The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Canon 100-400mm f4.5-5.6L IS II USM and the Tamron AF 18-250mm f3.5-6.3 II LD 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. Canon 100-400mm f4.5-5.6L IS II USM is the longer of the two lenses at 193mm. The Tamron AF 18-250mm f3.5-6.3 II LD with a length of 84mm, is 109mm shorter. Besides being longer, the Canon 100-400mm f4.5-5.6L IS II USM also has a larger diameter of 94mm 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, 72% (1160g) lighter than the Canon 100-400mm f4.5-5.6L IS II USM's weight of 1590g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Canon EF Mount for size comparison purposes.
Super Telephoto Lenses in Canon EF Mount for Size Comparison
Filter Threads
The Canon 100-400mm f4.5-5.6L IS II USM has a filter size of 77mm whereas the Tamron AF 18-250mm f3.5-6.3 II LD has a 62mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 77mm filters that we recommend you to consider for the Canon 100-400mm f4.5-5.6L IS II USM:
And these are the 62mm filters that we recommend for the Tamron AF 18-250mm f3.5-6.3 II LD:
Lens Mounts
Both the Canon 100-400mm f4.5-5.6L IS II USM and the Tamron AF 18-250mm f3.5-6.3 II LD has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Blackmagic URSA 12K LF, Z CAM E2-F6 II 6K and Z CAM E2-S6 II 6K.
Tamron AF 18-250mm f3.5-6.3 II LD is also available in Nikon F (DX) , Sony Alpha and Pentax KAF mounts.
Focal Range
Canon 100-400mm f4.5-5.6L IS II USM has a focal range of 100-400mm and
4.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of
160 - 640mm.
On the other hand, the 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.
