The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 70-200mm F2.8 GM II 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. Sony FE 70-200mm F2.8 GM II is the longer of the two lenses at 200mm. The Pentax DA 50-135mm F2.8 ED with a length of 136mm, is 64mm shorter. Besides being longer, the Sony FE 70-200mm F2.8 GM II also has a larger diameter of 88mm compared to the Pentax DA 50-135mm F2.8 ED'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. Pentax DA 50-135mm F2.8 ED weighs 685g, 34% (360g) lighter than the Sony FE 70-200mm F2.8 GM II's weight of 1045g.
Filter Threads
The Sony FE 70-200mm F2.8 GM II has a filter size of 77mm 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 77mm filters that we recommend you to consider for the Sony FE 70-200mm F2.8 GM II:
And these are the 67mm filters that we recommend for the Pentax DA 50-135mm F2.8 ED:
Lens Mounts
The Sony FE 70-200mm F2.8 GM II has the Sony E 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 Sony FX5, Sony A7R VI and Sony A7 V for the Sony E Mount and , and for the Pentax KAF2 Mount.
Focal Range
Sony FE 70-200mm F2.8 GM II 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 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.
