Hi guys,i just got myself a secondhand 1ds MK 11,I am looking at lenses to go with,I am looking at the Canon 24-70 l 2.8.i am also looking at the 70 200m 2.8.Can anyone tell me what the Other options,ie sigma equivalents to these 2 lenses.Is there that much of a difference in them in your opinion,thanks guys.Also will the sigma equivalent work with a canon converter which i also have,