Replying to White Balance/ Over exposure question

Allright NS,

I was helping my buddy film for his new edit on the glacier, he was fish and I was long. He has the 60d and I have a T2I. When watching his fisheye footage, I noticed it was considerably darker than fisheye footage I had taken in the past, and we both have the Rokinon 8mm. He had his aperture set at the F 3.5 and it was still really dark. He said he sets his white balance using the "wheel" on his 60d and this makes it darker. I was just wondering what he was doin? I set my custom white balance and still had to bump my aperature up to F/13 to get a darker look. He said he has no filters and I don't think he has magic lantern and I'm also shooting at ISO 100 and 250 or 320. I'm just hoping to get less over-exposed video on the glacier without blowing up the aperature too much?