamron AF 18-270mm f3.5-6.3 II VC LD's weight of 560g.
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 Tamron AF 18-270mm f3.5-6.3 II VC LD and Sigma 18-250mm F3.5-6.3 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.
Tamron AF 18-270mm f3.5-6.3 II VC LD is also available in Nikon F (DX) mount.
Sigma 18-250mm F3.5-6.3 DC OS HSM is also available in Nikon F (DX) , Pentax KAF3, Sony Alpha, Sigma SA, Canon EF, Nikon F (DX), Pentax KAF3, Sony Alpha and Sigma SA mounts.
Focal Range
Tamron AF 18-270mm f3.5-6.3 II VC LD has a focal range of 18-270mm and 15.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-432mm when used on a APS-C / DX format camera. Sigma 18-250mm F3.5-6.3 DC OS HSM has a focal range of 18-250mm and 13.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-400mm when used on a APS-C / DX format camera.