The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 20-200mm F3.5-6.3 and the Tamron 18-200mm f3.5-6.3 III VC 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 20-200mm F3.5-6.3 is the longer of the two lenses at 118mm. The Tamron 18-200mm f3.5-6.3 III VC with a length of 97mm, is 21mm shorter. Besides being longer, the Sigma 20-200mm F3.5-6.3 also has a larger diameter of 77mm compared to the Tamron 18-200mm f3.5-6.3 III VC's 68mm 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 18-200mm f3.5-6.3 III VC weighs 460g, 14% (80g) lighter than the Sigma 20-200mm F3.5-6.3's weight of 540g.
Below you can find the dimension and weight table of the SuperZoom Lenses in Sony E Mount for size comparison purposes.
Superzoom Lenses in Sony E Mount for Size Comparison
Filter Threads
The Sigma 20-200mm F3.5-6.3 has a filter size of 72mm whereas the Tamron 18-200mm f3.5-6.3 III VC 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 72mm filters that we recommend you to consider for the Sigma 20-200mm F3.5-6.3:
And these are the 62mm filters that we recommend for the Tamron 18-200mm f3.5-6.3 III VC:
Lens Mounts
Both the Sigma 20-200mm F3.5-6.3 and the Tamron 18-200mm f3.5-6.3 III VC has the same Sony E lens mount. Some of the latest released cameras that are compatible with the Sony E lenses are Sony FX5, Sony A7R VI and Sony A7 V.
Sigma 20-200mm F3.5-6.3 is also available in the Leica L mount.
Focal Range
Sigma 20-200mm F3.5-6.3 has a focal range of 20-200mm and
10.0X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
30 - 300mm.
On the other hand, the Tamron 18-200mm f3.5-6.3 III VC has a focal range of 18-200mm and 11.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-300mm when used on a APS-C / DX format camera.
