Sigma 50-150mm differences between versions?


New Member
I am looking for a Sigma 50-150mm lens, but there seem to be different versions.
I wanna use the lens for dslr filmmaking.

1. 50-150 EX DC OS HSM
2. 50-150 II EX DC HSM
3. 50-150 EX DC HSM

I know what the abbrevations of Sigma mean, EX (excellent), DC (digital crop) and so on
So i am wondering what is the difference between number 2 and 3, what is the improvement of version II of 50-150 EX DC HSM instead of the older 50-150 EX DC HSM?

If someone could make that clear i would be very happy