What 16-70mm at f/4 actually gives you
16-70mm 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 24mm 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 308g (10.9 oz) it sits in the middle for handling: substantial enough to feel planted, light enough not to dominate the kit.
Filters are 55mm — 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 and stabilisation
Autofocus is driven by a DDSSM motor.
Optical stabilisation is built in, which stacks with in-body stabilisation on bodies that have it and does the work alone on bodies that do not.
