Pentax K-70 Review

Focusing

While the Pentax K-70’s SAFOX X autofocus system is identical to the one used in the K-S2, the new body does feature one important change: its sensor is the first to incorporate on-sensor phase detection autofocus (PDAF) points, which should in theory give it superior Live View and video AF capabilities. However, the situation isn’t quite that simple.

Below, we’ll take a look at how the camera performs both with traditional autofocus via the viewfinder, and with live view.

Viewfinder Autofocus (PDAF)

The Pentax K-70 inherits its 11-point phase detection SAFOX X autofocus from the Pentax K-5 IIs flagship, dating back to 2012. This particular autofocus module features excellent (even today) low-light focusing capabilities with sensitivity in as little as -3EV of ambient light. This amount of light could be compared to a trail through dim cave or a room illuminated only by a smartphone screen. In other words, it shouldn’t ever fail you in conditions in which you’re actually likely to shoot.

Pentax K-70 Viewfinder AF Points

Nine of the 11 PDAF points are cross-type, and these are laid out in a 3 x 3 grid in the center of the frame. The other two points—less frequently used—are line sensors, positioned to the left and right of the 3 x 3 square. The central AF point is extra-sensitive and can offer increased accuracy with faster lenses.

The Pentax K-70 pulls ahead of competing cameras in terms of low-light autofocus performance. Users of previous-generation Pentax DSLRs (such as the K-50 or K-r) will also enjoy more decisive autofocus performance and faster focusing speeds in low light with the K-70. The improvement in speed is especially apparent when shooting indoors. The overall focusing speed will of course be faster in bright light, but gone are the days of endless hunting in low light.

Pentax K-70 AF with Viewfinder submenu

For those concerned about AF accuracy, it is also worth mentioning that the K-70 supports per-lens AF fine adjustments via the custom function menu.

The viewfinder AF system can be used in either the traditional AF.S (single) or AF.C (continuous) modes, as well as an AF.A auto mode designed for beginners. The former two modes features additional customization settings for focus and release priority. Manual focus is accessed through the AF/MF switch on the side of the camera, or through the same switch on the lens, if available.

There are also a number of AF point modes ("AF Active Area" shown above), including using all 11 points, using the 5 central points, using the center point, selecting a specific point, or prioritizing a single point while giving the camera freedom to "expand" to other points. Regardless of the chosen mode, the camera will only confirm focus using one point at a time. While in AF.C mode, if the current AF point goes out of focus, the camera will first check to see if any of the other points are in focus and only then move the AF motor; this can result in a slight delay at times.

With its 11 AF points, the K-70 lags behind competing mid-range DSLRs such as the Nikon D5500 (39 points) or Canon Rebel T6i (19 points). When also factoring in aforementioned point selection behavior, the Pentax has a disadvantage for shooting moving objects, and its auto-point shooting mode less is robust, though we find the overall performance to still be more than adequate for everything except sports/action shooting.

For the most predictable focusing results with the K-70, we recommend sticking to center point or SEL mode.

Refer to our original SAFOX X overview in the Pentax K-5 II review for detailed speed tests of the same AF module found in the K-S2.

Live View Autofocus (Hybrid CDAF/PDAF)

For the first time in any Pentax DSLR, the K-70 incorporates phase-detect autofocus pixels on the imaging chip, creating a hybrid contrast/phase-detect autofocus system. This sort of focusing has been commonplace in mirrorless cameras and competing DSLRs for some time now, so it’s encouraging to see Pentax finally adopting the technology.

Ricoh's description of Hybrid AF

In short, hybrid AF systems combine the strengths of both PDAF (speed) and CDAF (accuracy) to focus quickly and accurately, without the hunting common to pure CDAF systems. The camera first uses the on-sensor PDAF points to figure out how far the subject is from the lens and get the focus in the right ballpark, then employs the traditional CDAF system to fine-tune the focus.

Unfortunately, Ricoh has confirmed that the K-70 only employs hybrid autofocus during video recording, not during live view stills shooting. We first noticed in field tests that it didn’t seem to be faster or hunt less than the K-S2, so we asked Ricoh representatives about it in an interview. They confirmed that the K-70 only uses its hybrid capabilities for continuous autofocus during video capture.

In practice, the K-70’s non-video live view AF is more or less identical to the K-S2’s. It may be ever so slightly quicker or more sure-footed thanks to incremental improvements between generations, but there is certainly no quantum leap over past performance.

Pentax K-S2 Multi-Point CDAF (identical on K-70)

Still, we had plenty of good things to say about the K-S2’s live view performance, and all of them apply here, if tempered by the disappointment of non-functional hybrid AF.

The default focusing mode uses 15 focus points in a 5x3 grid, and it also allows for face detection within this region. If you switch to multi-point mode in the live view menu, the OK button can be used to adjust the size of the focusing area to 7x5 (the whole grid), 5x5, 3x3, or 1x1.  For best results we recommend using multi-point mode with a 5x3 grid.

AF locked in multi-point mode

One nice feature of the multi-point mode is that the camera does a fairly good job of predicting what you want to focus on. It can even outline your subject by covering it in AF points, as shown above.

AF in SEL mode

If multi-point mode gets it wrong, there is also a SEL mode that allows you to place a small AF area just about anywhere on the screen, as shown above. This mode enables the most precise focusing, but it is more time-consuming to use and the focusing speed will be considerably slower. We recommend this mode in scenarios where sharpness is critical, i.e. when shooting on a tripod.

