The type of photography that you are planning to use is an important decision factor. Here we have evaluated the PENTAX 55-300mm F4.5-6.3 ED WR and the Sigma 18-250mm F3.5-6.3 DC OS HSM for their suitability to various photography scenarios:
Size and Weight Comparison
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. Sigma 18-250mm F3.5-6.3 DC OS HSM weighs 470g, 0% (1g) lighter than the PENTAX 55-300mm F4.5-6.3 ED WR's weight of 471g.
Below you can find the dimension and weight table of the Telephoto Zoom Lenses in Pentax KAF3 Mount for size comparison purposes.
Super Telephoto Lenses in Pentax KAF3 Mount for Size Comparison
Filter Threads
The PENTAX 55-300mm F4.5-6.3 ED WR has a filter size of 58mm whereas the Sigma 18-250mm F3.5-6.3 DC OS HSM has a 72mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 58mm filters that we recommend you to consider for the PENTAX 55-300mm F4.5-6.3 ED WR:
And these are the 72mm filters that we recommend for the Sigma 18-250mm F3.5-6.3 DC OS HSM:
Lens Mounts
Both the PENTAX 55-300mm F4.5-6.3 ED WR and the Sigma 18-250mm F3.5-6.3 DC OS HSM has the same Pentax KAF3 lens mount. Some of the latest released cameras that are compatible with the Pentax KAF3 lenses are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III.
Sigma 18-250mm F3.5-6.3 DC OS HSM is also available in Canon EF , Nikon F (DX), Sony Alpha, Sigma SA, Canon EF, Nikon F (DX), Pentax KAF3, Sony Alpha and Sigma SA mounts.
Focal Range
PENTAX 55-300mm F4.5-6.3 ED WR has a focal range of 55-300mm and
5.5X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
82.5-450mm when used on a APS-C / DX format camera.
On the other hand, the Sigma 18-250mm F3.5-6.3 DC OS HSM 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.
