What 18-120mm at f/4 actually gives you
18-120mm is wide enough to take in interiors, landscapes and architecture without the pronounced edge stretching of an ultra-wide. On the APS-C bodies it covers, it frames like 27mm would on full-frame.
f/4 is a moderate maximum aperture. There is less low-light headroom and less background blur than an f/2.8 lens gives, which is generally the trade for lower weight and cost.
Size and filters
At 460g (1.01 lb) it sits in the middle for handling: substantial enough to feel planted, light enough not to dominate the kit.
Filters are 72mm — worth checking against what you already own, since polarisers and ND filters at this size are reusable across any other lens sharing the thread.
Autofocus, stabilisation and weather sealing
Autofocus is driven by a Linear motor.
There is no optical stabilisation in the lens, so handheld steadiness depends on the body having IBIS, or on keeping the shutter speed up.
The barrel is weather-sealed, so rain and dust are a manageable risk rather than a reason to pack up.
