I finally decided on the above lens..given my goals (strictly amateur bird, wildlife photography for personal enjoyment) the price/performance of this lens couldn't be beat. That being said, I had heard that depending upon the specific lens obtained variation in manufacturing QC can affect a particular lens' performance; i.e., better make sure I have a good copy....therefore, I ran a series of tests using a flat highly textured surface as a test sample.
I took a series of shots using a tripod with OS off as well as remote with mirror up function. 5 shots at 30 feet and 5 additional at 15 feet. Camera set to manual: shutter speed of 1/500 for 15 foot and 1/1000 for 30 foot; f6.3 (wide open), f8, f11, f16, f22. ISO rose from 125 to 1000 for 30 foot shots and 100 to 640 for 15 foot shots. Nice bright day, sample in full sun.
Summarizing Impressions: at 30 feet, results (inspection at 1:1 on screen) were fairly consistent. Certainly sharp enough, but not like a lens costing considerably more. At 15 feet the results were not as consistent. Up to f11 the results were not usable in my opinion, blurry, loss of detail. That being said at f11 and above (stopped down) the results were stellar. Really sharp.
Bottom line: stop this baby down!
Hope this helps someone...FWIW
I took a series of shots using a tripod with OS off as well as remote with mirror up function. 5 shots at 30 feet and 5 additional at 15 feet. Camera set to manual: shutter speed of 1/500 for 15 foot and 1/1000 for 30 foot; f6.3 (wide open), f8, f11, f16, f22. ISO rose from 125 to 1000 for 30 foot shots and 100 to 640 for 15 foot shots. Nice bright day, sample in full sun.
Summarizing Impressions: at 30 feet, results (inspection at 1:1 on screen) were fairly consistent. Certainly sharp enough, but not like a lens costing considerably more. At 15 feet the results were not as consistent. Up to f11 the results were not usable in my opinion, blurry, loss of detail. That being said at f11 and above (stopped down) the results were stellar. Really sharp.
Bottom line: stop this baby down!
Hope this helps someone...FWIW