|Datacolor DC SLC100 SpyderLensCal Lens Calibration System|
... the major points:
- Put different copies of the same lens on a single camera and each will vary a bit in resolution.
- Put different copies of the same camera on a single lens and each will vary a bit in resolution.
- Truly bad lenses aren’t a little softer, they are way softer.
- Autofocus isn’t as accurate as live view focus, at least when the camera has not been autofocus microadjusted to the lens.
What's interesting looking through these results is how much variability there is between lenses, even the same model. That's why things like Spyder's Lens Cal calibration system exist. The differences between copies may be slight, but you still want to get the best image possible out of your gear.