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I have a Canon 600D with a kit 18-55 f3.5-5.6 IS II lens. Now I want to upgrade it with my not very loose budget.

Three main things I want to improve with a new lens are:

  1. larger aperture
  2. better build quality (especially more precise manual focusing)
  3. larger zoom

After studying a lot of reviews I have now 4 candidates, but I can't make a decision which one is really better for me. The lenses are:

  1. Sigma 17-70mm f/2.8-4 DC Macro OS HSM
  2. Canon EF-S 18-200mm f/3.5-5.6 IS
  3. Sigma 18-250mm f/3.5-6.3 DC OS HSM
  4. Tamron 18-270mm f/3.5-6.3 Di II VC PZD

Probably the main thing that bothers me is how does the image quality compare between these lenses in 18-70 range. Whether does Sigma 17-70mm have better image quality than other 3 super-zooms? Of course the fact that it has large aperture is very positive for me but the change from maximum zoom of 55 to 70 doesn't look very impressive compared to 250 or 270 mm.

Also I've seen some very positive reviews about image quality of Canon EF-S 15-85mm f/3.5-5.6 IS USM. It is a bit more expensive and has small aperture. Does somebody know if is it really that much better than Sigma 17-70?

I am also curious about the accuracy of autofocus and effectiveness of image stabilisation (vibration control) between different brands.

If somebody has some experience with any of these lenses or, even better, more than one of these, I would be very grateful to see the comments.

Update: Does somebody know anything about Tamron SP AF 17-50mm F/2.8 XR Di II VC? What is image quality, build quality, especially compared to Sigma 17-70 f/2.8-4?

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2 Answers 2

The Sigma 17-70mm F/2.8-4 is actually a very good performer. Compared to it, the other lenses you are looking produce much lower image quality. This should not be surprising as large zoom ratios require compromises in design and they also have very dim apertures at the long end.

The best way to increase zoom is to get a complimentary lens but given the lens you already have, I understand the urgency to replace it. The usual upgrade is the 17-55mm F/2.8 which is extremely sharp, brighter and considerably more expensive but it is worth every penny. If you can afford it, I would start here and later get a longer lens.

The Canon EF-S 15-85mm is good too, almost as sharp as the Sigma 17-70mm but it vignettes severely near wide-angle and until about 24mm, you need to stop it down to F/8 to avoid disturbing shading at image corners. Both these lens show a moderate amount of distortion.

Expect faster autofocus with the Canon USM lenses than with the Sigma. I have no idea how the image stabilization compares.

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Thanks for the contribution. I am also thinking more about shorte zoom range and larger aperture. Yes, Canon 17-55mm F/2.8 should be awesome, but the price is really high. –  BartoNaz Jan 5 '13 at 0:41
    
I love my 17-55 F2.8. It was about $1100, but its my main daily lens. I totally love it. I also picked up a 55-250 for under $100 on craigslist, which covers the long lengths. So far, I'm happy with the inexpensive 55-250, but of course I lust for something much faster. –  Pat Farrell Jan 5 '13 at 7:01

As Itai has already suggested, the large zoom range lenses suffer from poor IQ and narrower apertures than the smaller zooms. For that reason, I would also suggest to go with a combination of two lenses if you want to have a long zoom range.

Probably the main thing that bothers me is how does the image quality compare between these lenses in 18-70 range. Of course the fact that it has large aperture is very positive for me but the change from maximum zoom of 55 to 70 doesn't look very impressive compared to 250 or 270 mm.

Pardon me if you feel I am getting a little off-topic, but another benefit with the two-lens combo is that you would have wider apertures compared to a single large zoom - i.e. at say 70mm, you'd have a much wider aperture if 70mm is near the wide end than something in the middle.

I used to shoot with the EF-S 18-55 IS on my 550D, but recently I replaced this lens with a Sigma 18-50 f/2.8-4.5 HSM - while this lens is not much of an upgrade from the kit lens, I immediately noticed the improvement in IQ with this lens. Trust me, you'll appreciate the IQ when compared to the kit lens.

Another thing to consider here is the HSM on Sigma - while I don't have any experience with USM, based on my experience with the HSM (although not with any of the lenses in your list), it's much better than the stock focusing system on Canon - my 18-55 was particularly bad. As per the stabilization, I did not find much difference so far between the Canon IS and Sigma OS - again this is based on my limited experience with the Sigma 18-50.

I cannot vouch for the Canon 15-85 USM, but I heard a lot of good things about it.

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I've looked at SIGMA 18-50mm F2.8-4.5 DC OS HSM. Looking at the specifications it seems to be a really good lens. Especially I like internal focus and zooming. Am I right thinking that it doesn't extend during zooming? I've read that this is very useful since it prevents sucking dust and air inside the lens during zooming. But it is more than 2 times cheaper than SIGMA 17-70. That is very large difference. Is it that much worse? –  BartoNaz Jan 5 '13 at 2:06
1  
You are right - the lens doesn't extend during either zooming or focusing, and it is very useful not only keeping dust from getting inside, but also the front element doesn't rotate, keeping your (petal shaped) hood and CP filters in place as opposed to some lenses that do rotate when focusing. I've only got good things to say about this lens. The only thing I observed - although I don't complain - is it's not very fast when focusing in low light. I did hear it creates CA, but I have yet to experience that. –  Chaithanya M Jan 5 '13 at 2:23

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