Sigma 17-70mm f/2.8 - 4 DC OS HSM

My last lens were Sigma 18-200mm DC OS HSM. I've been use it for a while and I really enjoyed the lens especially its wide focal range feature. However, like many wide-tele superzoom lens, it's prone to produce poor image quality and unsharp image and this lens is not spared from the problem. And don't forget this lens is damn heavy and you need to have super stable hands to be able to stabilize it.

Recently, I've sold the lens and seeking for new lens to try. I'm eyeing for standard zoom lens now and two lenses are really captured my attention. First one is Tamron 17-50mm f/2.8 and another one is Sigma 17-70mm f/2.8-4. To compare:

Brand	Tamron	Sigma
Full Name	Tamron 17-50mm f/2.8 XR Di II LD Aspherical IF	Sigma 17-70 mm f/2.8-4.0 DC Macro OS HSM
Focal Length	17mm-50mm	17mm-70mm
Max Aperture	f/2.8 (fixed)	f/2.8(wide) | f/4.0(tele)
Autofocus	Yes (IF)	Yes (HSM)
Optical Stabilizer	No	Yes
Macro	No	Yes (0.22m)
Price	Lower	Higher by ~37%

Lets start with Tamron first. This one is non VC (vibration compensation). Tamron also got another similar lens with VC but with higher price tag. I really like the fixed maximum aperture on this lens. No matter wide or tele you go on it, the maximum aperture still at f/2.8 and that's really useful in low light condition. It also cheaper by around 37% from the competitor lens. The Sigma on the other hands, offers you extra focal length up to 70mm but at that focal length, the aperture is at f/4.0 ono.

Lets talk about autofocus. The Tamron has old-fashioned internal focus motor and it does produce quite load(but not disturbing for me at least) noise. Sigma however, implemented HSM (Hyper Sonic Motor) that resulting in quick and silent autofocus. In term of focus decisive, both is perform well. Image quality also more or less the same.

For the optical stabiliser, you can opt for similar Tamron lens with VC but I think you may not need it because the maximum aperture is fixed and you can easily snap with higher shutter speed. Just use the rule of thumb. At 50mm, use at least 1/50 shutter speed. I've tried both lens and Tamron really allow us to use this rules and minimizing blurriness. You get Optical Stabiliser with Sigma though. One thing with OS/VS on both lens is, you really need to wait until the stabiliser settle itself before actually snapping a photo. If not, the result can be uglier than not using stabiliser.

To make thing short, I chose the Sigma simply because I want the extra focal length, HSM and macro capability although it's not 1:1 macro. I don't want to have similar focal length as kit lens thats why I'm not very keen with Tamron. If you're on budget constraint though, choose the Tamron. You won't go wrong with it.