Re-focusing a Teleconverter?

Scheimpflug · Expire: 2011-11-18

Does anyone have any tips on how to re-focus a teleconverter?

I've found that with my Soligor, a lens on the end of it can't quite focus as far out as normal. So my lenses with accurate hard-stops at infinity can no longer focus to infinity with the TC mounted.

I've confirmed that it isn't just a TC sharpness issue, as I have a lens which normally focuses past infinity, which can just barely still focus to infinity on the TC.

The optics in this Soligor are all one set, so I can't adjust the elements independently... however, they are mounted in a small threaded tube which can be adjusted forward/backward.

The question is... how do you best adjust this? I could turn it small amounts and keep checking it, but that requires dismounting & remounting the lens & TC each time... is that the best way?

Thanks

unclemack · Joined: 21 Jun 2009 Posts: 51 Location: UK frozen north

You don't say what fitting it is. I imagine you've already checked the security of its front & rear mounts
Assuming you bought this secondhand it's possible a previous owner has adjusted it for a different mount, maybe with an adapter.
If the one-piece cell can be screwed in/out easily then it probably has been moved - usually the threads are locked with lacquer which can be softened or removed with acetone & other solvents.
Trial & error would seem to be the only option open to you. Mark the relative positions before you start & keep good notes so that if you have to make a small adjustment to the setting later you're not starting from scratch, ie. you know which way to turn it and by how much.
I set mine to allow focus a little "beyond infinity" but you don't have to.

Scheimpflug · Expire: 2011-11-18

It was a 3x Soligor for a Nikon mount. I actually have another thread about it over here:
http://forum.mflenses.com/soligor-3x-tc-wont-mount-to-nikon-d40-t26530.html

In fact, now that I think about it, it could be possible that the defect in the barrel that kept it from mounting might have also caused it to be calibrated wrong at the factory... hmm...

The suggestions to make some reference marks and to adjust for a smidge past infinity are both great ideas. Thanks!