Is it okay to use a T-Con 1.7 Teleconverter with a Nikon D3100 via a step-up ring?

Question

I've recently bought a Nikon D3100 with 18-55mm kit lens. I already have an Olympus T-Con 1.7x teleconverter and would like to connect it to the kit lens with a step up ring.

My concern is that the teleconverter is pretty weighty and I'm worried it might break the mechanics powering the auto focus on the focus ring at the end of the lens as it will have to rotate the teleconverter too.

Do you think this would be okay or not?

Answer

I doubt this would work.

Nikon and Olympus (I'm assuming your teleconverter is for the OM system) do not have the same register - the distance between the lens mount and the sensor. While you can adapt OM lenses for use on Nikon by physically replacing the mount, and you may be able to mount a Nikkor lens on an OM body by using an adapter, you're looking at a very hacky solution indeed.

In addition to this, the kit lens is not well adapted for teleconverter use. You'll get a rather wimpy focal length of 55 x 1.7 = 93.5mm, and lose 2/3 of a stop, so it will be a 93.5mm f/6.3 at the long end.

If you want a longer lens, I'd recommend you get an older Nikkor if you're strapped for cash, or the Nikkor 55-300mm DX zoom or its Nikkor 55-200mm DX predecessor.

EDIT: as @EvanKrall mentions in a comment, this isn't a "normal" teleconverter, that fits between the body and the lens, but a teleside converter, designed for a compact camera. To be honest, I don't know if this can work at all. Filter-side converters are pretty common on high-end compacts, as they have the mounting bayonets and good optics that can take advantage of them. But compacts in general have a much smaller sensor and their lenses are constructed for a smaller coverage.

I once again doubt this could work, but you may try to see if you get decent results simply by holding the converter in front of the lens and seeing if the image looks OK. Don't forget to try to focus to infinity, I suspect this is the sticking point.

My original answer still holds, however, if we had a hypothetical 1.7x teleconverter for the OM system.

Check more discussion of this question.