The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 300-800mm F5.6 EX DG HSM and the Sigma 120-300mm F2.8 EX DG HSM 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 300-800mm F5.6 EX DG HSM is the longer of the two lenses at 544mm. The Sigma 120-300mm F2.8 EX DG HSM with a length of 271mm, is 273mm shorter. Besides being longer, the Sigma 300-800mm F5.6 EX DG HSM also has a larger diameter of 157mm compared to the Sigma 120-300mm F2.8 EX DG HSM's 113mm 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 120-300mm F2.8 EX DG HSM weighs 2600g, 55% (3280g) lighter than the Sigma 300-800mm F5.6 EX DG HSM's weight of 5880g.
Filter Threads
The Sigma 300-800mm F5.6 EX DG HSM has a filter size of 46mm whereas the Sigma 120-300mm F2.8 EX DG HSM has a 105mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 46mm filters that we recommend you to consider for the Sigma 300-800mm F5.6 EX DG HSM:
And these are the 105mm filters that we recommend for the Sigma 120-300mm F2.8 EX DG HSM:
Lens Mounts
Both the Sigma 300-800mm F5.6 EX DG HSM and the Sigma 120-300mm F2.8 EX DG HSM has the same Sigma SA lens mount. Some of the latest released cameras that are compatible with the Sigma SA lenses are Sigma Quattro, Sigma Quattro H and Sigma SD1 Merrill.
Sigma 300-800mm F5.6 EX DG HSM is also available in Canon EF and Nikon F (FX) mounts.
Sigma 120-300mm F2.8 EX DG HSM is also available in Canon EF and Nikon F (FX) mounts.
Focal Range
Sigma 300-800mm F5.6 EX DG HSM has a focal range of 300-800mm and
2.7X zoom ratio .
On the other hand, the Sigma 120-300mm F2.8 EX DG HSM has a focal range of 120-300mm and 2.5X zoom ratio .