Ran IQ tests today using both Canon FD 2x-A and 2x-B Tele-Extenders on various Canon FD primes & zooms. ( on the NEX-7) Canon's "2x-A" extender was designed for use with the Canon FD 300-L and larger. The "2x-B" version was designed for use with Canon FD focal lengths < than 300mm. Both those design intentions were established for film cameras back during film days in the 70's and 80's of course. But I was blown away at the IQ using just the same single 2x-A extender on several primes and zooms...so much so that I got a high percentage of perfect images SOOC that didn't even need any basic post tweaking of my JPEGs...just amazing...obviously the original design intentions don't apply when using a modern digital, or at least the NEX-7. Great to know from personal hands on experience that by just adding a relatively small, lightweight Canon FD 2x-A extender to a bag or backpack...along with something like Canon 28-85/4.0 and 80-200/4.0-L lenses...that I'll have a heck of a range of high IQ focal lengths along on a hike or something.