Jupiter-9, which Teleconverter?

[systemA]

Hey there folks.

I am looking for a teleconverer for my Jupiter-9 M42 lens and a k10d. I currently use a M42 -> kmount adapter to attach the lens. I just have a few questions:

1.) Do I need a M42 -> k-mount teleconverter? Could/should I use a k-mount to k-mount teleconverter?
2.) Will I lose any functionality by using a teleconverter? If so, is there any way to change this?
3.) Optically, how much does a teleconverter affect IQ? What is the economical choice for a 1.4x or 2x?
4.) Say, if I'd like to get a teleconverter that would also work with my FA 50mm/1.4 and keep all functionality, which one should I go for?

Thank you for the help, sorry for not knowing anything about teleconverters.

[Igilligan]

But if you are looking for one that you can use on the jupiter and the FA 50 then you are going to want a K mount with AF and A metering like the Tamron 1.4x or one of the others that does AF. You will not have any AF or A with the jupiter obviously only green button metering. Put the m42 to k on the lens and put the that combo on the tc.

It will work with the FA 50 with full functionality only a little slower.

I think it might have been Hin who did some tests on some tc's... do a search for tc comparisons.

I will try and shoot a few tomorrow with my tamron 1.4 and the jupiter if that would be of some help...