Yes, this is correct. It's also unacceptable, I've always felt it was a weasel tolerance. I need to know that my exposure will be what I expect; transparency film will not tolerate much error, and black and white is the same if you are using it's entire tonal range.. Is 30% error acceptable in a lightmeter? No. Aperture calibration? No. Then why on shutter speeds? I've never had a problem getting the speeds within the 10 to 15 percent tolerance I mentioned above, with the exception of the one or two higher speeds on leaf shutters, which will be consistent but slower than the marked speed.
Originally Posted by BrianShaw