All the discussion in this forum about the 5D3 in low light has me intrigued. I'm particularly interested in a 5D3 w/24-105 f4L IS as an upgrade path for a 7D w/17-55 f2.8 IS. (For low light candids, I'm often shooting at 1/30 second and find IS to be a must.)
I know that the 5D3 offers greater color depth and that full frame is typically sharper than crop. I also understand that the 5D3 offers about a 1.3 stop advantage in noise over the 7D. But, I'm comparing a crop body with a 2.8 lens to the full frame with a 4.0 lens and this noise advantage drops to about 1/3 of a stop.
Now the question. A 2.8 lens lets in more light than a 4.0, which is more light for the AF system to lock in. So which system can lock in on focus at lower light -- the 5D3 w/24-105 f4L IS or the 7D w/17-55 f2.8L IS?
I know that the 5D3 offers greater color depth and that full frame is typically sharper than crop. I also understand that the 5D3 offers about a 1.3 stop advantage in noise over the 7D. But, I'm comparing a crop body with a 2.8 lens to the full frame with a 4.0 lens and this noise advantage drops to about 1/3 of a stop.
Now the question. A 2.8 lens lets in more light than a 4.0, which is more light for the AF system to lock in. So which system can lock in on focus at lower light -- the 5D3 w/24-105 f4L IS or the 7D w/17-55 f2.8L IS?