The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 18-300 F3.5-6.3 DC OS HSM and the Pentax DA 55-300mm F4.0-5.8 ED WR 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. Pentax DA 55-300mm F4.0-5.8 ED WR is the longer of the two lenses at 112mm. The Sigma 18-300 F3.5-6.3 DC OS HSM with a length of 102mm, is 10mm shorter. On the other hand, the Sigma 18-300 F3.5-6.3 DC OS HSM has a larger diameter of 79mm compared to the Pentax DA 55-300mm F4.0-5.8 ED WR's 71mm 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 DA 55-300mm F4.0-5.8 ED WR weighs 466g, 20% (119g) lighter than the Sigma 18-300 F3.5-6.3 DC OS HSM's weight of 585g.
Filter Threads
The Sigma 18-300 F3.5-6.3 DC OS HSM has a filter size of 72mm whereas the Pentax DA 55-300mm F4.0-5.8 ED WR has a 58mm diameter. Larger filters are generally more expensive than the smaller ones given all the other features are equal.
Below are links to the 72mm filters that we recommend you to consider for the Sigma 18-300 F3.5-6.3 DC OS HSM:
And these are the 58mm filters that we recommend for the Pentax DA 55-300mm F4.0-5.8 ED WR:
Lens Mounts
The Sigma 18-300 F3.5-6.3 DC OS HSM has the Pentax KAF3 lens mount whereas the Pentax DA 55-300mm F4.0-5.8 ED WR has the Pentax KAF2 lens mount. Some of the latest released cameras that are compatible with these mounts are Pentax K-3 III Mono, Pentax KF and Pentax K-3 III for the Pentax KAF3 Mount and , and for the Pentax KAF2 Mount.
Sigma 18-300 F3.5-6.3 DC OS HSM is also available in the Canon EF , Nikon F (DX), Sigma SA and Sony Alpha mounts.
Focal Range
Sigma 18-300 F3.5-6.3 DC OS HSM has a focal range of 18-300mm and
16.7X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
27-450mm when used on a APS-C / DX format camera.
On the other hand, the Pentax DA 55-300mm F4.0-5.8 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.
