In article <3282e6a1.2250277@news.wiscnet.net>, galta@gbms01.uwgb.edu says...

>I have a 50 mm f/1.4 Nikkor that I do not use very much. The barrel has "been
>around the block," and I suspect the lens saw considerable use, but the glass
>itself is essentially perfect. The problem with the lens is that when it stops
>down, the shape formed by the blades of the diaphragm is not a symmetrical
>hexagon. One side is slightly longer than the others. It does not seem to be
>a matter of dirty or oily blades -- the diaphragm snaps open and shut with no
>problem and I don't see any oil or grime through the front or rear elements. I
>wonder whether and how much this is likely to affect exposure and whether it
>is something I should have looked at by a repair man. I have seen this sort of
>thing on quite a few SLR lenses, so it must be something repair people deal
>with frequently. Any sage advice would be welcome.

Most people don't worry about it, unless it results in innacurate exposure.
Try shooting three slides, one at f8, one at f11, one at f16 - of the identical
subject (adjusting the shutter speed [preferably in Manual mode] to produce
what should be the same exposure. Repeat with a subject that uses a different
set of shutter speeds (to reduce the possibility of exposure error due to the
shutter and not the aperture). If virtually no difference can be seen in the
slide exposures, don't worry about it. BTW, if your camera allows "stop-down" reading, variations from correct diaphragm area won't matter using this type
of metering since the metering is done through the actual diaphragm opening,
not the camera-simulated aperture value.
Hope This Helps