Pentax K-3: Performance

November 29, 2013 by Jim Keenan Reads (30,647)
Editor's Rating

Ratings Breakdown (1-10)

    • Image/Video Quality
    • 9
    • Features
    • 8
    • Design / Ease of Use
    • 9
    • Performance
    • 9
    • Expandability
    • 10
    • Total Score:
    • 9.00
    • Rating 1 to 10, top score 10

With Pentax touting the K-3 as featuring “unparalleled technology and specifications” I was anxious to put the ad copy to the test, especially in light of that 8.3 fps motor that just screams “shoot some fast-moving subjects”.

Pentax K-3

Shooting Performance
Before any camera can shoot even one frame per second it first has to be turned on and in this regard the K-3 starts promptly. I was able to power the camera up, acquire focus and get off a first shot in about one second. Ongoing single shots are simply a matter of how rapidly you can reacquire focus and shoot again. AF performance with the K-3 in single still image capture was solid: fairly quick in good light with very little drop-off in acquisition times in dim light. There is an AF assist lamp which seems to have a little more range than that of the K-5II. Overall, AF performance for single image still captures was appropriate given the camera’s price point.

Shifting to continuous high-speed shooting there is mostly good news: first, the camera can really crank out the frames at high-speed, assuming you’re able to keep the shutter speed around 1/600 of a second or faster. As shutter speeds drop into the 1/400th range (and slower) you can hear the camera isn’t quite keeping up the same pace. Another factor is the release priority established for the camera: in the custom menu page 3, items 16 and 17 control release priority for the shutter during the first shot in continuous shooting mode and then all subsequent shots in any individual burst, respectively. With either or both of these settings on focus priority the camera first establishes focus before allowing the shutter to the fire, and the focus process generally slow things down. With the settings on release priority the camera is free to fire away without necessarily establishing focus.

More good news: Pentax has built in a buffer capacity with the K-3 that provides good support for shooters who like to rip a lot of images. Nominally, the K-3 is capable of recording approximately 60 JPEG images or 25 RAW images at continuous high-speed before buffer capacity slows the shooting down. That’s about 7.5 seconds shooting JPEGs and 3 seconds shooting RAW. But just as with focus priority versus release priority impacting the continuous shooting rate, there’s a serpent in the buffer Garden of Eden as well: distortion correction. On page 1 of the record menu there’s a “lens correction” item that, when entered reveals distortion correction, lateral chromatic aberration adjustment, and peripheral illumination correction settings (all part of the shooting settings that can also be accessed on the monitor via the info button). Enabling distortion correction is the guilty party here – shooting continuous high-speed JPEGs buffer capacity is now cut by over half, to about 25-26 images before shooting slows. That’s still a full three seconds, and the camera can also shoot about 25-26 RAW images before slowing; in fact, even shooting RAW and JPEG images the K-3 still made the 26 image figure before slowing. All shooting with the K-3 was done with a Lexar 32GB 600x SDHC memory card.

Write times for distortion-controlled bursts of 25 JPEG images ran about 19 seconds; RAW write times were 25 seconds and the RAW/JPEG 26 image burst took about 35 seconds. During the writing process a card access lamp on the lower right rear of the camera body flashes to let you know the writing status; even with writing still in progress, the K-3 allows you to capture additional images as soon as there is buffer capacity available.

The K-3 offers the ability to bracket up to five images with varying levels of exposure with a single push the shutter button, a handy feature for folks who like to use HDR software to create single composite images out of a bracketed sequence. Somewhat strangely, when I tried bracketing with the K-3 set in manual shooting mode, the camera changed both aperture and shutter speed in each successive shot; generally, a camera bracketing in manual mode retains the same aperture but changes shutter speeds only. Changing the aperture with each shot of necessity will cause slightly different depth of field in each shot you’re later asking your software to merge – probably not the ideal situation. Fortunately for folks who want to let the camera do the work, the K-3 has a fairly competent HDR shooting feature which creates a single image out of a three shot burst – and it’s a good idea to mount the camera on a tripod when using this feature in dim light where it does its best work. Here are a couple shots of modestly dim interiors at Mission San Luis Rey:

