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 18-250mm F3.5-6.3 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 18-270mm F3.5-6.3 ED SDM is the longer of the two lenses at 89mm. The Pentax 18-250mm F3.5-6.3 with a length of 86mm is 3mm shorter. Besides being longer, the Pentax 18-270mm F3.5-6.3 ED SDM also has a larger diameter of 76mm compared to Pentax 18-250mm F3.5-6.3's 75mm 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. Pentax 18-270mm F3.5-6.3 ED SDM weighs 453g, which means it is 2g (0%) lighter than the Pentax 18-250mm F3.5-6.3 which has a weight of 455g.
Below you can find the dimension and weight table of the 'SuperZoom Lenses in Pentax KAF Mount for size comparison purposes.
SuperZoom Lenses in Pentax KAF Mount for Size Comparison
Both Pentax 18-270mm F3.5-6.3 ED SDM and Pentax 18-250mm F3.5-6.3 has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax KF, Pentax K-3 III and Pentax KP.
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. Pentax 18-250mm F3.5-6.3 has a focal range of 18-250mm and 13.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-375mm when used on a APS-C / DX format camera.