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06-11-2010, 04:44 AM   #1
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Upgrade lens

Hi there, I am a Pentax K-x user, I have a 18-55mm kit lens and a Sigma 70-300mm APO lens. I am looking for a upgrade for the 18-55mm lens and currently interested in Sigma 17-70mm f2.8-4.5 DC MACRO Lens but I am not too sure whether it will be a good purchase. Can anyone give me some suggestions?

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Matthew

06-11-2010, 04:47 AM   #2
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There are quite a few reviews of the Sigma 17-70mm macro here: PentaxForums.com Third-Party Lens Review Database - Sigma 17-70mm F2.8-4.5 DC MACRO (AF Lens) Lens Reviews

Hope this helps!

Adam
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06-11-2010, 05:00 AM   #3
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Thanks Adam, I read those so many times and I am wondering can anyone tell me is there much differences between the 18-55mm kit lens and the Sigma 17-70mm, is it worth the money to buy it since I have the 18-55mm lens. BTW, I use my K-x mostly taking pictures of dogs, sky, moving water.

Cheers
Matthew
06-11-2010, 05:09 AM   #4
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If we compare the two lenses, we have the following:

-The Sigma is 1/2 of a stop faster
-The Sigma has a slightly longer zoom range
-The Sigma has a smaller minimum focusing distance

However, there is quite a lot of overlap in the zoom range, obviously. Unless you're looking to upgrade to a quality walkaround lens, I'd stick with the kit lens.


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06-11-2010, 05:30 AM   #5
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Iv'e got both and I find the sigma to be awesome value. Yes it weighs a lot more and I find it has a yellow colour tinge compared to pentax lenses but its much more versatile and IMO is more contrasty and better rendering. However I'd still think about getting a faster prime for either portrait or macro work before upgrading.
06-11-2010, 05:56 AM   #6
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Thanks guys. I am actually looking for a better quality walkaround lens. Any suggestions? I was told that the Sigma 17-70 is pretty good, better than the kit lens I have but after I have done my research, I got confused, not too sure whether I should get the Sigma one or save up more money and get a Pentax 16-50 f2.8.

Cheers
Matt
06-11-2010, 06:10 AM   #7
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The Sigma is pretty hard to beat for the money (I've just purchased one with my to be delivered K7 ) problem is it has been replaced with the 2.8-4.0 OS HSM model so it is a little hard to find. Another well regarded lens is the Tamron 16-50 2.8 if you want a constant aperture. Lots of posts on this subject so do a few searches.
06-11-2010, 06:23 AM   #8
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The Sigma is pretty hard to beat for the money (I've just purchased one with my to be delivered K7 ) problem is it has been replaced with the 2.8-4.0 OS HSM model so it is a little hard to find. Another well regarded lens is the Tamron 16-50 2.8 if you want a constant aperture. Lots of posts on this subject so do a few searches.

06-11-2010, 10:05 AM   #9
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Tubamatt:
After I lot of research I settled on the Sigma. I wanted the Sigma 17-70mm f2.8-4.5 DC MACRO lens also but after over a month of looking I could not find anywhere to purchase it. I even called Sigma to ask who had it in stock, but they said they even had it on backorder. After getting tired of waiting and needing it for an upcoming trip, I ordered the newer version: 17-70mm 2.8-4.0 OS HSM. The newer version has been getting some very good reviews so I went for it. It should arrive next week.
06-11-2010, 10:07 AM   #10
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QuoteOriginally posted by tubamatt Quote
Thanks guys. I am actually looking for a better quality walkaround lens.
Better in what way? The kit lens already has IQ about as good as other zooms when used in the f/8 range s you normally would outdoors. Indoors, though, the maximum f/4 or f/5.6 aperture can be very limiting, and it's not as sharp at those apertures as most faster lens would be, either. It would help if you could describe in more detail exactly what aspect you are unsatisfied with, perhaps with sample images.
06-11-2010, 11:54 AM   #11
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I own the 18-55 WR and the Sigma.

The latter is better in all regards. the kit is excellent in itself, with more contrast and good sharpness. The Sigma has better sharpness, colours, distorsion, and specs (apertures, range, etc).

I own the WR for its WR capabilities. My go-to lens is the Sigma.
06-15-2010, 04:54 AM   #12
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Thanks guys. I decided to stay with the kit lens 18-55mm for a while, because I looked at some sample pictures of the Sigma 17-70mm but they seem to me less sharper than my kit lens so I will save up money for the Pentax 17-70mm or DA* 18-50mm if I can find a good copy. Thanks guys, much appreciated Any more suggestions are welcome, I am looking for a walk around lens with better sharpness than my 18-55mm kit lens.
06-15-2010, 05:15 AM   #13
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You'll find the DA* 16-50 leagues above the kit lens in performance - the only aspect that won't be upgraded will be AF speed (despite the SDM). You'd expect that from a lens 6 times the price.

Nevertheless there are other options, such as the Tamron 17-50, which is just about as good but is not weather sealed or have silent focusing. The Sigma 17-70 will be a step up from the kit lens, but not worlds apart, particularly at the f/8 range. Be weary that the Sigma has variable maximum apertures, with f/4.5 the best you'll get at 70mm. I prefer the Tamron 28-75 at that range given its fixed f/2.8 maximum - and it's clearly a sharp lens.

So lots to consider and choose from, just assess what you're after in the lens and make the comparisons.
06-15-2010, 12:16 PM   #14
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QuoteOriginally posted by tubamatt Quote
Thanks guys. I decided to stay with the kit lens 18-55mm for a while, because I looked at some sample pictures of the Sigma 17-70mm but they seem to me less sharper than my kit lens
The Sigma lens itself is sharper when making an controlled back-to-back comparison. But what you have demonstrated nicely is that the lens itself is very seldom the main determining factor. The shutter speed, focus distance, aperture, steadiness of the photographer's hands or tripod, ISO, camera used, camera settings used, post processing applied, the lighting, the nature of the scene itself - all of these have a *huge* impact on the sharpness of the resulting photo. All else equal, the Sigma *would* produce slightly sharper results, but in the pictures you looked at, all else was *not* equal. And this suggests that if you want sharper pictures, while you *could* buy a sharper lens, simply working on mastering those other elements will often make a bigger difference.

Which is to say, I agree with your decision to stick with the 18-55 for now, but if at some point in the future you've mastered everything else to the point where it does become clear that the lens itself is what is holding you back from further advancement, then don't rule out the Sigma 17-70. On the other hand, there are other lenses that would be better still - but maybe not as much flexibility for the money.
06-15-2010, 02:38 PM   #15
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The best upgrade would be a prime from 28mm to 77mm. Even if that seems out of scope in this discussion, it is well worth mentioning. Then you would have a lens distinctly different from your zooms.
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