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 300mm F4.0 ED 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 300mm F4.0 ED is the longer of the two lenses at 184mm. The Sigma 18-300 F3.5-6.3 DC OS HSM with a length of 102mm, is 82mm shorter. Besides being longer, the Pentax DA 300mm F4.0 ED also has a larger diameter of 83mm compared to the Sigma 18-300 F3.5-6.3 DC OS HSM's 79mm 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. Sigma 18-300 F3.5-6.3 DC OS HSM weighs 585g, which means it is 485g (45%) lighter than the Pentax DA 300mm F4.0 ED which has a weight of 1070g.
Filter Threads
The Sigma 18-300 F3.5-6.3 DC OS HSM has a filter size of 72mm whereas the Pentax DA 300mm F4.0 ED has a 77mm 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 77mm filters that we recommend for the Pentax DA 300mm F4.0 ED:
Lens Mounts
The Sigma 18-300 F3.5-6.3 DC OS HSM has the Pentax KAF3 lens mount whereas the Pentax DA 300mm F4.0 ED 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 300mm F4.0 ED is a prime lens with fixed focal lenght of 300mm which has an effective (full-frame 35mm equivalent) focal range of 450mm when used on a APS-C / DX format camera.
