Compare lenses

Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR vs Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary

The Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR and the Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary side by side, computed from this guide's catalogue.

Which to pick

Pick the Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR if you want the flexibility of a zoom and coverage of full frame, so it suits the larger-sensor bodies too. Pick the Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary if you want a brighter f/2.8 (0.6 stops more light), for dim light and softer backgrounds; optical stabilisation, which helps most on bodies without it; a design for APS-C, which usually means smaller and lighter; and a fit on more cameras (51 against 20 in this guide).

Still torn? Ask the guide about the Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR and the Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary

Specs side by side

Rows that differ are in full colour; the better value is marked where one is better by any measure.
Spec	Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR	Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary
Maker	Pentax	Sigma
Focal length	28-105mm (zoom)	17-70mm (macro)
Full-frame equivalent	28-105mm	26-105mm on APS-C
Maximum aperture	f/3.5-5.6	f/2.8-4brighter
Made for	Full frame	APS-C
Mounts	Pentax K	Canon EF, Nikon F, Pentax K
Stabilised	no	yesstabilised
Autofocus	yes	yes
Zoom range	3.8×	4.1×
Cameras it fits	20 in this guide	51 in this guidefits more cameras

Focal range, in full-frame terms

Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR: 28-105mm.

Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary: 17-70mm on APS-C, like 26-105mm.

Aperture

Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR: f/3.5 wide open.

Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary: f/2.8 wide open.

Each opening drawn to scale against f/1.4: a smaller f-number lets in more light and blurs the background more.

Field of view

How wide each sees, at each end, on the sensor it was made for.

Cameras they fit

20 cameras in this guide take both, so either works on the same body. In all, the Pentax HD D FA 28-105mm f/3.5-5.6 ED DC WR fits 20 and the Sigma 17-70mm f/2.8-4 DC Macro OS HSM Contemporary 51.