Teleconverer trouble

[a_scayola]

Hi,
I recently bought a Vivitar 2x teleconverter and it doesnt seem to go very well with the intended lens, a 75-205 Hoya. I cant focus on infinity. I've tried zooming in and out, different apertures and its the same thing.
However, the teleconvertor works perfectly on my Hanimar 135mm; no focus problems at all.
Anyone has an idea of why this happens, and if there is a way to fix it?

By the way, I'm using this lenses on a manual-only zenit camera.

Thanks for your help,
Andres

 

[a_scayola]

Any ideas, anyone?

 

[Big Mike]

I don't know but I would guess that the TC does not work as well with the slower zoom lens as it does with the 135 prime. Sorry I can't be of much help.

:edit:

What I meant to say is that maybe the zoom lens does not have a big enough aperture for the TC to function properly. A 2X TC will usually cost two stops of light...which will make the viewfinder darker and harder to focus.

 

[a_scayola]

Thanks for the reply.

 

[photobug]

How far back does the rear element of the lens protrude? It may be that it's just too close or too far away from the teleconverter element to work properly.

 

[a_scayola]

Well, the rear elemen doesn't seem to protrude at all. It's flush with the body of the lens. Only the thread protrudes back.
I thought about the distance being a problem, but the teleconverter doesnt seem to be adjustable at all, and I havent seen any kind of "spacer" rings for this.

Any more ideas?