The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax DA 50-135mm F2.8 ED and the Pentax 18-55mm F3.5-5.6 AL 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 Pentax 18-55mm F3.5-5.6 AL with a length of 68mm, is 68mm shorter. Besides being longer, the Pentax DA 50-135mm F2.8 ED also has a larger diameter of 77mm compared to the Pentax 18-55mm F3.5-5.6 AL's 68mm 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 18-55mm F3.5-5.6 AL weighs 225g, 67% (460g) lighter than the Pentax DA 50-135mm F2.8 ED's weight of 685g.
Filter Threads
The Pentax DA 50-135mm F2.8 ED has a filter size of 67mm whereas the Pentax 18-55mm F3.5-5.6 AL has a 52mm 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 Pentax DA 50-135mm F2.8 ED:
And these are the 52mm filters that we recommend for the Pentax 18-55mm F3.5-5.6 AL:
Lens Mounts
The Pentax DA 50-135mm F2.8 ED has the Pentax KAF2 lens mount whereas the Pentax 18-55mm F3.5-5.6 AL has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are , and for the Pentax KAF2 Mount and Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Focal Range
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.
On the other hand, the Pentax 18-55mm F3.5-5.6 AL has a focal range of 18-55mm and 3.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-82.5mm when used on a APS-C / DX format camera.