The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron 70-200mm f2.8 LD and the Sigma 70-300mm F4-5.6 DG 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 70-200mm f2.8 LD is the longer of the two lenses at 194mm. The Sigma 70-300mm F4-5.6 DG with a length of 122mm, is 72mm shorter. Besides being longer, the Tamron 70-200mm f2.8 LD also has a larger diameter of 90mm compared to the Sigma 70-300mm F4-5.6 DG's 77mm 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 70-300mm F4-5.6 DG weighs 550g, 58% (780g) lighter than the Tamron 70-200mm f2.8 LD's weight of 1330g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Pentax KAF Mount for size comparison purposes.
Telephoto Lenses in Pentax KAF Mount for Size Comparison
Filter Threads
The Tamron 70-200mm f2.8 LD has a filter size of 77mm whereas the Sigma 70-300mm F4-5.6 DG 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 77mm filters that we recommend you to consider for the Tamron 70-200mm f2.8 LD:
And these are the 58mm filters that we recommend for the Sigma 70-300mm F4-5.6 DG:
Lens Mounts
Both the Tamron 70-200mm f2.8 LD and the Sigma 70-300mm F4-5.6 DG has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III.
Tamron 70-200mm f2.8 LD is also available in Canon EF , Nikon F (FX) and Sony Alpha mounts.
Sigma 70-300mm F4-5.6 DG is also available in Canon EF , Nikon F (FX), Pentax KAF, Sony Alpha, Sigma SA, Canon EF, Nikon F (FX), Sony Alpha and Sigma SA mounts.
Focal Range
Tamron 70-200mm f2.8 LD has a focal range of 70-200mm and
2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
105 - 300mm.
On the other hand, the Sigma 70-300mm F4-5.6 DG 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.