>
> >
> > > It's now obvious that the problem has not been the thickness
> > > of the M42 mount plus adapter, but instead is an internal
> > > problem with the 400mm f/6.8 T4 lens. Now I just need to
> > > find out how you adjust the infinity position of the focusing
> > > group inside the lens. This is not a real problem as I also
> > > have the 400mm f/5.6 TX version, and it works just fine.
> >
> >
> > Someone else may want to correct me but I suspect you might
> > find a screw under the rubber of the focusing ring that controls
> > the position of the focusing ring and infinity stop relative to
> > the front lens group. Loosening the screw may allow turning one
> > relative to the other then retighten.
> >
>
> The T4 lenses have machined aluminum control grips, but I will
> examine the focusing grip closely to see if there is a screw
> somewhere.
>
> According to the parts list and breakdown drawing that I have
> for the later 400mm f/5.6 TX, there are three set screws at the
> bottom end of the focusing collar that are not concealed by the
> rubber grip. And the focusing control stop appears to be a tab
> at the top end of that collar. It's very likely that the T4 is
> similar in design.
>
Nope, but there's other screws everywhere. I'll set that aside until I
can find out for certain how to adjust it.
Looking at the TX/T4 to M42 to OM 4/3 combined adapters, I can now see
that the proper thickness for the M42 to OM 4/3 adapter is somewhere between
6.0mm and 6.5mm, close to what you had calculated earlier. Mine is 8.0mm, so
I'll look around to see if I can find one of a more appropriate thickness that
doesn't cause problems with the aperture pin.
Chris
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