The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 10-20mm F4-5.6 EX DC HSM and the Pentax 10-17mm F3.5-4.5 ED Fisheye 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. Sigma 10-20mm F4-5.6 EX DC HSM is the longer of the two lenses at 81mm. The Pentax 10-17mm F3.5-4.5 ED Fisheye with a length of 72mm, is 9mm shorter. Besides being longer, the Sigma 10-20mm F4-5.6 EX DC HSM also has a larger diameter of 84mm compared to the Pentax 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. Pentax 10-17mm F3.5-4.5 ED Fisheye weighs 320g, 31% (150g) lighter than the Sigma 10-20mm F4-5.6 EX DC HSM's weight of 470g.
Below you can find the dimension and weight table of the Wideangle Zoom Lenses in Pentax KAF Mount for size comparison purposes.
Ultra-Wideangle Lenses in Pentax KAF Mount for Size Comparison
Lens Mounts
Both the Sigma 10-20mm F4-5.6 EX DC HSM and the Pentax 10-17mm F3.5-4.5 ED Fisheye has the same Pentax KAF lens mount. Some of the latest released cameras that are compatible with the Pentax KAF lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Sigma 10-20mm F4-5.6 EX DC HSM is also available in the Canon EF , Four Thirds, Sony Alpha, Sigma SA and Nikon F (DX) mounts.
Focal Range
Sigma 10-20mm F4-5.6 EX DC HSM has a focal range of 10-20mm and
2.0X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
15-30mm when used on a APS-C / DX format camera.
On the other hand, the Pentax 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.
