Hello
Your Sigma is about 26-27cm long - as I don't know which cam is attached and how thick it is:
https://www.lowepro.com/global...
The backpack is 42 cm long and high inside, so it should fit.
LG

I do hope that Lowepro has improved the second version of this backpack. The first version was lousy to wear and you felt every piece of equipment in your back. But for the price, you can't expect more. It's cheap mass-produced goods. I always recommend the Shimoda backpacks. Expensive but worth every franc.