The type of photography that you are planning to use is an important decision factor. Here we have evaluated the PENTAX28-105mm F3.5-5.6 WR and the Tamron AF 28-300mm f3.5-6.3 XR LD 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. PENTAX28-105mm F3.5-5.6 WR is the longer of the two lenses at 87mm. The Tamron AF 28-300mm f3.5-6.3 XR LD with a length of 84mm, is 3mm shorter. On the other hand, there is no difference between the max diameters of these lenses, both coming at 73mm.
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 28-300mm f3.5-6.3 XR LD weighs 420g, 4% (20g) lighter than the PENTAX28-105mm F3.5-5.6 WR's weight of 440g.
Filter Threads
Both the PENTAX28-105mm F3.5-5.6 WR and the Tamron AF 28-300mm f3.5-6.3 XR LD 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 PENTAX28-105mm F3.5-5.6 WR has the Pentax KAF3 lens mount whereas the Tamron AF 28-300mm f3.5-6.3 XR LD has the Pentax KAF lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF Mount.
Tamron AF 28-300mm f3.5-6.3 XR LD is also available in Canon EF , Nikon F (FX) and Sony Alpha mounts.
Focal Range
PENTAX28-105mm F3.5-5.6 WR has a focal range of 28-105mm and
3.8X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of
42 - 157.5mm.
On the other hand, the Tamron AF 28-300mm f3.5-6.3 XR LD has a focal range of 28-300mm and 10.7X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 42 - 450mm.