The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 18-400mm F3.5-6.3 VC and the Tamron AF 28-300mm f3.5-6.3 XR VC 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. Tamron 18-400mm F3.5-6.3 VC is the longer of the two lenses at 124mm. The Tamron AF 28-300mm f3.5-6.3 XR VC LD with a length of 78mm, is 46mm shorter. On the other hand, the Tamron AF 28-300mm f3.5-6.3 XR VC LD has a larger diameter of 99mm compared to the Tamron 18-400mm F3.5-6.3 VC's 79mm 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 28-300mm f3.5-6.3 XR VC LD weighs 555g, 21% (155g) lighter than the Tamron 18-400mm F3.5-6.3 VC's weight of 710g.
Filter Threads
The Tamron 18-400mm F3.5-6.3 VC has a filter size of 72mm whereas the Tamron AF 28-300mm f3.5-6.3 XR VC LD has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Tamron 18-400mm F3.5-6.3 VC:
And these are the 67mm filters that we recommend for the Tamron AF 28-300mm f3.5-6.3 XR VC LD:
Lens Mounts
The Tamron 18-400mm F3.5-6.3 VC has the Canon EF-S lens mount whereas the Tamron AF 28-300mm f3.5-6.3 XR VC LD has the Canon EF lens mount. Some of the latest released cameras that are compatible with these mounts are Canon T8i, Canon 90D and Canon SL3 for the Canon EF-S Mount and Canon 1D X III, Canon 6D MII and Canon 5D MIV for the Canon EF Mount.
Tamron 18-400mm F3.5-6.3 VC is also available in Nikon F (DX) mount.
Tamron AF 28-300mm f3.5-6.3 XR VC LD is also available in Nikon F (FX) mount.
Focal Range
Tamron 18-400mm F3.5-6.3 VC has a focal range of 18-400mm and
22.2X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
28.8-640mm when used on a APS-C / DX format camera.
On the other hand, the Tamron AF 28-300mm f3.5-6.3 XR VC LD has a focal range of 28-300mm and 10.7X zoom ratio . When it is mounted on an APS-C sensor camera with 1.6x crop, it provides a 35mm (FF) equivalent of 44.8 - 480mm.