Originally posted by garyk try another system to see if it is better.
An expensive experiment!
The two systems are hard to compare on the basis of their simple AF specs - eg:
7D
• 19 cross-type AF points (f/2.8 at centre)
• Center point additionally sensitive with lenses of F2.8 or faster
• AF working range: -0.5 - 18 EV (at 23°C, ISO 100)
K-5
• 11-point TTL Phase Difference detection sensor (SAFOX IX+)*
• Center 9-points are sensitive to both horiz and vert. detail
• AF working range: -1 to 18 EV (at ISO 100, F1.4 lens)
On the basis of these specs a K-5's AF should work in slightly lower light than the 7D's. The K-5's EV sensitivity even looks a lot like the current camera AF king, the Nikon D3s:
• 51 focus points (15 cross-type sensors)
• Multi-CAM 3500FX
• AF working range: -1 to +19 EV (ISO 100, normal temperature)
Even the old faithful K-x's AF (on paper) looks more sensitive than the 7D in low-light:
• 11-point wide autofocus system (SAFOX VIII)*
• TTL Phase matching
• AF working range: -1 to 18 EV (at ISO 100, F1.4 lens)
Be keen to see how you go.