HD Pentax-DA 55-300mm F4-5.8 ED WR Review

Autofocus vs DA* 60-250

After the previous four pages, we've assessed the different image quality characteristics of the HD 55-300 and its professional grade DA* big brother. Until now, however, they were just that - the image quality. On this page, we finally arrive to what is of the most interest to many of you - how the lenses fare during the act of automatically acquiring those images.

Autofocus Testing Methodology and Settings

In many autofocus tests, two lenses (or cameras) are pitted against each other, satisfying the desire for how they react to similar circumstances. But that's just it - the detail of how they are compared often negates the results of the test because they are compared during different iterations.

In order to fix this, we didn't shoot one lens and then the other, but rather both at the same time. The purpose of this is so the movement speed of the subject is no longer a variable -- slight velocity/direction/etc. differences between iterations that would possibly cause the two lenses to react (and thus focus or misfocus) unnecessarily. During our AF tests that will follow, we've made that now a constant since both lenses on the same camera body (we used two Pentax K-3 bodies, one for each lens), with the same settings, are shot simultaneously. Thus, every single iteration of this test only has one variable - the camera handling capability of the camera user, which brings us to how we did it - our reviewer had two friends help out with the execution of these tests.

First, one friend assisted by operating the other camera (and lens). Admittedly, he is not a competent photographer, however he is a very competent duck hunter and skeet/trap shooter, so the concept of moving the camera ("rifle") to track a moving target is second-nature. Additionally, in order to further mitigate any user-error on the behalf of either cameramen, every iteration the camera/lens combinations were switched between the two shooters. 

The second assistant acted as the moving subject. We realized that two of the most common (and inherently different) subjects these lenses would be deployed to shoot at would be athletes running, such as in football (both American and the real kind), track and field, field hockey, lacrosse, etc., and flying birds. For the former, we had him, a very fit athlete, sprint both towards the cameras and parallel to them. For the latter, we didn't have the ability to use trained birds to conduct multiple flybys, so we improvised. This same athlete also happens to be an incredibly talented Frisbee thrower, and we found a flying Frisbee to excellently mimic a bird in flight. So much in fact, we recommend you find an open field and a capable friend to launch the rotating discs if you want to practice your manual tracking technique for birds in flight!

All the camera settings were set on both cameras to the same exact parameters, which are as follows:

The following autofocus settings were also in effect during each test iteration:

(*) EDITORIAL NOTE: yes it should have been set to Focus-Priority, however it was accidentally neglected on both cameras, thus the results of this test are still valid and to be considered under the auspices of a controlled test environment.

In order to further mitigate any other variables that would impede the controlled nature of this test, both cameras were fitted with freshly charged batteries as well as one freshly formatted SanDisk Extreme 16GB UHS-1 SD Card each in the SD1 slot. In combination with these high speed memory cards, the smaller resolution JPG's were selected (as opposed to RAW) so as to remove any issues with the buffer hampering the autofocus processing. In essence, both cameras were 100% identical in every single aspect and without anything to strain their autofocus capabilities except for the lenses.

The only thing that was altered throughout the iterations was the focal length, however both lenses were zoomed to matching focal lengths during different iterations (except the few at max zoom for each lens).

Now that we've covered the technical details, let's see the results.

Comparison One - Running Parallel to the Cameras

To start with, we had our assistant run parallel to the cameras as depicted in the below animated .gif:

The results of in-focus shots are as follows:

Comparison Two - Running Towards the Cameras

For our second test, he was ordered to run in a manner that was directly towards the cameras without slowing down by running through a 1 meter gap between the two shooters.

The lenses fared as such:

Comparison Three - "Flying" Parallel to the Cameras

Next, the two cameramen tracked a Frisbee during its lofty flight in a manner similar to the below depiction:

For this test, the outcome is below:

Comparison Four - "Flying" Towards the Cameras

And in our final test, in much the same manner as the second comparison above where the subject came towards the cameramen, Frisbees were directed right over the heads of the photographers.

For our final autofocus comparison test, these are the tabulated results:

Verdict

After combining all the four tests' results in one consolidated area, this is what we are left with:

It goes without saying that the HD 55-300 won all four tests, with the first test being the closest (a negligible difference) and the other three tests resulting in a 12.9% spread for the next closest match-up.

During these tests, we felt that the HD 55-300 was very snappy, albeit loud as expected, to autofocus whereas the SDM motor of the DA* 60-250 became very taxed. Further away, the DA* seemed to handle the minute focus changes better thanks to its shorter focus throw, and in-lens motor. The much longer focus throw is clearly what caused the most issues for the HD 55-300.

For the DA*'s worst showing, Comparison Test Two, where our assistant sprinted straight towards the cameras, the lens received most of its misses within 5-7m. The lens handled the initial second or two of the series with aplomb, however once he had crossed that threshold, the DA* 60-250 was completely incapable of focusing fast enough, and 100% of the shots within that distance were out of focus. This was consistent across every iteration of that test, and while to a lesser extent, with the Frisbee flying straight at the cameras as well.

Additionally, it was our experience that the HD 55-300 was a bit more inconsistent than the DA* 60-250 when it came to how it missed. The DA* was either dead on or completely out of focus. The HD 55-300, however, had a lot of 'near misses,' which we attribute to a combination of its long focus throw and its slower aperture, which reduced the amount of light to reach the autofocus sensors in the camera. The DA* 60-250 enjoyed greater consistency in its focusing accuracy, and even a bit better focusing speed with a more distant target, however that consistency and close-range focusing ability were severely hindered by its slower SDM in-lens motor.

We'd like to emphasize that the DA* 60-250 shouldn't be dismissed for sports or bird-in-flight photography as a result of these tests. In fact it is still very capable and many of our forum members have produced stunning and professional-quality action shots. But just as much as we'd like to have seen an "HD 55-300 DC WR," we'd love to see the fast DC motor incorporated into the outstanding DA* telezoom. As we've already explored in detail, its optics are nothing short of superb and we feel they deserve better than the SDM motor the DA* 60-250 currently features.

So how well does the HD 55-300 stack against the rest of the competition? We break it down for you on the next page.