I.Q. Loss With Pentax Teleconverters?

[baltochef920]

I'm interested in the possibility of using either the A1.4x-L or the A2x-L teleconverters with lenses not designed for use with these 2 converters..

I understand that if an extension tube of sufficient length is installed onto the lens first, then these converters will work..

I was wondering if any members had tried this, & what their results might have been??..

How much loss of I.Q. results when doing this..

Also, can anyone tell me how much the front element of these converters projects forward of the teleconverter's body??..

Thanks, Bruce