01-21-2012, 05:30 PM
[quote name='Brightcolours' timestamp='1327156669' post='15094']
That means you can't. You have to do a lens movement inbetween. The speed and predictable qualities for phase detect is that you can see it right away.
On the two readings with just contrast detect AF: you can not determine speed. Neither can you with PD-AF. (And the speed has nothing to do with determining the direction of focus anyway, only with tracking focus). Only on paper you can. But in real, you need to know too much, too accurate about the lens in use. So in real, it always is a process of more steps.
[/quote]
C-AF can, of course, detect the object speed. The camera knows the time between two readings and it knows the distance of the object at both readings. The distance information is obviously available - just have a look at the EXIF data (e.g. DxO uses this data to optimize distortions). Consequently it can calculate the speed - that's simple math. If it takes further readings it can even detect acceleration. Additionally C-AF has no problems with RSAs (if it stops down like the NEX 7) - this is an inherent weakness of PD-AF.
That means you can't. You have to do a lens movement inbetween. The speed and predictable qualities for phase detect is that you can see it right away.
On the two readings with just contrast detect AF: you can not determine speed. Neither can you with PD-AF. (And the speed has nothing to do with determining the direction of focus anyway, only with tracking focus). Only on paper you can. But in real, you need to know too much, too accurate about the lens in use. So in real, it always is a process of more steps.
[/quote]
C-AF can, of course, detect the object speed. The camera knows the time between two readings and it knows the distance of the object at both readings. The distance information is obviously available - just have a look at the EXIF data (e.g. DxO uses this data to optimize distortions). Consequently it can calculate the speed - that's simple math. If it takes further readings it can even detect acceleration. Additionally C-AF has no problems with RSAs (if it stops down like the NEX 7) - this is an inherent weakness of PD-AF.