Originally posted by biz-engineer It's interesting, no I'm not using center point in AFC but I always had the impression that the AFC was always behind the target.
How do you define "predictive AF"? To me "predictive" means that depending on the velocity of the target the AF does not wait for the target to be out of focus to readjust the focus.
I mean that if you consider a PID (Proportinal, Integral, Derivative) controller, I believe that Pentax AF controller only uses a proportional section, whereas the 7D does calculate the next focus base on previous speed of target (from the derivative value), and so is able to reactuate the lens focus position based on next predicted position of target.
Yep that's pretty much what I'd define as predictive. If you think about it all AF slr type cameras have to have some predictive capability else you could never take a sharp image of a moving target.
During the blackout period no AF data is coming to the camera , If the camera did not continue focusing the Target would be ooF by the time the shutter opened.
Sequence must be
1 focusing - > shutter pressed
2 mirror lifts -> camera predicts target location and focuses
3 Focus stops shutter opens
And in the case of AF-c repeat
Where Pentax falls down compared with other is in what Nikon call 3D focusing which is simply predictive in the x,y and z axis . Pentax is weak on the Z Axis though now they have the technology hardware in place (86k exposure sensor) to accurately detect front-back movement they just need algorithms and processing power to match.
You need obliviously accurate front back data for that you need to 'see' size increase/decrease (many acquisition points)
Algorithms to no what to-do with the data
and fast CPU so you can re-assess movement for erratic trajectories.