Ok, firstly there's some obvious differences between the lens.. The most obvious is one is black and the other is white. The Sigma is also twice the weight of the Canon. Yet the Canon has IS functionality.
These aren't really accurate results, as a tripod wasn't used, I can't even remember if IS was on or off. But it was some quick clicking back in April when I shot these.
A noticeable thing is, Yes the Sigma is sharper, and it DOES have a warmer tone to the images. (actually now looking at them, I know the colour of the house etc, the Sigma is much more accurate, whereas the 100-400L is too cold looking)
As people have said in the past, you can make just about any lens take good shots at web size, but it's only when you go to 100% crop, you can see the difference.
First test, involved me shooting at approx 300mm at a house across the road...
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120-300 - F5.6 @ 300mm. Unedited.
As the first comparison, let's look at the same unedited shot taken with the 100-400L @ F5.6 (wide open)
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To me it's already noticeable the 120-300 wins.
Now let's take a closer look...
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120-300 @ F5.6
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100-400 @ F5.6
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Now this may be a tad unfair, as the 120-300 is now at 2 stops under, which is generally regarded as the sweet spot (2-3 stops under).. And the 100-400 is struggling as it is fully open.
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The second part of the test got me thinking, 300mm on the Sigma.. 400mm on the Canon.. I have a 1.4 x teleconverter, let's make things a little wilder, pretending in a real situation we do need that 400-420mm reach.
To display what I mentioned earlier, about the Sigma giving a warmer tone, take a look at these two examples:
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These don't need labelling to mention which one is warmer.
Every shot taken side by side, the Sigma clearly is warmer.. The 100-400 is bit cooler.. The real world situation I beleive is somewhere in between the two. So no one wins on perfect accuracy.
To make a little fairer, the two below are F8 crops.. Probably more of an even sweet spot on both the lens. However looking at all the shots, I would say the Sigma is sharpest on F5.6 - F8, and the 100-400 probably on F8-F11
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http://wazza.nfscity.com …20-300_f5-6_300mm_web.jpg
http://wazza.nfscity.com …-300_f5-6_300mm_crop1.jpg
http://wazza.nfscity.com …-300_f5-6_300mm_crop2.jpg
http://wazza.nfscity.com …00-400_f5-6_300mm_web.jpg
http://wazza.nfscity.com …-400_f5-6_300mm_crop1.jpg
http://wazza.nfscity.com …-400_f5-6_300mm_crop2.jpg
http://wazza.nfscity.com …120-300_f11_300mm_web.jpg
http://wazza.nfscity.com …0-300_f11_300mm_crop1.jpg
http://wazza.nfscity.com …0-300_f11_300mm_crop2.jpg
http://wazza.nfscity.com …100-400_f11_300mm_web.jpg
http://wazza.nfscity.com …0-400_f11_300mm_crop1.jpg
http://wazza.nfscity.com …0-400_f11_300mm_crop2.jpg
http://wazza.nfscity.com …20-300_420mm_f5-6_web.jpg
http://wazza.nfscity.com …0-300_420mm_f5-6_crop.jpg
http://wazza.nfscity.com …00-400_400mm_f5-6_web.jpg
http://wazza.nfscity.com …0-400_400mm_f5-6_crop.jpg
http://wazza.nfscity.com …120-300_420mm_f8_crop.jpg
http://wazza.nfscity.com …100-400_400mm_f8_crop.jpg
http://wazza.nfscity.com …120-300_420mm_f11_web.jpg
http://wazza.nfscity.com …20-300_420mm_f11_crop.jpg
http://wazza.nfscity.com …100-400_420mm_f11_web.jpg
http://wazza.nfscity.com …00-400_420mm_f11_crop.jpg
So the final verdict.
Both are great lens..
One is sharper, heavier and black.. But all in all, I'd consider them equal when you factor in the cost as well. The Sigma is probably 30-40% more expensive.
Just one final snippet to show the sharpness of the 120-300
http://wazza.nfscity.com/d1-r2/images/img_4038.jpg
and
http://wazza.nfscity.com/20d/fanga_crop.jpg
as the cropped version.
