What is the difference between these 2?

marine1 said:
I just dont get how the Sony can be so much more :confused:
I played with the Sony the other day, very nice but not double the price nice.
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Have you played with the sigma then?

Are either/both of these lenses weather proofed? I can only speak for canon glass but I've noticed the build quality to be superior so you might want to take that into account. Sigma glass comes with a three year warranty which you'll probably need to take advantage of - at least I have.
 
Check the photozone reviews for the Sony and Sigma. Bear in mind that the Sony is tested on a higher MP body, so the resolution figures are not directly comparable.

Also keep in mind they write that their Sigma was slightly de-centered. That probably accounts for the drop in resolution at f/2.8 at longer focal lengths (as DOF decreases).

Both are excellent but I'd say at that big a price difference the Sigma is at at least worth a try. I've heard nothing but good things about it.
 
From what I've read about lenses in general, the Sigmas tend to have a large variation in their production quality. Most will advise to test the lens before you buy. If its a soft copy... test another one. I personally don't have a good eye for this, so I stick with Canon. But Sigmas do offer good value for money.
 
SubliminalThought said:
From what I've read about lenses in general, the Sigmas tend to have a large variation in their production quality. Most will advise to test the lens before you buy. If its a soft copy... test another one. I personally don't have a good eye for this, so I stick with Canon. But Sigmas do offer good value for money.
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Canon has product variation too. Sigma just has a much worse reputation because of a history of this but it's much much better now.
 
Get the sony from B&H? No duties on glass :)
 
1. Resolution. They measure the number of "line widths per picture height." This tells us how much detail the lens resolved from the sensor's perspective. Hypothetically, a 6MP sensor would only resolve half the detail of a 12MP sensor of the same size with the same lens, so if you test with a 12MP camera, the number of LW/PH will be higher than on a 6MP sensor. For reasons that I don't understand well enough (yet) to explain it to someone else, this doesn't scale linearly, so you can't take the test results from a 6MP sensor and simply double it to get comparative results for a 12MP. For one thing, the lens might not be good enough, but there are other factors.

That's why I said you can look at the trend, i.e. look at he bar graphs and check where the resolution falls in the bad/average/good/excellent bands

2. De-centering roughly means that the image doesn't fall entirely level on the sensor (I may have this slightly wrong, but that's the effect). At smaller apertures, where you have more DOF, this may not matter too much, but at f/2.8 on a tele lens, this can be a significant issue. That's why I mentioned that, in that review, they're getting a resolution drop at f/2.8, but not really at smaller apertures, and they specifically mention the de-centering, so to my mind, that may be the cause (given that the lens returns excellent resolution otherwise). I'm speculating, of course, but I've seen shots from that lens and I've seen other reviews, and it's very good.

De-centering can happen to any lens by any manufacturer. My Canon 28-200mm has it (which is why I don't use it). My Sigma 10-20 got de-centered after about six months, most likely due to my (mis)handling of it. Sigma replaced it under warranty, no questions asked.
 
marine1 said:
Thanks Bwana, the main reason for me wanting this is for low light shooting say at a function.
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I was going to say that's a particular range for an evening function but then I realised I've used the same range myself. That's only an f/4 of course. :)
 
So in your expert opinion that would be the best lens for functions at night?
I seem to go to many birthdays, etc and it is such a ball ache to use my Sigma 18-200, just doesnt cut it
Awesome shot,
 
I'd look for whatever Sony has in the 17-55 f/2.8 range or the Tamron 18-50mm f/2.8 which is a sharp lens and not too expensive. Maybe it's just me but I find at functions/parties I often don't have foot zoom space. Hardly any of my party shots are over about 40mm.
 
marine1 said:
So in your expert opinion that would be the best lens for functions at night?
I seem to go to many birthdays, etc and it is such a ball ache to use my Sigma 18-200, just doesnt cut it
Awesome shot,
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I'm more opinionated than expert but . . . I'm a huge fan of a fast 50mm. I'm planning on shooting a wedding with it in December I will have a 24-70mm on a separate body just in case I'm not feeling it on the day.

Apart from that I dont really know what's available for Sony.
marine1 said:
Settings?
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Canon 1DMark 3, Aperture Value: 4, Color Space: sRGB, Custom Rendered: Normal process, Date Time Digitized: 2009:09:02 21:35:18, Date Time Original: 2009:09:02 21:35:18, Exif Version: 2.2.1, Exposure Bias Value: 0, Exposure Mode: Manual exposure, Exposure Program: Manual, Exposure Time: 1 / 60, Flash: Flash did not fire, compulsory flash mode, FlashPix Version: 1.0, FNumber: 4, Focal Length: 70, Focal Plane Resolution Unit: inches, Focal Plane X Resolution: 3512.195, Focal Plane Y Resolution: 3521.739, ISO Speed Ratings: 1000, Metering Mode: Pattern, Pixel X Dimension: 426, Pixel Y Dimension: 640, Scene Capture Type: Standard, Shutter Speed Value: 6, Sub-second Time: 33, Sub-second Time Digitized: 33, Sub-second Time Original: 33, White Balance: Auto white balance
 
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