The autofocus technology that exists in the K1 has seen an upgrade from the previous iteration found in the K3 II. The camera gets a new AF module (called SAFOX 12) which features 33 focus points, 25 of which are cross type. The central three of these offer higher precision when used with F2.8 or faster lenses and the central 25 continue to focus down as far as -3EV.

An 86,000-pixel RGB metering sensor acts to offer 77-segment metering but also, hypothetically anyway, aids the camera's autofocus system, enabling scene analysis and subject detection to yield accurate exposures and automatically select the correct AF point to stay on your subject (subject tracking) when using continuous AF.

Seen here are the 33 focus points used in the K-1's autofocus system, 25 of which are cross type. As you can see, the overall focus point coverage area is limited.

Unfortunately, the improvements really don't seem to make that great of a difference in terms of performance as the K-1's autofocus system behaves in much the same manner as the K3 II. Even in the most basic, single point AF shooting modes, the results are far from what we would expect from a modern DSLR focusing system. The autofocus tends to hesitate, even in AF-S mode with the center point - meaning it's not as consistently fast as most Canon and Nikon DSLRs.

This hesitant behavior is more noticeable in AF-C mode, with focus falling behind the subject then having to jump to catch up. Subject tracking - where the camera shifts the AF point automatically to follow your in initial subject if it moves away from the initial AF point - has a very poor hit rate and seems to default back to infinity once focus is lost.

In addition to these limitations the focus points aren't illuminated in the viewfinder until you lock focus, at which point they glow red. This was a bit frustrating when attempting to focus in low lighting conditions. After all, if you don't know where the focus point is before you even initiate focus, how do you place your point over your subject properly? This can be remedied, somewhat, If you press the focus mode button (on the side of the body) while you are focusing. All of the active AF points (1, 9, 25 or 33 depending on your settings) and the entire screen inside the view finder will be illuminated in red. This uncertainty over the selected AF point is made worse by the lack of dedicated AF control to select AF points (you can set the four-way controller to default to AF point control but that's small consolation when you've got the camera to your eye, press it and find you've changed White Balance because you've toggled out of AF point mode).

Moving Subject AF Performance

In circumstances where there is a clear subject, single point continuous autofocus seemed to be the most effective way to utilize the AF system found on the K-1, but even that failed about half of the time during our AF bike test (all images were shot at 200mm using the HD Pentax D FA* 70-200mm f/2.8 ED DC AW lens). Continuous AF with a single point really struggled to maintain focus on an approaching or receding subject - something DSLR AF systems tend to do really well.

During the single point AF bike test seen above the AF would inconsistently lose focus and re-acquire focus sporadically throughout the 14 frames. This was a bit disappointing considering that the AF system used in the K-1 was supposedly an upgrade from the K3 II.

In addition to those issues the subject tracking mode seemed to have a great deal of trouble with even the slightest amount of movement. In our test designed to simulate a subject moving unpredictably at a moderate speed (such as a small child running towards the camera) the subject tracking failed nearly 85% of the time with limited attempts to reacquire the subject after losing focus.

We attempted this test utilizing two different parameters (and a variety of AF hold settings). The first method we tried involved manually specifying an initial AF point to define our subject (the cyclist), the second utilized the K-1’s ‘Auto’ mode where the camera initially determines the subject. We saw little to no difference between the two settings. It looks as though, if the AF loses subject focus, it falls back to back focusing and hunting with limited attempts at re-acquisition.

The subject tracking really struggled to lock focus and failed to reacquire once focus was lost during our 'bike-weave' test. We also noticed that the AF system was subject to focusing at infinity when the tracking system lost subject focus.

The final point of frustration came when we reviewed the K-1's images. Once you have taken your exposure, viewing the image to check for sharpness is a bit cumbersome as there isn't a dedicated one-button method to zoom in on your point of focus. Most modern ILCs offer this, so it's an unfortunate omission.

Low-Light AF Performance

ISO 12800 at 1/320 sec F2. Edited to taste in ACR. This image was shot using the Sigma 35mm F1.4 Art lens. I also spent a bit of time shooting with the Pentax 77mm F1.8. Photo by Dan Bracaglia

The K-1 is capable of focusing in very dark situtaions, that much is certain. However, actual acquisition speeds in dark and low contrast shooting scenarios can be sluggish, though the camera does eventually achieve focus. This is assuming you are using one of the 25 central points. When shooting live music with the camera set to prioritize focus over release (which is its default setting), I often found the camera's AF acquisition speeds in AF-S too slow to keep up with the movement of the subjects, or to nail the decisive moment as soon as it happened. Somewhat counter-intuitively, I had better luck switching the camera to AF-C, which by default automatically picks whether to prioritize focus or release depending on the shooting scenario. In AF-C, the camera struck a better balance of getting near focus and just taking the shot, rather than adjusting focus over and over again, as it tends to do in low light in AF-S. You can work around this conservative AF-S behavior to an extent by setting the camera to release-priority, but that swings the balance to the opposite side: the camera will fire the shutter even if the subject is completely out-of-focus. Meaning you'll have to pay close attention to when it appears that focus is achieved through the viewfinder before fully depressing the shutter.

Meaning, somewhat counterintuitively, we almost recommend you switch the camera to AF-C in very low light. Pentax is in fact to be commended for continuing to focus in AF-C in very low light: many Canon systems only exhibit their -3 EV focus capabilities in AF-S, resorting to hunting more easily in AF-C in such dim conditions. Nikons behave more like the Pentax - continuing to focus in low light regardless of the AF-S/C setting.

I also ran into serious frustration when I realized the AF points do not illuminate until focus is confirmed. This is incredibly problematic when shooting in a dark environment unless you leave the focus point dead center. Even then, it's problematic, as one needs to be able to see the point in order to place it over the subject! Because of this, every time I looked through the viewfinder I was forced to move the AF point around using the directional pad simply so I could see what area of the frame I'd left it in. Doing this momentarily delayed me and occasionally caused me to miss a shot. This can be remedied by pressing the focus mode button while focusing on your subject- the entire screen will become illuminated in red light, which can make finding the focus point and adjusting it somewhat difficult until your eyes adjust to the light.

Camera companies measure the advertised low light AF sensitivity differently and so as a point of reference we compared the low light extinction point of the Nikon D750 to the Pentax K-1. Both are rated down to -3 EV (though the K-1's extreme off-center points are only rated to -2 EV). We found both cameras able to acquire focus in the same impressively dark controlled scenarios. However the Nikon did so significantly quicker and more reliably, which meant the difference between a focused and missed shot. The reason we looked at it next to the D750 is because it is a class leader in terms of low light AF speed and performance. Even a Canon 6D focused more quickly and confidently in and around -2 to -3 EV (in AF-S).

In short, if you are shooting in low light using AF-S (default settings) the K-1 is often reliably able to acquire precise focus (even on very low contrast subjects), but you may wish to switch the camera to AF-C, or set up AF-S for release-priority, to speed up shutter release. Do note, though, that this can sometimes come at the cost of accuracy, with the camera potentially firing when focused hasn't yet been perfectly achieved.