Pentax K-1 Review

Focusing

Rather than reusing an existing Pentax AF system, the K-1 debuts SAFOX 12, Pentax's newest phase detection autofocus system.  In addition to this, the K-1 has a variety of secondary AF facilities and focusing aides which we will discuss and analyze in detail.

Viewfinder Autofocus

SAFOX 12 builds on SAFOX 11 in two key ways.  Most importantly, thanks to the LCD overlay in the viewfinder, the new system is able to provide better feedback to the photographer.  Multiple in-focus AF points can now be illuminated at once, so it is often possible to clearly identify which object(s) the system has decided to focus on.

To illustrate how this works, we took a photo of what's shown in the viewfinder when the AF is activated in Auto mode.  Notice how the four AF points clearly follow the edge of the brochure:

The camera clearly shows the photographer what it's focusing on

The other key improvement is that compared to the K-3's SAFOX 11, three additional line-type AF points have been added on either side of the central 5x5 cross-type point grid, thereby increasing the total number of AF points to 33.  We would have liked it if the new points were cross-type, though, as this would have given the K-1 even better accuracy throughout the AF grid.

Still, these extra points seal the gap that previously existed between the central grid and the rightmost/leftmost points.  This is beneficial for tracking and allows larger offsets in SEL and A-9 mode (we discuss AF point modes in more detail in the following section).

K-1 33-point AF layout (25 cross-type in the center)

As on the K-3, the center point and the two points directly above/below it are able to take better advantage of faster lenses (up to F2.8).   The center point is slightly larger than the other points, with the exception of the two most extreme line sensors.

The area covered by AF points is unchanged on the K-1 compared to Pentax's crop bodies.  AF points span just over half of the APS-C image area.  More coverage would be desirable, but we didn't find the size of this area to be a major limitation (unlike on the 645Z, where the large size of the viewfinder dwarfs the AF system).

PDAF Options and Modes

The Pentax K-1 introduces a consolidated page in the main menu which contains all viewfinder autofocus options.  The first two settings can also be accessed via the Control Panel as well as while pressing the AF MODE button near the lens mount.  The latter is especially useful, as the AF Mode and AF Active Area can be changed without looking away from the viewfinder.

Switching between autofocus and manual focus is controlled exclusively via the physical AF/MF switch on the camera or via the AF/MF switch found on select high-end lenses.

Phase detection (viewfinder) autofocus menu

Let's take a quick look at the configurable settings:

  • AF Mode

    AF.S
    The AF will operate a single time for every half-press or AF button press

    AF.C
    The AF will operate continuously while the half-press/AF button is held down

  • AF Active area

    Auto-33
    All 33 points are used and the camera automatically tries to identify the subject

    Auto-9
    9 user-selected points are used (any 3x3 grid within the AF area) and the camera automatically tries to identify the subject

    Spot
    The central AF point is used exclusively

    SEL
    A single use-selected point is used exclusively

    SEL-S (AF.C only)
    The user selects a single AF point for priority focus, but the system will use any adjacent AF point (up to 8 neighbors total) to track the subject if it leaves the priority area

    SEL-M (AF.C only)
    The user selects a single AF point for priority focus, but the system will use any adjacent AF point, or any neighbor of an adjacent point, to track the subject if it leaves the priority area (up to 24 neighbors total)

    SEL-L (AF.C only)
    The user selects a single AF point for priority focus, but the system can use any other AF point to track the subject if it leaves the priority area

Note that SEL, SEL-S, SEL-M, and SEL-L are identified as SEL-1, SEL-2, SEL-3, and SEL-4, respectively, on the top LCD and in the viewfinder.  The last three are only accessible during continuous autofocus (AF.C).

In essence, the latter 3 SEL modes are how Pentax implements tracking.  The user has the ability to hint at the location of the subject, but the camera will ultimately utilize other AF points— or possibly the entire AF area— to track the subject.

During our field testing, we obtained the best tracking results in SEL-S and SEL-M mode.  For action shooting, we strongly recommend the use of these modes in lieu of SEL, Spot, or A-9, as they allow the user to combine his/her expertise with the power of the camera's AF sensor to deliver optimal results.

