Pentax K-3 II Review
Image Quality
The Pentax K-3 II delivers impressive still image quality thanks to its filterless 24-megapixel sensor and a host of advanced technologies including an 86k-pixel white balance system, selectable AA filter, and sensor-shift shake reduction. It shares nearly all of its capabilities with the Pentax K-3, and we thus direct you to first take a closer look at the Pentax K-3 image quality analysis before reading on.
New in the K-3 II
Compared to the K-3, the K-3 II has received two enhancements relating to image quality: the pixel shift resolution system and improved shake reduction. Both will be discussed in detail in the following sections.
Pixel Shift Resolution
Pentax's Pixel Shift Resolution is a type of super resolution technology that aims to enhance detail in images by microscopically shifting the sensor to capture additional color data.
In order to get around the limitations of the Bayer sensor pattern, Pentax's pixel shifting implementation captures a total of four consecutive images without closing the shutter. For each image, the sensor is shifted by just one pixel such that at the end of the cycle, each of the 24 million pixels on the sensor has collected full data for all three color channels. If you are interested in learning more, see our technical explanation of how pixel shifting works.
On the K-3 II, pixel shifting can be enabled quickly through the control panel (INFO button) or main menu.
Enabling pixel shifting via the control panel
This pixel shifting process feels much like an in-camera HDR image capture, except that the mirror stays up for the duration of the exposure. With pixel shift resolution enabled, exposures will take at least four times the selected shutter speed. When very fast shutter speeds are selected, the whole process lasts about a second. Once the camera has finished the exposure, it processes the picture data for a few more seconds, and then saves the image. The video below illustrates the whole process, shot in live view using the IR remote:
Even with fast shutter speeds, there is a slight delay in between captures. This makes pixel shifting unsuitable for hand-holding.
Following the capture, in JPEG mode, the camera will process the sensor data for a few seconds and save a JPEG file with the resulting enhancements. When shooting in RAW, on the other hand, there is no additional in-camera processing The output RAW file will contain four embedded images that will need to be combined/interpolated by your image processing software. While pixel shifted JPEGs are typically no larger than traditional files, RAWs are on the order of 110 to 130Mb each (4 times bigger than normal). If your post-processing software does not support pixel shifted RAW files, the processed version will look just like an ordinary photo without pixel shifting.
Unless otherwise noted, all pixel shifting examples on this page are based on out-of-camera JPEGs.
Post-processing pixel shifted files is a topic of its own and will thus be discussed on the following page.
When To Use It
Super resolution technology is ideal for shooting any static subject as long as the camera is firmly secured (i.e. on a tripod) and perfectly motionless. Suitable applications include product photography, reproductions, real estate, and more. You can also enable pixel sifting for landscapes when winds are calm and there are no moving objects.
We recommend using a remote and/or the self-timer whenever you enable pixel shifting, as vibrations can potentially ruin the image.
Let's start with a quick illustration of the amount of detail pixel shifting can bring out in ordinary photos. Consider this ornament that we photographed with the DA 18-135mm zoom lens set to 40mm, F9.5.
Pixel shifting test scene
Use the slider below to compare the results at 100% with and without pixel shifting:
With pixel shifting on, the originally-soft image looks better than what you might otherwise get from a top-shelf lens.
Download the cropped full-size original with pixel shifting / without pixel shifting for an even closer look.
When Not to Use It
In the majority of everyday shooting situations, pixel shifting should not be used.
Hand-held
Unless you can become as motionless as a tripod, combining pixel shifting with hand-holding will result in an improperly-merged image that may look worse than a conventional image.
Zipper artifacts due to misaligned portions of the image
Selecting a fast shutter speed doesn't help as the camera pauses briefly in between exposures. Even if it didn't, all but the slightest of motion is enough to spill light onto the wrong neighboring pixels, thus causing errors during processing. Just a few microns of movement on the sensor can ruin everything.
While JPEG files shot of moving subjects shot with pixel shifting are generally not going to be recoverable, RAW files can in fact be developed as conventional images using one of the four embedded photos, if needed.
Moving Objects
Pixel shifting offers no benefit for moving subjects. Interpolation of the four greatly misaligned images will result in ghosts similar to what you might get when shooting with a slow shutter speed.
A slow-moving ship shot with pixel shifting enabled - click to enlarge
Birds - 100% crop
Wind / unstable setup
Even if your camera is on a tripod, windy conditions or a setup that isn't perfectly stable may result in "fuzzy" details at the pixel level. In these cases, it is advisable to inspect the image and make sure that none of the artifacts are visible in your final print.
