Ignore unsubstantiated comments
It’s important when reading comments online to maintain an extremely skeptical view of most of them. Comments might summarily dismiss a lens or other piece of equipment as no good. I came across this dubious posting recently, referring to the Canon EF 50mm f/1.2L:
Don't buy the new 50mm f1.2. You will be very disappointed.
The poster provide no details, a strong clue that cluelessness is more likely. It takes skill and expertise to evaluate a lens. Perhaps this person has that ability. And perhaps that person actually owned and used and tested the lens. Or perhaps not. Or maybe he had a defective sample, but was unable to recognize that the lens was defective. Or maybe the focus was inaccurate. At any rate, there is absolutely nothing to back up the claim; is the poster referring to resolution/contrast, flare control, distortion, focus speed, what?
The Canon 50mm f/1.2L is actually an excellent performer. At f/1.2 (wide open) on the 16.7-megapixel Canon EOS 1Ds Mark II in the extreme corner (outside even a 1.1X sensor crop), the lens can resolve to the limits of the sensor; the “30” bars seen below are the resolution limit on the particular test target that I used for that resolution sensor; the “35” bars cannot be resolved by any lens at any aperture on the 1Ds Mark II.
Actual pixels @ f/1.2, center, mid, extreme corner
(full-frame 16.7-megapixel Canon EOS 1Ds Mark II)
Resolving power in the area mid-way between the center and corner is a bit blurry, but this might be due to field curvature, or it might just be that the lens really is less sharp there, or it might be that my sample is slightly off somehow.
