The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-125mm F3.8-5.6 DC HSM and the Pentax 18-135mm F3.5-5.6ED 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 18-125mm F3.8-5.6 DC HSM is the longer of the two lenses at 89mm. The Pentax 18-135mm F3.5-5.6ED with a length of 76mm, is 13mm shorter. Besides being longer, the Sigma 18-125mm F3.8-5.6 DC HSM also has a larger diameter of 74mm compared to the Pentax 18-135mm F3.5-5.6ED's 73mm 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 18-135mm F3.5-5.6ED weighs 405g, 17% (85g) lighter than the Sigma 18-125mm F3.8-5.6 DC HSM's weight of 490g.
Below you can find the dimension and weight table of the SuperZoom Lenses in Pentax KAF3 Mount for size comparison purposes.
Superzoom Lenses in Pentax KAF3 Mount for Size Comparison
Filter Threads
Both the Sigma 18-125mm F3.8-5.6 DC HSM and the Pentax 18-135mm F3.5-5.6ED have the same Filter thread size of 62mm.
Below are links to the 62mm filters that we recommend you to consider for these lenses:
Lens Mounts
Both the Sigma 18-125mm F3.8-5.6 DC HSM and the Pentax 18-135mm F3.5-5.6ED has the same Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF3 lenses are , and .
Sigma 18-125mm F3.8-5.6 DC HSM is also available in the Sony Alpha mount.
Focal Range
Sigma 18-125mm F3.8-5.6 DC HSM has a focal range of 18-125mm and
6.9X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-187.5mm when used on a APS-C / DX format camera.
On the other hand, the Pentax 18-135mm F3.5-5.6ED has a focal range of 18-135mm and 7.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-202.5mm when used on a APS-C / DX format camera.