Autofocus tracking performance on moving subjects at the continuous high-speed shooting rate was okay, but not spectacular.  With the camera set for AF-C there are expanded area autofocus settings that include some, most, or all of the other focus points besides the user selected point to maintain focus should the subject move off of the selected point. With 16 additional focus points over the K-5II, I expected the K-3 to track fairly well, but tough subjects like hummingbirds proved largely an exercise in futility and even large, fairly slow moving subjects like surfers didn’t seem to produce as many sharp shots as I would have thought. On one occasion, while holding focus in the continuous mode on a stationary hummingbird feeder, I noticed the focus point jumping around to various spots on the feeder, despite the absence of a moving subject. The AF system appeared to be judging that different parts of the feeder which were slightly different distances from the camera constituted a moving subject and was selecting different focus points to compensate.  Overall, I thought that the continuous autofocus performance of the K-3 was comparable to the K-5II – good, and appropriate for the camera’s price point, but my feeling is the additional focus points and the new AF system don’t seem to be a dramatic upgrade from that of the K-5II.

The K-3 built-in flash has a guide number of approximately 42.5 feet at ISO 100 and flash sync speed is 1/180th of a second (both values the same as the K-5II). Many DSLRs offer 1/250th second or faster synch speeds, so the K-3 is giving a little ground here. Flash modes include auto, on, redeye, slow sync, slow sync + redeye, trailing curtain sync, high speed sync and wireless.

Pentax reports battery life for the K-3 as approximately 720 images (560 images with 50% flash usage), a drop of 260 images from that of the K-5II with no flash usage and despite having the same battery.

Lens Performance
The DA 18-135 f3.5/5.6 ED AL (IF) DC WR kit lens, besides being a mouthful to say also shows a bit of barrel distortion at the wide-angle end of the focal range with a milder dose of pincushion distortion at telephoto. Zooming the lens to around 22mm eliminated the barrel distortion but by about 28mm some pincushion distortion was beginning to become apparent, but pincushion is never as pronounced as the barrel distortion. There was slight softness and light falloff  in the corners at 18mm, and the vertical edges of the frame appeared slightly soft as well — the horizontal edges appeared consistent with the rest of the frame. At 135mm the corners appeared a bit soft and the edges slightly soft. Chromatic aberration (purple fringing) was present at both ends of the zoom in this lens, but was relatively benign and primarily noticeable during 300-400x pixel peeping.

Approximately 90 degrees of rotation of the zoom ring is required to go from one extreme focal length to the other, and this action was smooth and consistent. Manual focus required rotation of the focus ring through about 90 degrees of travel and the front element of the lens does not rotate during focus — minimum focus distance is 15.72 inches.

As mentioned earlier the K-3 has a lens correction menu item that includes distortion correction, lateral chromatic aberration adjustment, and peripheral illumination correction settings that, when enabled can help compensate for lens defects.

Video Quality
With the Pentax press release on the K-3 promising “an enhanced video recording experience” and “outstanding HD video performance” I was hoping to see a video capture capability approaching that of the Canon 70D I recently reviewed. No such luck. While Pentax video image quality is good and the K-3 features a redesigned movie interface that makes initiating video capture a smooth process, the Pentax flagship still lacks a continuous autofocus capability. Not even a slow continuous autofocus capability, no capability at all. You can autofocus initially in order to initiate capture, but if your subject moves off the original focus point and in so doing changes its distance from the camera, the camera doesn’t alter focus to compensate for the change. Seriously Pentax, everybody else’s DSLRs have continuous autofocus, why is it you can’t seem to do the same?

I’ll be the first to admit that I do not shoot a lot of video with my personal DSLRs and subscribe to the philosophy that if video capture is your primary objective you should be using a dedicated video cam. Video has been in DSLRs for a while now and all the other guys have continuous autofocus, so the absence of it in yet another Pentax flagship is a major black mark against a camera that otherwise has so much to offer for still image capture.

Outside of the lack of a continuous autofocus capability, video image quality is good and rolling shutter effect is well controlled in all but the most exaggeratedly fast pans. The built in microphone is wind sensitive and picks up other camera noises during recording in the auto setting; audio may also be captured manually or disabled altogether. The camera has an external microphone jack that can facilitate the recording of stereo sound during video capture.

Image Quality
Default image quality out of the K-3 was very good, with colors reproduced with pleasant and accurate saturation and sharpness. Even so, as is my usual practice I did increase the in-camera sharpness level of the “natural” color effect I used to shoot most of the images for this review. “Bright” is the default color effect but the K-3 offers a choice of nine other options including portrait, landscape, vibrant, radiant, muted, bleach bypass, reversal film, monochrome, and cross processing. Here’s a look at bright, natural, monochrome, radiant, muted and cross processing samples.

