Compare lenses

Pentax smc DA 17-70mm f/4 AL [IF] SDM vs Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF)

The Pentax smc DA 17-70mm f/4 AL [IF] SDM and the Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF) side by side, computed from this guide's catalogue.

Which to pick

Pick the Pentax smc DA 17-70mm f/4 AL [IF] SDM if you want more reach (to 105mm equivalent). Pick the Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF) if you want a brighter f/2.8 (1.0 stops more light), for dim light and softer backgrounds and a fit on more cameras (51 against 20 in this guide).

Still torn? Ask the guide about the Pentax smc DA 17-70mm f/4 AL [IF] SDM and the Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF)

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 smc DA 17-70mm f/4 AL [IF] SDM	Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF)
Maker	Pentax	Tamron
Focal length	17-70mm (zoom)	17-50mm (zoom)
Full-frame equivalent	26-105mm on APS-C	26-75mm on APS-C
Maximum aperture	f/4	f/2.8brighter
Made for	APS-C	APS-C
Mounts	Pentax K	Canon EF, Nikon F, Pentax K
Stabilised	no	no
Autofocus	yes	yes
Zoom range	4.1×more range	2.9×
Cameras it fits	20 in this guide	51 in this guidefits more cameras

Focal range, in full-frame terms

Pentax smc DA 17-70mm f/4 AL [IF] SDM: 17-70mm on APS-C, like 26-105mm.

Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF): 17-50mm on APS-C, like 26-75mm.

Aperture

Pentax smc DA 17-70mm f/4 AL [IF] SDM: f/4 wide open.

Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF): 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 smc DA 17-70mm f/4 AL [IF] SDM fits 20 and the Tamron SP AF 17-50mm f/2.8 XR Di II LD Aspherical (IF) 51.