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Old Jan 27, 2007, 9:47 AM   #1
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I got a Sigma 24-70mm 2.8 EX and a few things bug me about it
1. large
2. heavy
3. slow focus
4. there are times when it is not wide enough
5. soft wide open

I tried a Sigma 17-70mm in a store and liked it. It looks sharper then 24-70mm at all appertures. It is small, and focus is very fast and silent compared to 24-70mm.

I shoot my daughter's dancing - the conditions are not perfect: low light and the subjects move fast. I use flash. I always shoot at f4 to get more or less decent results as at 2.8 it is just too soft.

Now the question - whoever owns or had experiences with both 24-70mm and 17-70mm - chime in and tell me what you think about the two lens when compared to each other. I have not done any shooting with 17-70 in field conditions. I am thinking - if 17-70mm is as good as mine at everything mine does and goves me wider angle, faster focus and hopefully better sharpness - I'd sell 24-70 and get 17-70.


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Old Jan 27, 2007, 11:31 AM   #2
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You don't need to own the lenses :idea:

-> according to the MTF a 'digital' (17-70 DC) lens is almost always sharper than a full-frame (24-70 EX)!

17-70 @ 70mm



24-70 @ 70mm



--> Ditto at the wide
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Old Jan 27, 2007, 11:59 AM   #3
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but surprisingly the 24-70 EX is better on a 20D over a 5D.
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Old Jan 27, 2007, 12:15 PM   #4
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I have the Sigma 17-70 that I use on my 20D. I also use a 70-200 Canon 2.8L so I have a good comparison. Of course, I can tell the difference between the two but I am very happy with the Sigma. I tried to attach a portrait I took of family members/ I also shot a friends rehearsal dinner outside last month with it and took 80 or 90 group shots and candids with it. I used my 580 EX flash with a Stofen diffuser (looks like a white cap) and was very pleased with the prints. My "skin tones" were good and sharpness wasn't an issue at all. For the cost the lens is a great value. The little bit Extra width on the 17 side is handy also.

Best of luck and Happy shooting!

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Old Jan 28, 2007, 8:11 AM   #5
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nymphetamine wrote:
Quote:
but surprisingly the 24-70 EX is better on a 20D over a 5D.
... and you can observe this phenomenon on the MTF as well!
a 20D is blind to anything above 13mm on the horizintal axis (because the crop factor), but the 5D see everything all the way to the corners: Both the contrast and sharpness start to fall off near the edge on a 5D which is typical of most full-frame lenses where the incoming light has to strike the sensor at steeper angles

-> A 'digital' lens only needs to perform only to the ~13mm (i.e. 1.6x crop fator) hence their designs are optimized for higher contrast/sharpness by having the light striking the sensor more straight on which BTW also reduce the size and bulk of the lens!

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Old Jan 28, 2007, 11:05 AM   #6
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hence guessing the optimal crop is 1.3x

style="BACKGROUND-COLOR: #000000"best for both worlds, tele and wide. i have a 5D, but would love to get a 1.6X Pro series if they release one.

style="BACKGROUND-COLOR: #000000"I am hoping they shud move the 1d Mark II to 1.6x with a 10mp sensor. It would be a great camera with 9fps
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Old Jan 28, 2007, 3:44 PM   #7
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I sold my EF-S 17-85 IS, and bought the Sigma 17-70 it is a better lens than the 17-85 i am really happy with the Sigma.
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Old Jan 29, 2007, 1:57 PM   #8
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17-70mm looks like a winner then .... may be I will sell my 24-70 and get 17-70 instead.
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Old Jan 29, 2007, 2:18 PM   #9
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well I very happy with my 24-70mm and I use the 2.8 at the 70mm end a lot, so the 17-70mm doesn't quite fit my needs. As far as focus speed, mine seems to be pretty darn fast, so I don't quite understand the slow focus problem you are having. But then I have a couple of other lenes to cover the wide angle problem you have, so the 17mm is not as important to me as it may be to you. As far as being soft at f2.8, again mine is tack sharp on the object I'm focusing on, yes the background is soft or out of focus, but then it is supposed to be.


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Old Jan 29, 2007, 3:31 PM   #10
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I shoot low light indoors sports. Many shots are softer then I'd like them because by the time it takes to focus the subject has moved + the lens produce softer results in general .... Yesterday I diched the Sigma 24-70mm and used only 50mm 1.8 at 2.8 - even though it is not the fastest focusing lens in the world - I got a lot of great shots like these 3 (I could never ever get such shots with Sigma - example is the 4th image)








for example ... here is the shot with my Sigma 24-70 at f4.5, 70mm


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