BRIGHT                                                      NATURAL

MONO                                                  RADIANT

MUTED                                                  CROSS PROC

Lacking a traditional antialiasing filter but featuring a shake reduction-based process to deal with image issues arising from the presence of moire, the 800 pound gorilla in the image quality room becomes how well does the K-3 deal with moire should it appear. Without going into a lengthy and, necessarily, technical dissertation on the how/what/why of moire, for the purposes of this review let’s just very simplistically describe it as instances of false colors and/or patterns that appear in digital images where the subject of the image is composed of a lot of fine, repetitive details. The purpose of an antialiasing filter is to essentially filter out these instances of false color or patterns during the image capturing process; this filtering processes sacrifices a bit of image sharpness in the interest of moire elimination.

The K-3 offers two settings designed to simulate the effect of an antialiasing (AA) filter: type 1 which strikes a compromise between moire reduction and image sharpness, and type 2 which prioritizes moire reduction. First, we’ll look at two sets of images captured using the range of AA simulation available in the K-3: none, type 1 and type 2. These images would not be expected to produce moire and the effect of the various AA simulation effects are slight.

Type 1 AA

Type 2 AA


And another set…

Type 1 AA

Type 2 AA


Next, we’ll look at images of the type extremely likely to produce moire. Bird feathers are often used to illustrate moire as the repetitive details in the feathers lend themselves readily to the production of moire artifacts. Here are three shots of Kiwi taken with the AA simulator off, with type I enabled, and with type 2 enabled, respectively. Personally, I see moire artifacts in all three images, the most prominent logically appearing in the image with AA disabled. The type 1 enabled image provides a bit more moire control and the type 2 even more, without completely eliminating the problem. This AA performance is what I would expect given the performance described each of the simulator types, although having type 2 eliminate the problem would’ve been the preferred end result.

Type 1 AA

Type 2 AA


Given the strong moire-producing nature of bird feathers I’m not overly disappointed that the K-3 AA simulator did not completely eliminate the artifacts in these images, as the subject matter is probably the worst case scenario for the production of moire. I shot a number of other repetitive detail subjects including chain-link and picket fences, textiles and air-conditioning units with wire grills that produced no instances of moire with the AA simulator disabled.

There is always the possibility of post processing to deal with moire that is not removed in-camera to the user’s satisfaction. My Photoshop CS5 does not have a dedicated moire reduction tool, but Lightroom 4 reportedly does. In Photoshop masking and gaussian blur have reportedly been used to post process moire; those techniques can be Googled online. If you’re planning to specialize in bird portraits you might want to pass on the K-3 (or any camera not featuring an AA filter, for that matter), but it handled everything else I managed to throw at it with aplomb.

Finally, ISO performance was a pleasant surprise. With the K-3 sensor picking up so much resolution over its predecessor I was concerned that high ISO noise performance might suffer as a consequence, but the camera turned in a very credible performance. While some slight graininess begins to become visible with pixel peeping at the 400 and 800 ISO settings, a fairly slow and steady progression of increased graininess continues up to and including 6400 ISO. 12800 seems to be the tipping point for this particular sensor as the increase in grain making the jump from 6400 is the most dramatic increase so far. 25600 shows another modest increase while 51200 introduces another significant jump, much akin to the magnitude of change between 6400 and 12800. Keep in mind that all of these images were made with noise reduction disabled in the camera, since I prefer to deal with noise reduction in the post processing phase. Applying in camera noise reduction provided only modest improvement with the 25600 and 51200 images but did a little better with the 6400 and 12800 sensitivities; images with a “NR” suffix include noise reduction.

100 iso200 iso

ISO 100                                                                       ISO 200

400 iso800 iso

ISO 400                                                                       ISO 800

1600 iso3200 iso

ISO 1600                                                                       ISO 3200

6400 iso12800 iso

ISO 6400                                                                       ISO 12800

25600 iso51200 iso

ISO 25600                                                                       ISO 51200

6400 NR12800 NR

ISO 6400 NR                                                                     ISO 12800NR

25600 NR51200 NR

ISO 25600NR                                                                     ISO 51200 NR

Additional Sample Images

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