Pentax-DA 560mm F5.6 ED AW
Shown above is the scene we used for the autofocus test. The camera is our K-5 IIs with the latest firmware which improved support for the DA 560mm autofocus in live view. The subject to focus on is the center of the crown of the palm tree, 55 meters (180 ft) away:
|F5.6 - PDAF|
We tested phase detect autofocus (through the viewfinder) as well as contrast detect autofocus (in live view mode).
We focused the lens past infinity as far as it would go and ran the test. We then focused at 15m (49 ft) and ran that test. We also focused at about 5 meters off target and ran the test. The focus limiter was engaged but the lens never hunted so the limiter didn't play a role.
Here are the results:
The DA 560 mm features the Quick-shift function which allows you to fine tune focus manually by turning the focusing ring after autofocus has completed. We found autofocus very accurate and did not have to resort to Quick-shift.
|AF accuracy, no sharpening applied - F5.6 - click image for 100% crop|
|AF accuracy, slight sharpening applied - F8 - click image for 100% crop|
The lens uses internal focusing which means that less mass has to be moved during focusing and that the lens doesn't extend when focusing closer.
The DA 560 mm has an amply-sixed focusing ring and a long focus throw (note the distance between the 6 and 7m marks) for an autofocus lens. This makes manual focusing easier and even though the maximum aperture is a relatively dark F5.6, we found manual focusing in the center of the frame quite possible in the field. Achieving accurate focus manually on something near the edge like our test chart was more difficult and we got better results using autofocus in live view and moving the focusing area out to the edge.
Here is a manually focused shot of the moon - note that the focusing ring goes past infinity so you actually do have to focus on the moon! Click image for a 100% crop (400 kB):
The green fringing on the right hand side indicates that focus is slightly off. Compare this image with the AF version shown earlier and you will see that AF is spot on - almost no green fringe.
Verdict on Autofocus
We were impressed with the accuracy of phase detect autofocus on our K-5 IIs. Contrast detect autofocus is also very accurate, but phase detect in many cases bettered contrast detect.
We would deem the autofocus speed average with phase detect being the faster method. When shooting moving wild life it can be recommended to pre-focus the lens near the subject to avoid a long travel of the focusing mechanism during which time the subject may have moved out of the frame! Contrast detect can only be recommended for stationary objects due to the slower speed.
If you are used to the focusing speed of a short lens like the DA 18-135 them you must be prepared that the DA 560mm is slower and hence more difficult to work with for moving subjects.