Originally posted by MikesChevelle
I am looking at K Mounts on eBay and am running accross a few 2x lens. I am assuming that would turn a 80-200 into a 160-400.
My question is can I use two of those and get a 320-800?
you are talking about teleconverters.
In theory yse you can stack them together and get a 310-800mm lens out of you 80-200,
but even if you have an 80-200 F2.8, it would be a 320-800 F11.
You sould need a ton of light to use it, or gery hiogh ISO
Additionally each TC will degrade the image slightly, so unless you get very very good lenses and TCs, the image quality would be very bad.
Other issues are even if both the lenses and TCs were auto focus, no camera in the world can work with an F11 lens and autofocus. the real limit is about F6.7 whish is why even kit lenses are this fast, and why many TC manufacturers will state clearly a TC will cause loss of AF.