For stationary subjects we really liked the A-9 mode, though an A-5 mode, which the K-1 lacks, would be a welcome supplement for more precise control.  Users of Nikon systems would find this analogous to the Group AF function.  While the "old school" approach of only using a single AF point is often appropriate for ultimate precision, the partially automated mode can really come in handy when things happen quickly (i.e. when shooting weddings or events).

While it almost goes without saying these days, the K-1 delivered exceptional AF accuracy, and virtually none of our over 5,000 (non-action) test photos proved to be mis-focused.  For portrait photography, we made extensive use of SEL mode with great results.

Let's continue walking through the remaining settings:

  • AF.S Setting

    Focus Priority

    The shutter will not fire unless the subject is in focus.  Required for catch-in-focus functionality.

    Release Priority

    The shutter will fire even if the subject is not in focus.

  • 1st Frame Action in AF.C

    These settings can be used to ensure that the first frame in a burst is always in focus.

    Auto

    The camera decides automatically based on how far out of focus the subject is.

    Focus Priority

    Same as above.

    Release Priority

    Same as above.

  • Action in AF.C Cont

    These settings all affect the AF behavior during a continuous burst and have the same effect as described above.

    Auto

    Focus Priority

    FPS-Priority

  • Hold AF Status

    When set to "Off", the camera will instantly attempt to re-acquire focus when the subject leaves the AF area.  Higher settings will delay this behavior.  We recommend "Off" or "Low" unless the subject's motion is easily predictable.

    Off, Low, Medium, High

These supplemental settings can help the user customize the AF system to his/her liking.  We generally recommend using focus priority in AF.S and the first frame of AF.C, though the new Auto setting in AF.C is intriguing and could potentially lead to an optimized balance between frame rate and AF adjustments.  Since the Pentax K-1's base frame rate is not as high as that of the K-3, the setting should not have as big of an impact of the resulting frame rate, as the camera naturally has more time to make AF tweaks in between photos.

While it is impossible to conduct field tests in anticipation of every possible real-life use case, our experience with the K-1 suggests that its AF system is the most effective that Pentax has released to date, in part thanks to the new viewfinder display, but also due to faster overall operation.  Users should thus expect a high "keeper rate" with this camera, should they choose to use it for action. The "Real-Time Scene Analysis System" which Pentax promised in the press release seems to be a little bit more than just marketing speak.  Still, the camera isn't quite as responsive as the Canon and Nikon bodies we've handled recently, such as the 5D Mark III or D810.  Combined with slightly slower AF motors (on average), this puts the Pentax at a disadvantage from a hardware perspective.

Live View

In live view, the Pentax K-1 implements contrast detection autofocus (CDAF) that essentially works through an optimized form of trial-and-error.  It is therefore generally seen as more accurate than PDAF, though this is not always the case in practice, as we will soon discuss. 

Regardless, CDAF is never subject to front- or back-focus.  In PDAF mode, the K-1 otherwise stores either a global adjustment, or up to 20 fine adjustments for individual lenses.  The adjustments do not account for varying focal lengths of zooms.  These settings can be accessed via the C25 Custom Function.

K-1 in CDAF auto mode: 3 points reporting in focus

Contrast detection AF offers a number of modes, and as with the viewfinder autofocus, the first two settings can be adjusted through the Control Panel as well as the main menu.  A focus and release priority setting is new to the K-1, though CDAF almost never fails to lock focus.

CDAF menu settings

The K-1 offers the same CDAF modes as previous Pentax models including the default auto mode with face detection, "tracking", multi-point auto, select, or spot.  Please refer to our K-3 review for a summary of these modes, as they are identical on the K-1.

For everyday shooting, we recommend the face detection or auto mode, as these modes work with a user-selectable AF area and are much faster than the select or spot modes.  In terms of speed and accuracy, we found the K-1 to perform identically to the Pentax K-3.  CDAF speed is generally quite good, though it does slow down considerably in low light or with lenses that have a long focus throw.  Despite the existence of a rudimentary "tracking" mode, Pentax CDAF is usually not appropriate for tracking moving subjects since it needs to turn the AF motor back and forth even if the camera is already close to being in focus.

Selectable AF areas in auto mode (3 others not pictured)

For the best accuracy, select mode is of course the go-to solution as it allows for a nearly stepless placement of an even smaller AF point.

