Originally posted by cmohr Hmm, seems odd, sounds like there may be something slightly amiss between the actuator in the camera that stops down the lens and the lever on the lens itself that holds the blades open. Because if it all seems to open correctly off-body and doesn't feel sticky or slow I wonder If that lever on the back of the lens had even a slight bend in it, that could cause this kind of problem because it would not be positioning correctly with the lever in the camera body.
I would think that this is the problem. The aperture actuation lever movement is designed to be proportional to the area of the aperture in "A" lenses forward, and if the lever is either bent or worn, it's possible that it is not engaging accurately.This also could be true of the actuating lever on the body, BTW. 1/3 to 1 stop is actually a pretty small difference in the movement of the lever.
The bottom line is how much this will practically limit your ability to use the lens effectively. If you would regularly be shooting this with Auto aperture control at f stops over f1.4 and wider than f2, then it would be worthwhile to have it calibrated by a pro lens tech. If you would normally shoot this lens stopped down past f2, then I wouldn't bother. I realize that it's normal to expect a costly legendary lens to perform superbly in every respect, but if there is no actual practical downside, then why let something that really doesn't matter cloud you perception of the lens' quality? I find that confidence in my gear effects the way I shoot and the results I get.
Working around this does not seem to be much of a problem. At these apertures, framing and metering stopped down 1/3 to 1 stop is not really much of a working handicap, and critical focusing might actually be more accurate since it would be done with the lens physically stopped down.
If this actually practically effects your shooting, then I'd make the investment to have the aperture lever calibrated to the body or work around it. If not, then I wouldn't let this relatively minor fault mar my impressions of a superb lens.
Scott