Pentax 1.7X Teleconverter question

Looking at my lenses atm most of them are manual focuse so I am toying with the idea of buying a Pentax teleconverter to make them auto. This would then make my favourite Vivitar macro lens auto and so it would save me having to buy a AF macro lens.
My question is can you use the converter purely as a AF adapter without the teleconverter side of things which would degrade the IQ of the lens.

Thanks

No you can't. The lens has been moved away from the camera by inserting the TC so optics are required to accommodate this. The result is a 1.7x increse in focal length.

Ah well, thats another idea out the window .. thanks for that

How does the quality of the lens hold up with the converter then as it would make the 100mm f2/8 macro a useful size.

Hmm, could I rip out the optics?

The optics in the 1.7x AF do the AF
The lens just sits there without adjusting focus at all, and the 1.7x optics are moved to provide focus - I suppose doing focus at the back-end.
You gain 1.7x in focal length, and lose 1.7 f-stops for the privilege.

Other than that, it's a fine piece of Pentax glass and engineering
Matt

In any event it would probably be more cost effective to buy some new AF lenses and sell the MF ones on eBay. Certainly it would be much easier.

Ah right, I presumed something in the converter adjusted the focus of the lens itself somehow.
Thanks.

Thinking about it that would be virtually impossible

Apart from a pull out mechanical pair of "fingers" that came out the adapter to rotate the front focus ring
A job for Don maybe...

As John says, it'll be easier to switch to AF lenses!
Matt

even Don knows when a project is wasting time.....


seriously, though, the IQ of that converter defies conventional wisdom.....
now has anybody tried reverse mounting a lens to that converter or mounting a lens babie?

I think way back in the film days I tried a black body cap, with tinfoil and a pinhole....

Just try out before you buy if you can, and weigh the results against the cost of a new lens