In addition, the live view AF menu contains a spot focusing mode which is essentially SEL mode with the AF point centered, making it somewhat redundant. Also, if you stumble upon the tracking option in the menu, stay away—it simply does not work as one would expect.

Continuous Autofocus During Video Recording

Thanks to the hybrid AF system, the K-70 is the first Pentax DSLR to offer continuous autofocus during video capture. This feature is only available in conjunction with compatible lenses, including all DC lenses and PLM lenses (i.e. the new DA 55-300mm f/4.5-6.3 ED PLM WR RE).

Wow! AF.C, finally! (Too bad it's no good.)

To engage the AF.C mode in video recording, you need to either bring up the control panel by pressing the INFO button, or go into the video menu and the AF with Live View sub-menu. Continuous autofocus works with the automatic multi-point, SEL, and spot-focusing modes.

We tested this combo in the field and found that while it does indeed focus continuously, it’s not very good at it. Our subject (a fast-moving dog) was out of focus more often than it was in focus, and the system hunted constantly. Autofocus tracking was a miserable experience, and the system would even hunt when trained on a static subject.

While we’re happy to see Ricoh making efforts to improve Pentax’s historically sub-par video options, it’s clear that they still have some way to go to get anywhere near what Canon, Nikon, Panasonic, and Sony can offer.

Faster Screwdrive Motor

If you’re upgrading from a camera more than a couple generations old, the K-70 will also have noticeably faster autofocus with screwdrive lenses thanks to a faster screwdrive motor originally introduced in the K-3.

Compared to earlier models, this motor greatly increases the focusing speed of screwdrive lenses with a long throw, such as telephoto or macro lenses. This applies both to viewfinder shooting and live view, but is especially apparent in live view. We measured up to a 50% improvement when testing the K-3 (the first camera to feature the faster motor). Focusing with standard lenses with a short throw (such as the DA 40mm or 50mm) will also be faster, but not by as large of a margin.

As of this writing, cameras featuring this faster AF motor include the Pentax K-S1, K-S2, K-70, K-3, K-3 II, and K-1. We expect to continue seeing the faster motor in future models.

Manual Focusing Aids

While shooting through the viewfinder in manual focus mode, the K-70 offers AF confirmation. Catch-in-focus is also supported with manual lenses or any lens with an AF/MF switch.

When it comes to precision focusing, however, nothing beats live view. To this end, the K-70 features focus peaking and magnification. When enabled, focus peaking adds white outlines around objects that are in focus. There are unfortunately no customization options for the focus peaking, but it gets the job done. Peaking can be enabled through the main menu or the control panel.

Focus Peaking Off (Lens) and On (Right)

Outside of AF point selection mode, the OK button can be used to magnify the live view image up to the actual sensor resolution. Contrary to popular belief, this feature does not simply enlarge the small VGA image that's shown on the camera's monitor: it actually shows you exactly what the sensor sees. Zooming between 2x and 10x is possible, in increments of 2x. Best of all, magnification can be combined with focus peaking, which makes it perfect for manual focusing or fine-tuning the focus.

Live view magnification

There’s just one tweak we’d like to see made to this mode. Currently, if you engage the autofocus while the view is magnified, it will snap back to showing the standard live view image. It would be nice to keep the image enlarged to verify that the AF has done its job properly and to fine-tune it more easily. Currently, you have to zoom in manually every time after focusing.

Low-light Shooting and Autofocus

The -3EV capabilities of the K-70's autofocus system work as advertised, and are a blessing if you do a lot of indoor or nighttime photography. In an earlier test of the K-S2’s identical SAFOX X autofocus system, shot inside a cave with a kit lens, no tripod, and no AF assist light. The system passed with flying colors:

ISO 12,800 hand-held sample (from K-S2, to demonstrate SAFOX X focus quality only)

The K-70’s new sensor provides excellent noise performance that’s a perfect match for the improved autofocus system. From a practical point of view, the low-light focusing of the K-70 is one of its biggest improvements over previous mid-range bodies.

Verdict

While it’s disappointing to find that the advertised hybrid live view autofocus doesn’t work with live view stills shooting, the legacy CDAF system is still quite fast and accurate in daylight. Moreover, the K-70’s battle-tested SAFOX X viewfinder autofocus system is good enough for most use cases. It won’t keep up with Canon and Nikon when it comes to shooting sports and action, but for slower-moving subjects and still life/landscapes, it’s more than competent.

Manual focus shooters will appreciate the K-70’s suite of focus aids, including focus peaking and magnification in live view, or focus confirmation and catch in focus in the viewfinder. None of these are new to the K-70, but they work as well here as they did in the K-S2, K-3 II, and other previous models.

Unlike previous Pentax bodies, the K-70 does support continuous autofocus during video recording, when paired with the new 55-300mm PLM lens. Unfortunately, it’s absolutely awful; we wouldn’t recommend using it under any circumstances. You’d be far better served to learn how to pull focus manually.

Ultimately, while the K-70 promises a lot on the AF front, it delivers very little over the K-S2. That said, we were impressed with the K-S2’s overall AF performance, so while the K-70 isn’t a notable step forward, at least it’s not a step back.


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