Precise AF point selection in select mode

A minor drawback of focusing in this mode is that it cannot be used on a zoomed-in image, and so the CDAF is limited to the precision shown in the screenshot above.  Attempting to operate the AF while zoomed in will simply reset the zoom.  In comparison, Nikon cameras can focus more accurately on a zoomed in image than the standard live view image.  As a consequence, with the K-1, the best focusing precision can only be obtained manually while the live view image is magnified.  We highly recommend fine-tuning the focus manually using the zoom feature in situations where focus is critical.

In the future, we would also like to see the addition of PDAF sensors to live view for feasible tracking and everyday faster overall performance.  Still, for a pure CDAF system, the K-1's live view autofocus works well for everyday hand-held shooting— far better than Nikon's current implementation, for example.  CDAF feels just as fast as viewfinder PDAF with wide-angle lenses.

Manual Focusing

The K-1 has a number of features to assist the photographer while focusing manually.

Viewfinder

First and foremost, the larger full-frame viewfinder is a boon for manual focusing.  Beyond this, the K-1 supports AF confirmation even for completely manual lenses.  When the subject enters focus, the camera will beep (if sound is enabled) and illuminate the in-focus hexagon in the viewfinder.  With manual lenses, AF confirmation is limited to the center AF point, while AF lenses support all AF points.

The viewfinder is generally bright, though it is of course easier to manually focus with wide-aperture lenses.

Catch-in-focus

A very useful extension of the focus confirmation system is Pentax's catch-in-focus.  With the C24 custom function set, in AF.S focus priority mode, and with a manual focus lens (or an AF lens set to MF via an on-lens AF/MF switch) the camera can be set to fire the shutter only when the subject enters focus.  This feature enables a number of effective shooting techniques with manual lenses, most notably for bird photography or other moving objects.   Learn more about how to activate and use catch-in-focus in our in-depth guide.

Live View

We've saved the best for last.  While viewfinder shooting is the traditional approach that many film-era photographers have become accustomed to, live view is in fact a much more effective tool for precise manual focusing.

The K-1 offers focus peaking, which is a system that highlights sharp edges in the frame.  Thanks to focus peaking, it's very easy to see what objects are in focus, as well as to gauge the depth of field (when applicable).  Focus peaking can be enabled through the Control Panel or through the CDAF menu.  It's an effective tool for hand-held shooting.

The color or appearance of focus peaking outlines cannot be customized.  Objects that are considered in-focus are highlighted in white.

Focus Peaking Off Focus Peaking On

A second useful tool is live view zoom.  The K-1 allows you to zoom in on any part of the image up to a magnification of 16x (100% equates to roughly 10x) so that you can very precisely fine-tune the focus setting.  This is especially useful when shooting on a tripod, and with its smooth live view frame rate, the camera never slows you down.

Magic happens when you combine live view zoom with focus peaking, as this makes it even easier to locate critical focus, in particular with lenses that have a shallow depth of field.

Our only gripe is that the magnification is reset every time you take a photo.

AF Speed

Autofocus speed has always been a hot issue in the Pentax world, in particular because Pentax cameras have the reputation of being slower than their competitors.  In common scenarios, these days this is a myth, although we can't deny that other systems can be faster for applications such as sports photography.

http://www.pentaxforums.com/content/uploads/files/1/1609/PENTAX-K1-SAFFOX-SENSOR-400x300.jpgSAFOX 12 Chip

To get a sense of the Pentax K-1's overall AF speed, we squared it off against the previous-generation Pentax K-3.  We used the same D FA 28-105mm lens (set to 28mm) on both cameras and repeatedly focused it on a nearby test target (black/white checker pattern) placed at a distance of 200cm.  Across two sets of trials, the initial focus was set to both infinity and minimum.  Since this lens has an internal motor, this test allowed us to focus on the performance of the cameras themselves.

We varied the ambient light level and repeated each test seven times.  To eliminate measurement errors, we used an audio recording to obtain our timings.  Of course, we also disabled the AF assist light.  The table below reports the results from infinity.

