teleconverter

See the excellent review below which lists the pitiful handful of Sigma lenses that this teleconverter is compatible with. I wish I'd read it before I ordered it (I had to return it after opening it, the list is only INSIDE the booklet*). I have several wonderful Sigma lenses, but none are on that list, and the ones on that list would duplicate what I have, so I have no intention of bying one of the few lenses this teleconverter could work with. *Also inside the booklet is a warning that trying to use the lens with any lens not on the list may damage both the converter and the lens. Well, yeah, a quick glance shows that they used the standard connecting bayonet at only one end (the camera end) and used some strange lens-specific screw mount at the other end. And the possible reason: My Nikon camera body has plenty of space behind the bayonet mount in case the lens needs to extand back a little, but this teleconverter extends FORWARD beyond its front so only a lens with plenty of space "in front of" the bayonet mount (ie, at the lens' camera end) would be able to mate with this. So it looks like they have to specially design lenses just to be compatible with this odd teleconverter, and that would explain why the list is so short.

This converter not only work only on Sigma Lenses - BUT CERTAIN SIGMA LENSES!

The converter will work in MF mode only, unless noted, on the following APO lenses:
Macro 180mm f3.5 EX IF HSM
300mm F2.8
300mm F2.8 EX HSM (AF)
Tele Macro 300mm F4
Tele Macro 400 F5.6
500mm F4.5
500mm f4.5 EX HSM
800 F5.6
800 F5.6 EX HSM
1000mm F8
50-500mm F4-6.3 EX RF HSM
70-200mm F2.8 EX HSM (AF)
70-210mm F2.8

This has really turned me off from Sigma, as this IMPORTANT information is NOT listed anywhere!

This 2X teleconverter is a great addition to any fast Sigma lens. I use mine with my Sigma 70-200 f/2.8 HSM. It is sharp, well made, and a relative bargain. I recently used it to shoot at Road Atlanta and was very impressed with the results.

Of course, it is not designed to use with Nikon lenses, only Sigma lenses on Nikon bodies! And that job it does very well.