Pentax has upgraded the autofocus system in the K-5 II and K-5 IIs. We ran a controlled test at three light levels: EV 7, EV 4, and just below EV -1. The test was done indoors in fluorescent lighting comparing the K-5 IIs to the original K-5. The same lens was used on each camera.
The times represent how long it took for each camera to release the shutter after the shutter release button was pressed, in seconds. Each test was performed 7 times and the median value was selected as the final measure of center. The K-5 IIs is an improvement over the old model in sensitivity as well as speed in low light. Overall, it won 13 out of the 18 tests.
The target was 2.5 meters from the camera and the tests were done staring with the lens at its closest focusing distance ("min.") and at infinity.
The test also shows that the AF speed depends highly on the lens being used. This is not a surprise but it does underline that when comparing AF speed between cameras one must always take the lens into account, not just its aperture.
In addition, it shows that the more light is available, the smaller the advantage of the K-5 II's autofocus. This is why in daily shooting, where the ambient light is much higher than EV 7, most shooters will not see a difference between the AF systems in the Pentax K-5 and K-5 II.
Except when the K-5 was unable to focus, we found the precision of the K-5 and K-5 II's autofocus systems to be roughly the same. All photos of our test target were in focus when shot. Faster apertures seemed to generally increase focusing speed in bright light, but didn't influence the camera's ability to lock focus (regardless of lighting conditions).
We used a smc Pentax-FA 50 mm F1.4 lens in natural light for this test (same lens on both cameras). Netiher camera had any AF front/back-focus adjustments dialed in. The images were shot in RAW at ISO 100 and no sharpening was applied.
Click on a thumbnail for the 100% crop image.
|Pentax K-5 IIs||Pentax K-5|
Both cameras focus accurately in natural light. The only difference we note is that the IIs images appear a tad more crisp.
Overall, the autofocus in the Pentax K-5 II feels more decisive than that of the K-5, but this difference does not become noticeable until one is shooting in relatively low light. In the EV -2 and -3 range, however, the K-5 II is hit-or-miss; it does not always focus reliably, whereas at EV -1 it is a different story. Similarly, the K-5 cannot focus at EV -1 (as this is the lower boundary of its specified operating range) and is hit-and-miss around EV 0 and 1.
It should be noted that when the AF assist light was used by the K-5 II (which raised the lighting level to EV4), the K-5 II focused faster than the original K-5. This may well be the biggest improvement that most users will notice.
The nature of this improvement means that the K-5 II will be a viable choice for photographers who shoot dark subjects at a distance, where the AF assist light would be unable to help. An example of where the K-5 II would shine is bird photography at dawn or dusk. Apart from the K-5 II, only high-end Canon and Nikon bodies can focus in such low light. Daytime shooters, however, will not benefit much from the upgrade.
For continuous shooting, while the K-5 II's new select area expansion feature (which essentially lets you prioritize a focus point while allowing the subject to move into other areas before the camera changes the distance to the focused target) is nice to have, we found the difference between the accuracy (number of sharp vs. blurry shots) between the K-5 and K-5 II for moving subjects to be negligible. However, the K-5 II seems to treat hunting (focusing all the way to minimum then back to infinity) as a last resort, the K-5 did so slightly more often during our tests. For action photography and sports, the K-5 II is still a little bit behind the competition, and you won't notice much of an improvement in this respect, if any, compared to its predecessor. It's still a capable camera, but competitors such as the Nikon D7000 or Canon 7D are able to make more AF measurements in less time and shoot at higher sustained framerates.
Finally, we were able to identify what seemed like a bug in the AF algorithm of the Pentax K-5 II. When the camera thinks there is insufficient contrast to make a reading (i.e when focused to minimum range and pointed at something with -3 EV), the camera does not even attempt to focus, whereas the original K-5 at least tries hunting. To remedy this, we had to either move the focusing ring manually, or increase the ambient light. Having the AF assist light on prevents this from happening.
So, what's the bottom line? Pentax promised us an AF system that works when it's dark, and they delivered one. In low light under EV 0, the K-5 II outperforms its predecessor as well as its Canon and Nikon rivals, the 7D and D7000. However, overall, the autofocus in the K-5 II is not the big upgrade that Pentax K-5 users have been waiting for. We think that the next step for Pentax is to add more focus points and implement a more powerful motor (perhaps one that is brushless) in order to make their cameras more versatile in everyday shooting conditions, and for shooting fast moving subjects. The Canon and Nikon bodies excel in these areas compared to the Pentax K-5 II. With that said, for everyday shooting, the AF systems in both the K-5 and K-5 II are more than adequate.
The contrast detect (live view) autofocus in the K-5 II offers the same performance as that of its predecessor. In other words, it is a bit lacking in speed (but not in accuracy), and the Pentax K-30 outperforms it in most cases (see in-depth comparison).
The Pentax K-5 was observed to have AF accuracy problems (front and back focus) when shooting in tunsgten light. The Pentax K-5 II does not have this issue.
The AF point size and layout on the K-5 II is the same as on the original K-5. There are 11 points total, 9 cross-type in a 3x3 matrix, with an additional point to the left and right of the center row of the matrix. The K-5 II's AF system can work with luminous flux of F2.8 as well as F5.6 according to its specifications. As you saw in our tests, the increase in focusing speed and decisiveness was only significant in low light.