While I agree with EvH immensely that many (most?) CLA does not include rigourous "A" I feel obligated to mention that 30% error is for some professional shutters within the original specification.
Originally Posted by mgb74
It seems to me that most shutter overhauls clean and lubricate with the assumption (good in most cases... in my experience) that those two activities will restore the original capability and specs.
For me a half-stop is still relatively insignificant and the most useless tool I -- personally speaking -- could ever buy is a shutter tester that might evoke my currently-repressed shutter-speed neurotic tendencies/anxieties.