The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax 18-270mm F3.5-6.3 ED SDM and the Pentax 18-135mm F3.5-5.6ED 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 18-270mm F3.5-6.3 ED SDM is the longer of the two lenses at 89mm. The Pentax 18-135mm F3.5-5.6ED with a length of 76mm, is 13mm shorter. Besides being longer, the Pentax 18-270mm F3.5-6.3 ED SDM also has a larger diameter of 76mm compared to the Pentax 18-135mm F3.5-5.6ED's 73mm 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 18-135mm F3.5-5.6ED weighs 405g, 10% (48g) lighter than the Pentax 18-270mm F3.5-6.3 ED SDM's weight of 453g.
Filter Threads
Both the Pentax 18-270mm F3.5-6.3 ED SDM and the Pentax 18-135mm F3.5-5.6ED have the same Filter thread size of 62mm.
Below are links to the 62mm filters that we recommend you to consider for these lenses:
Lens Mounts
The Pentax 18-270mm F3.5-6.3 ED SDM has the Pentax KAF lens mount whereas the Pentax 18-135mm F3.5-5.6ED has the Pentax KAF3 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 KAF3 Mount.
Focal Range
Pentax 18-270mm F3.5-6.3 ED SDM has a focal range of 18-270mm and
15.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-405mm when used on a APS-C / DX format camera.
On the other hand, the Pentax 18-135mm F3.5-5.6ED has a focal range of 18-135mm and 7.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-202.5mm when used on a APS-C / DX format camera.
