Wayne Harridge wrote:
> You probably need to check that it is stopping down fast enough - could be a
> sluggish diaphragm.
> (just had a Nikkor repaired with this problem !)
>
Nope, the Tamron adaptall design is like Zuikos, the diaphragm is held
open by the spring and pushed closed by the aperture actuation lever. So
slow/sticky diaphragm blades leave the aperture closed or opening too
slowly and lead to underexposure.
Nikon is the opposite, using the spring to close the blades and the
lever to open them when the lens is attached, then allow the spring to
close them for exposure, so a sticky diaphragm will tend to overexpose.
Moose
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