Autofocus
On paper, the 19-point AF system of the Canon EOS 7D beats the 11-point system of the Pentax K-7. As well as having fewer points, the Pentax model is less versatile and neither the point selection method nor the AF response time can be varied to suit the subject.
However, in most circumstances the Pentax AF system performs well and pulls the subject quickly into focus provided there is reasonable light and subject contrast. It’s only really when the light is less than perfect that the K-7’s AF system starts to falter and the outer AF points become prone to indecision. Although no autofocus system is infallible, the Canon AF system in the EOS 7D performs significantly better than the K-7’s in low light.
Pentax lenses such as the smc DA 18-55mm f/3.5-5.6 AL WR, which is weatherproofed and the ideal kit lens for the K-7, like to let you know that the AF system is doing its job.
Focusing is accompanied by a familiar ‘zzz-zzz’ sound that can make it seem as if it is struggling to focus more than it is. It is perfectly adequate for general photography, but if I were planning to shoot sport I would opt to use the EOS 7D because of its superior AF ability.
Landscape, still-life and macro photographers who compose images on the LCD screen will find little to distinguish the two contrast-detection Live View AF systems. But given that both cameras provide a decent magnified view of any part of the scene, manual focus is a much more sensible option for these users.
The fact that the K-7 can only autofocus prior to recording video footage while the EOS 7D can focus during recording isn’t a significant disadvantage. Like many contrast-detection AF systems, the EOS 7D’s is prone to drifting around the subject before homing in on it, and this looks terrible in a movie.
