The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron AF 18-250mm f3.5-6.3 II LD and the Sigma 18-300 F3.5-6.3 DC OS HSM for their suitability to various photography scenarios:
Size and Weight Comparison
The size of a lens is a crucial factor to consider when comparing two lenses. Sigma 18-300 F3.5-6.3 DC OS HSM is the longer of the two lenses at 102mm. The Tamron AF 18-250mm f3.5-6.3 II LD with a length of 84mm, is 18mm shorter. Besides being longer, the Sigma 18-300 F3.5-6.3 DC OS HSM also has a larger diameter of 79mm compared to the Tamron AF 18-250mm f3.5-6.3 II LD's 74mm diameter.
The weight of a lens is equally significant as its external dimensions, particularly if you intend to handhold your camera and lens combination for extended periods. Tamron AF 18-250mm f3.5-6.3 II LD weighs 430g, which means it is 155g (26%) lighter than the Sigma 18-300 F3.5-6.3 DC OS HSM which has a weight of 585g.
Below you can find the dimension and weight table of the SuperZoom Lenses in Canon EF Mount for size comparison purposes.
Super Telephoto Lenses in Canon EF Mount for Size Comparison
Filter Threads
The Tamron AF 18-250mm f3.5-6.3 II LD has a filter size of 62mm whereas the Sigma 18-300 F3.5-6.3 DC OS HSM has a 72mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 62mm filters that we recommend you to consider for the Tamron AF 18-250mm f3.5-6.3 II LD:
And these are the 72mm filters that we recommend for the Sigma 18-300 F3.5-6.3 DC OS HSM:
Lens Mounts
Both the Tamron AF 18-250mm f3.5-6.3 II LD and the Sigma 18-300 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 18-250mm f3.5-6.3 II LD is also available in Nikon F (DX) , Sony Alpha and Pentax KAF mounts.
Sigma 18-300 F3.5-6.3 DC OS HSM is also available in Nikon F (DX) , Pentax KAF3, Sigma SA and Sony Alpha mounts.
Focal Range
Tamron AF 18-250mm f3.5-6.3 II LD 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.
On the other hand, the Sigma 18-300 F3.5-6.3 DC OS HSM has a focal range of 18-300mm and 16.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-480mm when used on a APS-C / DX format camera.