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 28-80mm f3.5-5.6 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 28-80mm f3.5-5.6 with a length of 70mm, is 17mm shorter. Besides being longer, the PENTAX28-105mm F3.5-5.6 WR also has a larger diameter of 73mm compared to the Tamron AF 28-80mm f3.5-5.6's 72mm 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 28-80mm f3.5-5.6 weighs 237g, 46% (203g) lighter than the PENTAX28-105mm F3.5-5.6 WR's weight of 440g.
Filter Threads
The PENTAX28-105mm F3.5-5.6 WR has a filter size of 62mm whereas the Tamron AF 28-80mm f3.5-5.6 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 62mm filters that we recommend you to consider for the PENTAX28-105mm F3.5-5.6 WR:
And these are the 58mm filters that we recommend for the Tamron AF 28-80mm f3.5-5.6:
Lens Mounts
The PENTAX28-105mm F3.5-5.6 WR has the Pentax KAF3 lens mount whereas the Tamron AF 28-80mm f3.5-5.6 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 28-80mm f3.5-5.6 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 28-80mm f3.5-5.6 has a focal range of 28-80mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides a 35mm (FF) equivalent of 42 - 120mm.