The type of photography that you are planning to use is an important decision factor. Here we have evaluated the Sigma 17-70mm F2.8-4 DC OS HSM and the Nikon 18-105mm f3.5-5.6G ED VR 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. Nikon 18-105mm f3.5-5.6G ED VR weighs 420g, 19% (100g) lighter than the Sigma 17-70mm F2.8-4 DC OS HSM's weight of 520g.
Filter Threads
The Sigma 17-70mm F2.8-4 DC OS HSM has a filter size of 72mm whereas the Nikon 18-105mm f3.5-5.6G ED VR has a 67mm 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 17-70mm F2.8-4 DC OS HSM:
And these are the 67mm filters that we recommend for the Nikon 18-105mm f3.5-5.6G ED VR:
Lens Mounts
Both the Sigma 17-70mm F2.8-4 DC OS HSM and the Nikon 18-105mm f3.5-5.6G ED VR has the same Nikon F (DX) lens mount. Some of the latest released cameras that are compatible with the Nikon F (DX) lenses are Nikon D3500, Nikon D7500 and Nikon D5600.
Sigma 17-70mm F2.8-4 DC OS HSM is also available in the Canon EF , Pentax KAF3, Sony Alpha and Sigma SA mounts.
Focal Range
Sigma 17-70mm F2.8-4 DC OS HSM has a focal range of 17-70mm and
4.1X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of
25.5-105mm when used on a APS-C / DX format camera.
On the other hand, the Nikon 18-105mm f3.5-5.6G ED VR has a focal range of 18-105mm and 5.8X zoom ratio which has an effective (full-frame 35mm equivalent) focal range of 27-157.5mm when used on a APS-C / DX format camera.
