On 2010-09-03 5:22, Boris Liberman wrote:
[...] It can be done with K10D but you cannot just point the camera, compose the image and shoot away hoping that automatics will automate the rest of the process.
"Lock time" can get to be a serious problem as the rate of change of focal distance/point increases, but it's not really an AF problem or a Pentax problem, per se.
For example, when I'm really close to a part of the race track where the cars are crossing my field of view quickly (60 MPH from 20 ft), the actual focus in the captured frame is about one AF point "behind" the action compared to the focus it had when the shutter release closed. If they're moving left to right, I have to shift the selected focus point one to the right to get the actual focus point I want. This happens in all usages.
Basically, the internal computer senses the shutter release button closing, possibly makes a decision on focus and exposure (depending on shooting mode), and fires off signals to the analog and mechanical systems to initiate the exposure. The analogs and mechanicals get their stuff together and do as ordered, and the exposure is captured on the sensor while the shutter is open.
All of this takes time. It's not much time, on the order of a few milliseconds. But it's enough to make a difference if the "velocities" within the image are high enough.
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