From: infiniteMPG on
I have a Sony Alpha A-100 DSLR camera and a nice Tamron AF 18-250 DiII
zoom lens. Recently I bought a nice Tamron 90mm f2.8 telephoto to use
for macro shots and also bought a 2X Teleplus converter to get in real
close, all manual focus of course. Works great! Even will autofocus,
too. Curiosity got to me and I slapped the 18-250 on the 2X converter
and even in manual focus mode, it feels like the focus ring is locked
and like I'd be grinding things if I forced it to focus.

Kind of thought when this camera in manual focus mode that the focus
ring drive would be totally disengaged.

Any hints on what's going on and how I could use this adapter with the
18-250 lens?????

Thanks!
From: Peter on
"infiniteMPG" <57classic(a)gmail.com> wrote in message
news:0571b4e4-d4ae-4a12-bc56-2b27f0c69faf(a)p17g2000vbe.googlegroups.com...
>I have a Sony Alpha A-100 DSLR camera and a nice Tamron AF 18-250 DiII
> zoom lens. Recently I bought a nice Tamron 90mm f2.8 telephoto to use
> for macro shots and also bought a 2X Teleplus converter to get in real
> close, all manual focus of course. Works great! Even will autofocus,
> too. Curiosity got to me and I slapped the 18-250 on the 2X converter
> and even in manual focus mode, it feels like the focus ring is locked
> and like I'd be grinding things if I forced it to focus.
>
> Kind of thought when this camera in manual focus mode that the focus
> ring drive would be totally disengaged.
>
> Any hints on what's going on and how I could use this adapter with the
> 18-250 lens?????
>


The lens is probably designed so that the rear element is touching the 2x
converter. To solve that issue I have successfully used the Kenko 1.4
converter on other lenses, the Nikon 18 -200 and the Nikon 80-400, with that
issue. From your description of the problem I suspect you have the same
issue with your Tamron.

HTH

--
Peter