I saw some folks (@Ironwood) here call for comparisons and tests with the Sigma 120-300...so I obliged 
So I recently acquired a new to me Sigma 120-300 f2.8 Sport lens. The lens feels and handles great and is a joy to use. Be sure though to upgrade to the latest FW. If it stays on the 1.00 FW it is sluggish and behaves oddly.
To the test. I tested the bare lens, with the 1.4TC and with the 2xTC. The TCs used were the old APO DG variants, since I don't have the new ones. Optically they are suppose to be the same, the new ones just work with the dock.
I tested it the way I would most normally use it in the field. All the focal lengths were shot from the same distance to the target, which was roughly 7 meters (23 feet). I did change the exposure though, so all the variations have the same ISO (100). I exported JPGs with Lightroom, leaving sharpness at the default 25 setting. I adjusted white balance as well.
I will let you draw your own conclusions.
Below are 100% crops of 300mm at f2.8, f3.2, f4, f5.6 and f7.1; 420mm at f4, f4.5, f5.6, f7.1 and f8; 600mm at f5.6, f6.3, f7.1 and f8
300mm comparison:
420mm comparison:
600mm comparison:
Full files available for download at: http://www.bobr.si/fotke/s123sport_test.zip
Sorry for the large images, but I did not want the uploader here removing detail
So I recently acquired a new to me Sigma 120-300 f2.8 Sport lens. The lens feels and handles great and is a joy to use. Be sure though to upgrade to the latest FW. If it stays on the 1.00 FW it is sluggish and behaves oddly.
To the test. I tested the bare lens, with the 1.4TC and with the 2xTC. The TCs used were the old APO DG variants, since I don't have the new ones. Optically they are suppose to be the same, the new ones just work with the dock.
I tested it the way I would most normally use it in the field. All the focal lengths were shot from the same distance to the target, which was roughly 7 meters (23 feet). I did change the exposure though, so all the variations have the same ISO (100). I exported JPGs with Lightroom, leaving sharpness at the default 25 setting. I adjusted white balance as well.
I will let you draw your own conclusions.
Below are 100% crops of 300mm at f2.8, f3.2, f4, f5.6 and f7.1; 420mm at f4, f4.5, f5.6, f7.1 and f8; 600mm at f5.6, f6.3, f7.1 and f8
300mm comparison:
420mm comparison:
600mm comparison:
Full files available for download at: http://www.bobr.si/fotke/s123sport_test.zip
Sorry for the large images, but I did not want the uploader here removing detail
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