Hi,Sigma is into flourite now? Very interesting.
No, its FLD glass - fluorite equivalent. Its what they use in the 120-300 2.8 Sport, 50 1.4 Art, etc.
I'm curious about what they mean by teleconverter compatibility. Another part of this announcement is the new 1.4x and 2x tc's. Sigma says that this new lens is optimized for them. There is no way the 2x will AF on any body of course, but I wonder if the 1.4 might with f8 focusing bodies. The large 105mm filter size suggests that it may be a "big" 6.3, possibly to enlarge the image circle for better corner sharpness but it could also allow just that bit more light necessary to get reliable f8-ish AF. Or it could be marketing and the TC's are manual focus only. I wonder though because Sigma said specifically that tele's do not work on my 300-800 5.6 zoom and they seem to suggest otherwise with this press release.
Also, this forum is weird. I posted a thread about this in a different sub forum this morning but instead of locking the thread and pointing to this one, they renamed this thread with my title and moved my original post into this thread where it doesn't make sense. That seems like a weird and confusing way of doing things. And there are waaaaay too many sub forums with overlapping topics. Half of them could be merged or deleted and nobody would miss them.
Sigma had been using FLD lens since 2010, so nothing new...
Anyway, about the TC, 1.4x possible, but 2x?? Who's know... may be Sigma got "inside news" that may be the new generation of DSLR will allow AF at F8, F9 and even F11...
Have a nice day.