[GeoffKwok]

I'm interested in this lens, and would like who has this lens could share your comments to me.

1) How the quality of this lens? Sharp? Clear?
2) What is APO, EX, RF, and HSM stands for?
3) How much is it?
4) Do I need to buy a converter for Canon camera?
5) How much for Sigma 1.4 and 2.0 extender?

Thanks.

[LifeAfterDeath]

1.)lens is okay...
2.)APO & EX... no idea (All I know EX is a series... which is better then Sigma old type of lens)
RF... rear focus
HSM... same as USM in Canon
3.)less then $6000 (Cixxxxll)
4.)no need
5.)1.4x around $1300
2.0x around $1700
with tele converter... only MF...