The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Tamron AF 28-200mm f3.8-5.6 XR 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 18-135mm F3.5-5.6ED is the longer of the two lenses at 76mm. The Tamron AF 28-200mm f3.8-5.6 XR with a length of 75mm, is 1mm shorter. Besides being longer, the Pentax 18-135mm F3.5-5.6ED also has a larger diameter of 73mm compared to the Tamron AF 28-200mm f3.8-5.6 XR's 71mm 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. Tamron AF 28-200mm f3.8-5.6 XR weighs 354g, which means it is 51g (12%) lighter than the Pentax 18-135mm F3.5-5.6ED which has a weight of 405g.
Filter Threads
Both the Tamron AF 28-200mm f3.8-5.6 XR 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 Tamron AF 28-200mm f3.8-5.6 XR 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.
Tamron AF 28-200mm f3.8-5.6 XR is also available in the Canon EF , Nikon F (FX) and Sony Alpha mounts.
Focal Range
Tamron AF 28-200mm f3.8-5.6 XR has a focal range of 28-200mm and
7.1X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
42 - 300mm.
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.
