Hi, I'll replying to your question

1) I'm not sure about the cheapest price for the Sigma 17-70mm because I'm not from KL but you can search for the sigma official distributor (can't remember the name of the company sry)

2) It is compatible with A33. The incompatibility issues are with old lenses which does not recognize the A33. Make sure you check when you buy it. If you have no choice then just send it back to Sigma for rechipping (should be free of charge).  The new lenses from Sigma should have no problems whatsoever.

3) There is an older version of the lens (Its cheaper too) which has no OS but it does not have the HSM so there is no silent focus. If no HSM then you're better off getting something else such as the Tammy 17-50mm as the sound generated during focusing will annoy the hell out of you during video taking.

Hope this helps to clarify a bit, correct me if I'm wrong =)

deathbringer, i wonder why u want that sigma? not other brand such as tamron for example...

how does the 17-70 replace your kit lens? the f2.8 is not constant wei.

get a constant.. haha.. u ll like it

sometimes f4 is just nt enuf

ya, it's cheaper...but it's aps-c only... gud if u din plan to upgrade to FF anytime soon

Pros and cons of the Sigma 17-70mm OS HSM

Pros:

1.HSM - silent focus, really useful in capturing video as AF noise will not be recorded as it is not present.

2.Very short MFD (Minimum focus distance) - 22cm. So you could practically take close-ups of pics and be creative. (p.s. Its a really good camwhore lens LOL!) Tamron 17-50mm has a MFD of 27mm and the Carl Zeiss 1680z has MFD of 35cm.
Albnok also refered to it as Sigma 17-70mm OS HSM "Macro" due to the short MFD and the long zoom which enables amazing close ups!

3.Built in OS - According to some reviews by people, the built in OS in the lens offers 1-2 stop extra image stabilization compared to the SSS in the Alpha bodies. It also offers stabilization in the view finder 

Cons:

1.No constant aperature

2.Price (if compared to the Tamron 17-50mm)

i didn't claim anything la. but some reports and reader comments shows that a55 is slightly cleaner at high iso(iso 3200) than the a33. about half a stop better.

my point is, and what i believe and read from is, a33 and a55 have different sensors. so by saying that a55 is 'only 2 megapixels better & got gps compared to the a33' is really undervaluing the a55. 

and yes, i could be totally wrong. 

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Added on January 3, 2011, 1:27 pm

my not so concrete source

http://www.dyxum.com/dforum/is-there-a-big...topic70941.html

optically wise its very good and sharp. but the focusing speed is loud and slow. 

bokeh is not bad too. 

one of my recent shot with the lens:


Girl with DSLR by zstan, on Flickr

It's my sharpest lens to date, which tells a lot for a 2nd hand lens. I've been using it as my primary lens if I want a really sharp picture without bokeh. My lens of choice during PC fair girls stalking

http://wakarimasenlol.com/2010/12/07/kuala...-show-2010/5251

are you in need of cash? if not you never know when you might use it again...in case you buy another body then dun need get another lens.....   

why do you need tele lens for travel? I use mostly UWA and tamron 17-50 only 

deathbringer: It sounds like gear stripping if:

- mount lens on camera with lens AF/MF switch set to AF (if it is the SAM version) and camera set to AF
- the lens immediately rotates to infinity, and starts vibrating madly

It could be that either camera or lens was set to MF when at the shop.

Note that when using the Sony 55-200mm F4-5.6 DT SAM (II) you need to turn the switch on the lens to MF in order to manual focus - if not, you will be working against the SAM motor.

deathbringer:

What is your camera, and does your 55-200mm have an AF/MF switch on the lens?

The A550 onwards did not seem to drive a SAM lens to infinity automatically - a departure from previous convention where all Alphas would reset the lens to infinity upon mounting the lens.