What 100-400mm at f/4.5 actually gives you
100-400mm is the classic portrait range — long enough to compress features flatteringly without forcing you across the room.
f/4.5 is a slow maximum aperture, so this leans on good light or on a stabilised body.
Size and weight
At 1840g (4.06 lb) this is a lens you plan around — it wants a larger body to balance against, and a tripod collar or monopod for extended use. A tripod collar is included, which moves the mounting point to the lens's centre of mass rather than hanging the weight off the camera's tripod thread.
Autofocus, stabilisation and weather sealing
Autofocus is driven by an XD Linear Motor 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.
The barrel is weather-sealed, so rain and dust are a manageable risk rather than a reason to pack up.
