The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 18-300mm F3.5-6.3 Di and the Sigma 70-300mm F4-5.6 DG OS for their suitability to various photography scenarios:
Size and Weight Comparison
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 70-300mm F4-5.6 DG OS weighs 610g, 1% (10g) lighter than the Tamron 18-300mm F3.5-6.3 Di's weight of 620g.
Filter Threads
The Tamron 18-300mm F3.5-6.3 Di has a filter size of 67mm whereas the Sigma 70-300mm F4-5.6 DG OS has a 58mm 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 18-300mm F3.5-6.3 Di:
And these are the 58mm filters that we recommend for the Sigma 70-300mm F4-5.6 DG OS:
Lens Mounts
The Tamron 18-300mm F3.5-6.3 Di has the Fujifilm X lens mount whereas the Sigma 70-300mm F4-5.6 DG OS has the Nikon F (FX) lens mount. Some of the latest released cameras that are compatible with these mounts are Fujifilm X-T30 III, Fujifilm X-E5 and Fujifilm X-M5 for the Fujifilm X Mount and Nikon D6, Nikon D780 and Nikon D3500 for the Nikon F (FX) Mount.
Tamron 18-300mm F3.5-6.3 Di is also available in the Sony E mount.
Sigma 70-300mm F4-5.6 DG OS is also available in Canon EF , Pentax KAF3, Sony Alpha and Sigma SA mounts.
Focal Range
Tamron 18-300mm F3.5-6.3 Di has a focal range of 18-300mm and
16.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-450mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 70-300mm F4-5.6 DG OS has a focal range of 70-300mm and 4.3X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 105 - 450mm.
