Vivitar 2x macro focusing teleconverter: Auto aperture

I have a Vivitar 2x macro focusing teleconverter that I used to use very successfully on my Pentax MX.

I have been trying this converter with my K10D and a Pentax-A 50mm lens, but cannot get the camera to recognise the auto aperture position on the lens. With the lens on is own the camera recognises the auto position.

I am suspicious that the aperture indicating lever within the teleconverter may not manufactured to move far enough to indicate to the camera that it is in the auto position.

Has anyone got any experience of this teleconverter, or any ideas please?

Cheers Rob

Does the converter have the electrical contacts to transmit the information?

The converter does not have any electrical contacts, however neither does the Pentax-A 50mm.

I am assuming that the Pentax-A tells the camera that it is in Auto aperture by moving the aperture indicating lever.

Cheers Rob

Looking at the back of the lens, just clockwise from the recess for the locking pin there is a small protruding ball. I've always thought this was the contact for the "A" setting.

The A series lenses have contacts, but not as many as the later lenses as all they do is allow the camera body to set and read back the aperture selected.

Just to confuse the issue - my Vivitar 2x macro teleconvertor has what looks like a set of 7 contacts, but I haven't managed to persuade it to transfer any information to/from any of my lenses yet ???

I have one and it transmits data fine .. there is a thread somewhere on the other Pentax forum that explains how to fix this (fairly common) problem.

There is indeed a small ball on the Pentax-A just round from the locking recess: this is flush at all apertures and then pops out on the "A" setting.

My teleconverter does not have a "protruding ball". Neither the lens nor the teleconverter have electrical contacts.

Thanks for all the input!

Can anyone confirm that the "protruding ball" is in fact an electrical contact.

Here you go.


If you want to read more about it http://kmp.bdimitrov.de/technology/K-mount/Ka.html

I'd be interested to know why those electrical contacts are used in Tv and P modes, but not in others.

Presumably because to use Av mode on A series cameras and lenses you pressed the A button and then set the aperture on the lens (while the body read this in the same way as it did with K and M lenses).

Yes Like Matt said you just use the aperture ring for Av mode.
The contacts are used to give the camera information about the widest and narrowest diaphragm and that's the info needed for Tv or P mode.

Makes sense?

Having read what DM said It does make sense.

(As an aside, I work with DM and Pennfold.:mrgreen

Thanks for the prod - I just followed the instructions here, took the whole thing apart, didn't have any little springs going "boing....weeee...carpet...lost!" incidents (for once!) - and although there didn't seem anything wrong, once I put it back together, it now works in Av Mode - hurrah!

The bad news is that I was misled by the labelling - its a "2x MC TC" NOT a "2x Macro TC" - so only works as a Teleconvertor (i.e. next-to-useless), not as a Macro (useful). I would be annoyed, because I only wanted it for macro sillyness, but it cost a fiver off Ebay, so...meh!