Lens converters (screw on, 2x)

[videogamemaker]

Can someone tell me more about these? The only two I've seen that seem nice are the Nikon TC-e2, and the tiffen 2x. Both seem more for smaller lens cameras.
Have there been many conversion lenses in the past?
Were there any for the Hexar AF? 35 is mighty convenient, but having a small pouch with a 2x would let you get some good closeup portraits as well.

Why do they seem like such a good idea, and (at least the nikon and tiffen ones) offer reasonable quality, not softening too much, yet seem to exist in so few. I've tried googling, but mostly it comes up with the kind that go on a dslr first, then the lens attaching.

 

[Sonnar Brian]

"Auxiliary lenses" have been around for a long time, typically for fixed lens rangefinders. They were a pain to use, you had to refocus the lens. With SLR's and cameras that use through the lens autofocus, not hard to use- the camera will figure it out. The Polaroid SX-70 Sonar has a 1.5x Telephoto available that incorporated a mechansim that pushed a switch on the camera to recalibrate the Sonar mechanism with the Telephoto installed. NEVER put a Polaroid Aux telephoto on an SLR680 or SLR690: it will break the camera.

 

[videogamemaker]

Thanks for the info. Do you know if there have ever been any 2x lenses that work for wider angle lenses? The ones I have seen all seem to only work on zoom lenses and have heavy vignetting when the lens is set to wide.

Searching for "auxillary" lens on google has found a few new results though, so thanks for that info.