The type of photography that you are planning to use is an important decision factor. Here we have evaluated the HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye and the HD Pentax-DA 11-18mm F2.8 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. HD Pentax-DA 11-18mm F2.8 is the longer of the two lenses at 100mm. The HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye with a length of 70mm, is 30mm shorter. Besides being longer, the HD Pentax-DA 11-18mm F2.8 also has a larger diameter of 90mm compared to the HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye's 68mm 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. HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye weighs 317g, which means it is 387g (54%) lighter than the HD Pentax-DA 11-18mm F2.8 which has a weight of 704g.
Lens Mounts
The HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye has the Pentax KAF lens mount whereas the HD Pentax-DA 11-18mm F2.8 has the Pentax KAF3 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 KAF Mount and Pentax K-3 III Monochrome, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount.
Focal Range
HD Pentax-DA 10-17mm F3.5-4.5 ED fisheye has a focal range of 10-17mm and
1.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
15-25.5mm when used on a APS-C / DX format camera.
On the other hand, the HD Pentax-DA 11-18mm F2.8 has a focal range of 11-18mm and 1.6X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 16.5-27mm when used on a APS-C / DX format camera.