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09-13-2010, 08:08 PM   #1
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17mm vs 18mm (Tamron vs Sigma f/2.8 zooms)

How big of a difference is there on the wide end of these two lenses?

I've heard Sigma's 18mm is more like 19mm, but has anyone done a real comparison?

I saw brickwall tests here but it's kind of hard to tell with that kind of shot.


Last edited by Eruditass; 09-13-2010 at 08:25 PM.
09-13-2010, 09:29 PM   #2
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I think angle of view is what you are looking for:

78.8-31.2 for the Tamron 17-50 f2.8
69.3-27.9 for the Sigma 18-50 f2.8 EX DC Macro
72.4-27.9 for the new Sigma 17-50 f2.8

So the Tamron has the widest angle of view.

Regards,

Peter
09-13-2010, 09:49 PM   #3
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Thanks for that information, it's helpful, but I want to see what it means in a scene.
09-14-2010, 12:23 AM   #4
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QuoteOriginally posted by Eruditass Quote
Thanks for that information, it's helpful, but I want to see what it means in a scene.
I think that's asking the improbable. I don't think anyone would buy two fairly expensive lens with almost identical zoom range and speed to just to see which one has the widest angle of view. I certainly would not, but given the information kindly provided by Doanh I would be more inclined to buy the Tamron instead of Sigma.

Thanks,

09-14-2010, 04:57 AM   #5
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The Tamron is seen as the best of the two, generally. And the 16-50 from Pentax better than either.

I have the Sigma 17-70 and the Pentax 18-55 and I can confirm that 1 mm at the wide end is quite noticeable.
09-14-2010, 05:51 AM   #6
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I don't have time to do it right now, but the differences given in the post above have me wanting to shoot a comparison in angle of view at 17 mm between my Pentax and Sigma zooms. Six degrees difference in angle for two lenses at 17mm seems like quite a bit.
09-14-2010, 09:12 AM   #7
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QuoteQuote:
GeneV: I don't have time to do it right now, but the differences given in the post above have me wanting to shoot a comparison in angle of view at 17 mm between my Pentax and Sigma zooms. Six degrees difference in angle for two lenses at 17mm seems like quite a bit.

The published AOV for Sigma, I believe, is due to their using their sensor (in the Sigma camera) in the calculations. 17mm is 17mm.
09-14-2010, 02:53 PM   #8
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QuoteOriginally posted by excanonfd Quote
I think that's asking the improbable. I don't think anyone would buy two fairly expensive lens with almost identical zoom range and speed to just to see which one has the widest angle of view. I certainly would not, but given the information kindly provided by Doanh I would be more inclined to buy the Tamron instead of Sigma.

Thanks,
Many people have had both of these lenses at the same time and did many comparisons, usually focused on sharpness. So, I would not consider it improbable.

Thanks,

09-14-2010, 02:55 PM   #9
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QuoteOriginally posted by Jewelltrail Quote
The published AOV for Sigma, I believe, is due to their using their sensor (in the Sigma camera) in the calculations. 17mm is 17mm.
17mm is 17mm, but advertising is advertising.

Tamron 17-50mm F2.8 XR Di-II Test Photo Gallery by lightrules at pbase.com

QuoteQuote:
Sigma 18-50mm: 18.80-50.55mm f2.99-3.03.

Tamron 17-50mm: 17.36–50.37mm and f2.74–2.93

Last edited by Eruditass; 09-14-2010 at 03:47 PM.
09-14-2010, 03:13 PM   #10
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QuoteOriginally posted by Eruditass Quote
Now, what about their actual t-stops?
09-14-2010, 04:54 PM   #11
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QuoteOriginally posted by Jewelltrail Quote
The published AOV for Sigma, I believe, is due to their using their sensor (in the Sigma camera) in the calculations. 17mm is 17mm.
Yes and no. On a zoom, sometimes 17mm is 16.8mm and sometimes it is 17.4mm. As someone else said, avertising is advertising.
09-14-2010, 07:43 PM   #12
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QuoteOriginally posted by GeneV Quote
Yes and no. On a zoom, sometimes 17mm is 16.8mm and sometimes it is 17.4mm. As someone else said, avertising is advertising.
I don't think that's at all unique to zooms.

Paul
09-22-2010, 11:05 AM   #13
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QuoteQuote:
GeneV: Yes and no. On a zoom, sometimes 17mm is 16.8mm and sometimes it is 17.4mm. As someone else said, avertising is advertising.
Zooms are, of course, dependent upon where they are focused: 50mm focused at infinity is not the same 50mm focused elsewhere. AOV is calculated with the sensor dimensions in the mathematical formula. It is expected that Sigma publish figures with its sensor.
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