The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Panasonic S 20-60mm F3.5-5.6 and the Pentax DA 18-50mm F4.5-5.6 DC WR RE 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. Panasonic S 20-60mm F3.5-5.6 is the longer of the two lenses at 87mm. The Pentax DA 18-50mm F4.5-5.6 DC WR RE with a length of 71mm, is 16mm shorter. Besides being longer, the Panasonic S 20-60mm F3.5-5.6 also has a larger diameter of 77mm compared to the Pentax DA 18-50mm F4.5-5.6 DC WR RE's 41mm 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 18-50mm F4.5-5.6 DC WR RE weighs 158g, 54% (192g) lighter than the Panasonic S 20-60mm F3.5-5.6's weight of 350g.
Filter Threads
The Panasonic S 20-60mm F3.5-5.6 has a filter size of 67mm whereas the Pentax DA 18-50mm F4.5-5.6 DC WR RE 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 67mm filters that we recommend you to consider for the Panasonic S 20-60mm F3.5-5.6:
And these are the 58mm filters that we recommend for the Pentax DA 18-50mm F4.5-5.6 DC WR RE:
Lens Mounts
The Panasonic S 20-60mm F3.5-5.6 has the Leica L lens mount whereas the Pentax DA 18-50mm F4.5-5.6 DC WR RE has the Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with these mounts are Leica SL3, Panasonic S5 II and Panasonic S5 II X for the Leica L Mount and Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Focal Range
Panasonic S 20-60mm F3.5-5.6 has a focal range of 20-60mm and
3.0X zoom ratio .
On the other hand, the Pentax DA 18-50mm F4.5-5.6 DC WR RE has a focal range of 18-50mm and 2.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-75mm when used on a APS-C / DX format camera.