Mycroft
23rd of March 2006 (Thu), 04:51
My used Sigma 70-200mm f/2.8 APO EX HSM (non-DG) lens arrived today (YAY!). :D :D :D
However, upon shooting a few quick pics, I noticed that it was blurry (more than just soft) at 135mm and 200mm at f/2.8 (shutter speeds in excess of 1/2000s). I tried stopping down, and the lens didn't get sharp enough to be usable until f/8 or so. :evil: Frustrated, I went to work, thinking about the bum lens all day. It actually affected my performance at work. I was feeling very distracted. :cry:
Just a few minutes ago I was playing with the lens again, and noticed that it was MUCH sharper at f/2.8 now. After a few quick experiments, I have determined with fair certainty what the mode of failure actually is; However, I have difficulty explaining it... For the sake of example, let us assume that the actual focus point is 5 meters. When the lens starts focussing anywhere on the side closer to infinity (that is, anywhere between 5m and infinity), it attains sharp focus. When the lens starts focussing on the opposite side (that is, from 1.8m to 5m), the image is so out of focus as to ruin the shot. Center focus point selected, and focus acheived according to indicator light.
All my other lenses focus just fine, and always have. Is this merely a calibration issue with the lens, or is the problem more complicated than that? Has anyone experienced this same issue with this same lens? How much did repairs cost? What was the turnaround time? (I REALLY do not want to have to wait -ANOTHER- six months to get a lens properly repaired. Canon took 24 weeks to correctly repair the 75-300mm IS lens that I recently sold on ebay. Once bitten twice shy.)
attached are 100% crops unprocessed.
However, upon shooting a few quick pics, I noticed that it was blurry (more than just soft) at 135mm and 200mm at f/2.8 (shutter speeds in excess of 1/2000s). I tried stopping down, and the lens didn't get sharp enough to be usable until f/8 or so. :evil: Frustrated, I went to work, thinking about the bum lens all day. It actually affected my performance at work. I was feeling very distracted. :cry:
Just a few minutes ago I was playing with the lens again, and noticed that it was MUCH sharper at f/2.8 now. After a few quick experiments, I have determined with fair certainty what the mode of failure actually is; However, I have difficulty explaining it... For the sake of example, let us assume that the actual focus point is 5 meters. When the lens starts focussing anywhere on the side closer to infinity (that is, anywhere between 5m and infinity), it attains sharp focus. When the lens starts focussing on the opposite side (that is, from 1.8m to 5m), the image is so out of focus as to ruin the shot. Center focus point selected, and focus acheived according to indicator light.
All my other lenses focus just fine, and always have. Is this merely a calibration issue with the lens, or is the problem more complicated than that? Has anyone experienced this same issue with this same lens? How much did repairs cost? What was the turnaround time? (I REALLY do not want to have to wait -ANOTHER- six months to get a lens properly repaired. Canon took 24 weeks to correctly repair the 75-300mm IS lens that I recently sold on ebay. Once bitten twice shy.)
attached are 100% crops unprocessed.