The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 70-300mm F4-5.6 DG and the Pentax DA 50-135mm F2.8 ED 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. Pentax DA 50-135mm F2.8 ED is the longer of the two lenses at 136mm. The Sigma 70-300mm F4-5.6 DG with a length of 122mm, is 14mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 77mm.
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, which means it is 135g (19%) lighter than the Pentax DA 50-135mm F2.8 ED which has a weight of 685g.
Filter Threads
The Sigma 70-300mm F4-5.6 DG has a filter size of 58mm whereas the Pentax DA 50-135mm F2.8 ED has a 67mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 58mm filters that we recommend you to consider for the Sigma 70-300mm F4-5.6 DG:
And these are the 67mm filters that we recommend for the Pentax DA 50-135mm F2.8 ED:
Lens Mounts
The Sigma 70-300mm F4-5.6 DG has the Pentax KAF lens mount whereas the Pentax DA 50-135mm F2.8 ED has the Pentax KAF2 lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount and , and for the Pentax KAF2 Mount.
Sigma 70-300mm F4-5.6 DG is also available in the Canon EF , Nikon F (FX), Sony Alpha, Sigma SA, Canon EF, Nikon F (FX), Pentax KAF, Sony Alpha and Sigma SA mounts.
Focal Range
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.
On the other hand, the Pentax DA 50-135mm F2.8 ED has a focal range of 50-135mm and 2.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 75-202.5mm when used on a APS-C / DX format camera.
