The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sony FE 28-70mm F3.5-5.6 II and the Pentax 15mm F4 ED AL L 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 28-70mm F3.5-5.6 II is the longer of the two lenses at 83mm. The Pentax 15mm F4 ED AL L with a length of 40mm, is 43mm shorter. Besides being longer, the Sony FE 28-70mm F3.5-5.6 II also has a larger diameter of 73mm compared to the Pentax 15mm F4 ED AL L's 63mm 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 15mm F4 ED AL L weighs 189g, 35% (106g) lighter than the Sony FE 28-70mm F3.5-5.6 II's weight of 295g.
Filter Threads
The Sony FE 28-70mm F3.5-5.6 II has a filter size of 55mm whereas the Pentax 15mm F4 ED AL L has a 49mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 55mm filters that we recommend you to consider for the Sony FE 28-70mm F3.5-5.6 II:
And these are the 49mm filters that we recommend for the Pentax 15mm F4 ED AL L:
Lens Mounts
The Sony FE 28-70mm F3.5-5.6 II has the Sony E lens mount whereas the Pentax 15mm F4 ED AL L has the Pentax KAF 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 Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Focal Range
Sony FE 28-70mm F3.5-5.6 II has a focal range of 28-70mm and
2.5X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
42 - 105mm.
On the other hand, the Pentax 15mm F4 ED AL L is a prime lens with fixed focal lenght of 15mm which has an effective (full-frame 35mm equivalent) focal range of 22.5mm when used on a APS-C / DX format camera.
