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Old Apr 14, 2006, 5:30 PM   #1
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I am looking for a good walk around lens. I am having hard time deciding between these three lenses:

Canon 17-85mm IS - I like the range but tests reports are not too flattering on sharpness and CA

Sigma 17-70mm - I like the focal range but have not seen test reportson sharpness and focus speed since it is fairly new lens.

Sigma 18-50mm f/2.8 - Like the f/2.8, sharpness but not sure about it focusing speed/accuracy. Also not sure if it is really sharper than 17-70.
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Old Apr 14, 2006, 11:28 PM   #2
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The May issue of Popular Photography has a test on the Sigma 17-70mm, it doesn't look too bad. The test report may even be on the web page, but I have not checked to be sure. I have the sigma 18-50 f/2.8, and it is a pretty nice lens, but I think personally for a walk around I would like the extra reach of one of your other two choices.
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Old Apr 15, 2006, 2:22 PM   #3
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I do not want to look pushy or something, but in some of the previous two topics I've mentioned that I am using Sigma 17-70 on my new 30D and only thing I can say that I am completely happy with it! I was also looking at the tests for other lenses around the web but this was my choice.


-Price, range, macro, F2.8 at 17, sharp, solid build, good focus, very low fringing, ghosting etc. Not to match loss of sharpenss at 2.8 (80% in the corners)


-Not as fast as Canon, but fast enough; I do not consider this lens as 'action' lens anyway.


-More contrast than Canon lens; depends what you prefer; it is also a bit 'warmer'

-Some barrel distortion at 17, but something to expect from any lens at this range
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Old Apr 16, 2006, 11:34 AM   #4
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I checked Popular Photography web site but they do not have test report of the Sigma 17-70mm posted.

It would be great if anyone have done comparison review of these 3 lenses.
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Old Apr 16, 2006, 1:15 PM   #5
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Just do search on Google. There are comparison tests and they will show on first or second page of search result. In general, test comparison between Sigma 17-70 and Canon 18-85 IS is this:

Sigma: sharper at wide end, much better macro capabilities, warmer, more contrast

Canon: sharper at tele end, faster AF, bit better range (85 comparing to 70)

Both lenses are digital only. I did not want to pay more for Canon, knowing that there is no difference in optical quality. For difference in speed in this 'wide' 17-70 range I do not care personally. Also, I consider anything digital not to be so good investment so I tend to want to pay less. But also I want quality. So I bought 30D over XT and Sigma over Canon, which is in may opinion as good as Canon and overall better (price, capabilities).
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Old May 22, 2006, 10:05 AM   #6
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I invite you to consider the Tamron 28-75. f2.8

I just bought it last week and it's perfect, just a little bit heavy, but it's ok for me.
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Old May 22, 2006, 10:52 AM   #7
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I was in a similar position as you. 17-70 or 18-50 sigma. I decided to get the 18-50 sigma primarily due to the slightly better sharpness, contrast, constant 2.8 aperture, slighty better build quality, and less vignetting (all compared to the 17-70).

That said, the 18-50 has a little worse CA than the 17-70 andless range.

It is more about do you want a little extra quality or a little extrarange? Both are good choices. Keep in mind the 17-70 has a macro of 1:2.3 (pretty good)verses the 18-50's 1:5 (not as good). Note, true macro is a 1:1 ratio.

From my research on these two lens is that they are both fairly fast at AF. There have also been reports of duds that need to be returned and or fixed for focusing problems (though I wonder how many of these "reports" are operator errors instead of lens defects and not to metion people are more inclinded to post problems in forums compared to when everything is going well).

I suggest you read my post regarding my contemplation of these two lenses (as well as the 24-70). I have various links to reviews for both the 17-70 and 18-50.


Here were my conclusions about the two lenses:

18-50 EX PROS (effective to 29-80mm)
2.8 constant (can use indoors, weddings, etc)
Lower vignetting than 17-70
Lower barel distortion than 17-70
Higher Resolution (just about as good at 17-40L)
Better contrast than 17-70
Better Build than 17-70
usable f2.8 (except see con below)

18-50 EX CONS
Smaller range than 17-70
Macro is 1:5 vs. 1:2.3
More CA-Red and especially CA-purple than 17-70
soft corners at 18mm f2.8 (but only on exterme border 85% off center)

17-70 DC PROS (effective to 27-112mm)
2.8-3.2 aperture in the 17-24 (which means indoor low light ability at 27.2 - 38.4mm)
Better range than 18-50
Macro is 1:2.3 vs 1:5
Build quality almost as good as 18-50
Less CA-Red and CA-Purple than 18-50

17-70 DC CONS
Not as sharp (but not to a huge degree)
more vignetting
more barel distortion
worse contrast than 18-50
F2.8-3.2 quite soft at corners (overal morso than 18-50)

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Old May 22, 2006, 3:11 PM   #8
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I agree, the Sigma 17-70 looks to be at least as good as the Canon optically, so what you're paying for is:

1. Image Stabilizer
2. USM (which makes a pretty substantial difference to me).
3. The Canon brand (which means if something is wrong I know who's fault it is).
4. Slightly bigger zoom range.
5. Sharper at wide aperture at the telephoto end (at the wide end it's more likely to be used stopped down anyway).

That explains the difference in the price. There is no way of saying one lens is better overall than the other. Every lens has a dozen characteristics by which it can be measured, and they all are different.

It depends on the individual's needs and likes as to which makes more sense. The 17-70 is not a bad choice at all, nor the 18-50, but nor indeed is the 17-85.

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Old May 22, 2006, 4:16 PM   #9
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Guys, I just ran across the 17-50 tamron 2.8 review. It appears to be great with the major exception of it's focal plane not being even:


Compared to the 18-50 2.8 sigma I already ordered It makes me wonder if the tamron is better (of if the sigma copy the reviewer had wasn't as good as the tamron). In any case B&H doesn't have the tamron in stock yet and when it does it will be $40 more. Nevertheless this is interesting.
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Old May 23, 2006, 6:19 PM   #10
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Thanks guys for all the good information. I have bought Sigma 17-70 and am quite happy with it for now until I learn more about Digital photography...
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