The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 28-300mm f3.5-6.3 VC PZD and the Sigma 18-200mm F3.5-6.3 DC OS HSM C 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 28-300mm f3.5-6.3 VC PZD is the longer of the two lenses at 96mm. The Sigma 18-200mm F3.5-6.3 DC OS HSM C with a length of 86mm, is 10mm shorter. Besides being longer, the Tamron 28-300mm f3.5-6.3 VC PZD also has a larger diameter of 74mm compared to the Sigma 18-200mm F3.5-6.3 DC OS HSM C's 71mm 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. Sigma 18-200mm F3.5-6.3 DC OS HSM C weighs 430g, 20% (110g) lighter than the Tamron 28-300mm f3.5-6.3 VC PZD's weight of 540g.
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
Filter Threads
The Tamron 28-300mm f3.5-6.3 VC PZD has a filter size of 67mm whereas the Sigma 18-200mm F3.5-6.3 DC OS HSM C 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 67mm filters that we recommend you to consider for the Tamron 28-300mm f3.5-6.3 VC PZD:
And these are the 62mm filters that we recommend for the Sigma 18-200mm F3.5-6.3 DC OS HSM C:
Lens Mounts
Both the Tamron 28-300mm f3.5-6.3 VC PZD and the Sigma 18-200mm F3.5-6.3 DC OS HSM C has the same Canon EF lens mount. Some of the latest released cameras that are compatible with the Canon EF lenses are Canon 1D X III, Canon 6D MII and Canon 5D MIV.
Tamron 28-300mm f3.5-6.3 VC PZD is also available in Nikon F (FX) and Sony Alpha mounts.
Sigma 18-200mm F3.5-6.3 DC OS HSM C is also available in Nikon F (DX) , Pentax KAF3, Sony Alpha and Sigma SA mounts.
Focal Range
Tamron 28-300mm f3.5-6.3 VC PZD 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.
On the other hand, the Sigma 18-200mm F3.5-6.3 DC OS HSM C has a focal range of 18-200mm and 11.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 28.8-320mm when used on a APS-C / DX format camera.