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04-13-2010, 10:50 AM   #1
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Sigma 17-50mm f/2.8. A viable alternative as a standard zoom?

I have used the kit lens DA 18-55mm as a standard zoom on my first DSLR K100D as a beginner.
It was fine; no big problems.

After feeling better with my technique and upgrading to K10D, I moved to Sigma 17-70mm f/2.8-4.5mm.
I loved that lens; nice range, fairly good image quality, ability to close focus and a fine build. I acquired many other lenses in the meantime (the lovely DA 40mm Ltd, the beautiful FA 77mm Ltd and the problematic DA* 50-135mm). Then, Sigma started to feel a bit below my expectations...

Then, I had Sigma 24-60mm f/2.8 as a standard, fixed wide aperture zoom (I had the very functional Sigma 10-20mm already to go really wide). However, its wide open performance was not up to my expectations (as I was spoiled by the DA 40mm Ltd). These were all on K20D; my latest addiction!

Now I look at Pentax offerings:
DA 17-70mm f/4?
Why f/4? I am ready to offer more for a good f/2.8 (I expect this as my last purchase, a cure for LBA).

DA* 16-50mm f/2.8?
Definitely no! I have a failed (after warranty) 50-135mm with a stupid SDM problem. It is now fixed but stands in a drawer somewhere; I seem to have lost confidence in it.
Also, as a regular reader of this forum, I am well aware of the reported problems with this particular lens. Please do not tell me about the warranty; I am not living in the US!

Now comes the recently (February 21st) announced Sigma offering: 17-50mm f/2.8 with ultrasonic motor and shake reduction (Sigma has different terms for those). It is an EX series lens. I hear that C* and N* variants will be on the market within a month or so. Pentax and Sony variants will be available afterwards. The suggested retail price will probably be close to USD 900 (I may be seriously wrong about the price as this info is quite indirect).

I do not have a Tamron 17-50mm but I have read quite positive remarks on it. It, however, lacks the "sweet" AF motor and it does not have image stabilization.

Thank you for following me until here : )
Do you think I should be buying this Sigma as my last standard zoom?

Last edited by bc_the_path; 04-13-2010 at 01:11 PM.
04-13-2010, 11:13 AM   #2
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Actually there is a stabilized Tamron 17-50/2.8 but it's said to be worse than the non-stabilized one. But stabilized lenses are not that much better than sensor stabilized anyway. The AF motor shall be your deciding point then...
04-13-2010, 12:44 PM   #3
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You do not need SR if you have a k10d. It is built in to the body. The Tamron 17-50 is a great lens and I am not sure if any kind of hypersonic motor is that important. I suppose that's up to your own needs (I personally think weather sealing is more important than any other kind of quieter motor, as long as af is reasonably fast). I am not trying to start a long argument on the merits (or problems) with sdm. There is a lot of people who have had hsm fail on their sigmas (and I know there is a better warranty for them than Pentax offers) but the DA*16-50 has amazing IQ...........
04-13-2010, 01:20 PM   #4
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This lens just came out and is untested by pretty much everyone. You might be interested also in the new Sigma 17-70mm OS lens, which is incredibly sharp, or the older Sigma 18-50mm (now with an OS version, actually). I can't give any advice on the lens you have though, depending on whether or not the OS is really important to you (also depends on what Pentax you have).

04-13-2010, 01:27 PM   #5
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Original Poster
atiratha, ari and jct us101

Thank you for your considerate opinions.
My standard zoom has to have autofocus (I would love to be able have a Quick Shift manual focus as well).
The above-mentioned Pentax zoom is out of question because (a) it has SDM (and SDM-only on K20D), (b) I can not return the lens, if required, as easily as most other members of this forum. Not to mention the fact that its price here will be about two times the suggested retail price.

I am really happy with the sensor based shake reduction on my K20D. Still, the ability to see a "stabilized image on the viewfinder" sounds nice if I do not have to pay too much for this. (I know Sigma suggests using just one of the SR mechanisms).

Certainly, neither ultrasonic AF nor SR is essential; I am looking for a near prime IQ most. The DA* 50-135 comes closest to this definition, image quality wise (as a tele-zoom, of course). Unfortunately, I can not make myself come into terms with its AF implementation.
04-13-2010, 01:30 PM   #6
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If you want near prime IQ, then go with the older Sigma 17-70mm. Seriously, that is the sharpest lens that I have ever used.

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