In article <32D58746.5355@ids.net>, mecastor@ids.net says...

>I was wondering what the best (clearest) 2x teleconverter is. Any help
>is welcome.

The 7-element-types made for shorter-type lenses are barely
useable with the lens wide open, are sometimes acceptable by
f5.6 (depends on the lens), and can be good at smaller stops
(which, with the 2-stop speed loss, makes them generally
useless for anything but flash macro work). The expensive
camera-brand 2X converters intended for long-lens use
only can be excellent when combined with the expensive
camera-brand teles, especially if used at f5.6 and smaller
stops.
Hope This Helps