0 EV (dark) 3 EV (dim) 7 EV (moderate)
K-1 (SAFOX 12) 0.8s (0.4-1.3s) 0.6s (0.5-0.8s) 0.2s (0.1-0.3s)
K-3 (SAFOX 11) 1.2s (0.9-2.1s) 0.5s (0.4-0.9s) 0.4s (0.3-0.4s)

AF speed test: Median time to lock focus after 7 trials (range of all results in parentheses)
w/ D FA 28-105mm @ 28mm (F3.5), focused from infinity to 2m

While we could reasonably conclude that overall the K-1 focuses more quickly that the K-3, the main thing to take away from these results is that Pentax engineers have clearly made tweaks to the manner in which the SAFOX 12 focuses.  The fact that the K-3 yielded a slightly faster median focusing time at 3 EV (albeit also a slower worst-case result) suggests that it uses a slightly different algorithm than its newer cousin, and while the K-1 almost always won, the K-3 sometimes bested it.

We observed that after each "slow" focusing attempt, the subsequent attempt from each camera was much faster.  It's possible that Pentax's current AF implementation considers the last location of the subject during its calculations, even in AF.S mode. 

Another observation is that focusing speed improves dramatically as ambient light levels increase.  Since the lens we used boasts a very short focus throw, this test was primarily an exercise in how quickly each camera could carry out computations and test its micro-adjustments.  The dramatic improvement at 0 EV is a clear indicator of the K-1's ability to perform measurements more expeditiously.

Neither camera ever failed to lock focus in any of these tests, though when we attempted a similar test at -1 EV, misses were intermittent.  Formally, both cameras are rated for AF sensitivity in as little as -3 EV, though performance in conditions this dark is spotty at best without the AF assist light.

We are not reporting the numbers from minimum focus as they are the outcome was consistent with the results above (even at 3 EV).

Moving Subjects

What about performance in the field?  When we photographing subjects like cars or bicycles passing by the camera in SEL-S, SEL-M, and A-9 mode, our subjective impression is that the K-1 carries over the aforementioned improvements to its AF.C mode.  SAFOX 12 is very responsive, especially with the AF Hold setting disabled.  We anticipate that user reports will be consistent with our findings, though we certainly plan to investigate continuous shooting performance in more detail in a separate article.

Screwdrive Performance

We tested the K-1's screwdrive motor speed by starting the lens at infinity and forcing it to focus on a subject placed just ahead of the minimum focusing distance.  We found that the K-1's screwdrive motor is no faster than that of the K-3, though overall AF performance seemed better thanks to algorithmic improvements.

3 EV
K-1 (SAFOX 12) 0.6s (0.5-0.7)
K-3 (SAFOX 11) 0.7s (0.6-0.9)

Median time to lock focus from infinity to a subject at minimium focus
FA* 80-200mm @ 150mm (F2.8)

As before, these results are based on seven trials measured using audio analysis.

Screwdrive Sound

While the K-1's screwdrive motor isn't faster than the already-improved motor in the K-3, it is quieter.  Ultimately, the K-1 boasts the quietest screwdrive operation of any Pentax DSLR we've tested to date.

Pentax DC Autofocus Motors

We've concluded that the new Pentax AF system focuses very quickly, but what about the latest Pentax in-lens motors?

To find out, we compared the latest Pentax D FA* 70-200mm lens on a Pentax K-1 to the Nikkor 70-200mm VR II on a Nikon D810 in bright daylight (13 EV).

It turns out that the Nikon combination still holds a noticeable advantage, but the absolute difference is only a fraction of a second.

Verdict

The SAFOX 12 viewfinder AF system represents another step forward for Pentax.  Thanks to the viewfinder LCD overlay, the photographer gets much better feedback from the camera and can make better sense of the various AF modes.  The K-1 also focuses more quickly in both AF.S and AF.C mode compared to earlier Pentax models, which we were positively surprised to see.  Quieter focusing with screwdrive lenses (without any sacrifice in terms of speed) is icing on the cake.

While the K-1's autofocus system may not have as many AF points or tracking modes as the latest Canon and Nikon offerings, its performance really is quite good for a camera that's not primarily designed for action use.

In the future, we would welcome changes to live view such that focusing could be possible while the image is magnified.  More focus peaking options would also be beneficial, not to mention the introduction of sensor-level PDAF sensor for basic live view tracking capabilities.  As for the viewfinder AF system, its responsiveness could also be improved for continuous autofocus.


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