The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Pentax D FA 24-70mm F2.8 ED SDM WR and the Tamron AF 28-80mm f3.5-5.6 for their suitability to various photography scenarios:
Size and Weight Comparison
Size of a lens is an important deciding factor when comparing two lenses.Pentax D FA 24-70mm F2.8 ED SDM WR is the longer of the two lenses at 110mm. The Tamron AF 28-80mm f3.5-5.6 with a length of 70mm is 40mm shorter. Besides being longer, the Pentax D FA 24-70mm F2.8 ED SDM WR also has a larger diameter of 89mm compared to Tamron AF 28-80mm f3.5-5.6's 72mm diameter.
Weight of a lens is as important as its external dimensions, especially if you are planning to hand hold your camera and lens combination for longer periods. Tamron AF 28-80mm f3.5-5.6 weighs 237g, 69% (550g) lighter than the Pentax D FA 24-70mm F2.8 ED SDM WR's weight of 787g.
Lens Mounts
Both Pentax D FA 24-70mm F2.8 ED SDM 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 KF, Pentax K-3 III and Pentax K-1 II for the Pentax KAF3 Mount and Pentax KF, Pentax K-3 III and Pentax K-1 II 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
Pentax D FA 24-70mm F2.8 ED SDM WR has a focal range of 24-70mm and 2.9X zoom ratio . When it is mounted on an APS-C sensor camera with 1.5x crop, it provides an 35mm (FF) equivalent of 36 - 105mm.
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 an 35mm (FF) equivalent of 42 - 120mm.