Slight instability - 2x enlargement of 100% crop
Real-World Examples
We had the most success when applying pixel shifting to product photography. Consider the image below:
Train sample 1 - original JPEG | RAW
At the pixel level, this image contains a remarkable amount of detail. Specifically, edges are perfectly sharp and fine details right next to each other are clearly distinguishable. Moreover, colors in the pixel-shifted image are more accurate. This can be verified by processing the RAW files linked above (115Mb). The images were taken with the D FA 100mm F2.8 macro.
Sample 1 - 100% crop
We provide two additional full-size samples below should you wish to experiment.
Sample 2 - original 
Sample 3 - original We also found pixel shifting to be quite effective for macro applications. Use the slider below to compare a 100% crop of a conventional JPEG to a crop of a pixel-shifted JPEG straight out of camera:
Again, we observe more accurate colors and clearer details. See also the original conventional and pixel-shifted JPEGs.
Landscape Photography
While indoor photography allows the most control over your rig, pixel shifting is also appropriate for landscape/architecture photography as long as everything in the frame is stationary.
Landscape test scene
As in our previous examples, pixel shifting greatly improved the pixel-level detail in this scene. Below is a 100% crop with pixel shifting enabled. Even with a consumer-grade lens (again, the DA 18-135mm), the pixel-level detail is razor-sharp:
100% crop of the test scene - click for entire image
Let us consider a wider field of view:
Second test scene
Upon examining the entirety of the the scene (conventional, pixel-shifted), we observe that the camera was in fact not perfectly steady on our 15-lb tripod. It was a somewhat breezy day, and for this photo, the tripod was out in the open. Despite this, the pixel-shifted version still appears sharper out-of-camera; while pixel-level zipper artifacts occur here and there, they are difficult to spot if the image is scaled. Use the slider below to compare 100% crops of the two versions of the image:
Out of curiosity, we then applied an unsharp mask to the original JPG to see how it would compare to the pixel-shifted version:
Here, the difference between the two is not as easy to discern, though pixel shifting still ends up on top. We can conclude that pixel shifting will not always have a clear benefit for landscape use when there is wind, as even microscopic vibrations can cancel out the increase in clarity you would otherwise expect.
Reproductions / Enlargements
The pixel shifting feature is well-suited for reprophotography.
Original image
In this case, the camera (with a D FA 100mm macro lens at 1:1 magnification) out-resolved the detail in a 50 dollar bill. See the full-size crop below:
Pixel shifting delivers clearer edges and can lead to better master files for reproductions or enlargements of photos, artwork, documents, etc.
Color Accuracy and Noise at High ISOs
Images captured with pixel shifting enabled contain less noise and richer colors compared to conventional images. Click on any thumbnail below for a larger view, then use your arrow keys or mouse scroll wheel to compare it with the next. These images have been scaled to be web-friendly, but not cropped.
ISO | Standard | Pixel Shifted |
| 100 |  |  |
| 200 |  |  |
| 400 |  |  |
| 800 |  |  |
| 1600 |  |  |
| 3200 |  |  |
| 6400 |  |  |
| 12800 |  |  |
| 25600 |  |  |
| 51200 |  |  |
Since pixel shifting requires a perfectly steady rig for optimal results, it is somewhat moot to shoot at anything other than base ISO. Still, these tests show that the technology works and that even at higher ISOs, colors appear more vivid.
The Bottom Line
When used correctly, the K-3 II's pixel shifting feature can greatly increase the pixel-level resolution of images. Currently, the applications of this technology are mostly limited to technical (rather than artistic) types of photography. Still, it has proven to be quite robust for a first-generation system, and it can already greatly benefit product and architectural photographers. Pixel shifting offers the greatest practical benefit for large prints or crops/enlargements.
With an unstable setup, pixel shifting can backfire when used in JPEG mode. For critical photos we therefore recommend shooting in RAW+, so that the RAW file can be used to obtain a standard exposure when the out-of-camera JPEG shows an excessive amount of artifacts.
In its current state, pixel shifting should never be used hand-held and is thus something we wouldn't consider to be a mainstream feature.
Shake Reduction
Per its specifications, the K-3 II's new Shake Reduction system can compensate for up to 4.5 stops of camera shake. This represents a one-stop increase compared to the K-3, which was rated for 3.5 stops of stabilization.
In practice, the minimum feasible shutter speed will depend on the focal length of your lens and the stability of your hands.
It was difficult to perform a controlled comparative test of the new SR system. After using a variety of lenses on both the K-3 II and K-3, we were unable to find a scenario in which the shutter speed selected on the K-3 II resulted in blurry images on the K-3. We can thus only speculate that the SR improvements placed in the K-3 II have been developed in anticipation of the upcoming full frame DSLR.
With wide-angle and normal lenses, slow shutter speeds such as 1/8s, 1/6s, and 1/4s proved to be no trouble for the K-3 II's shake reduction.
Test scene - FA 31mm, 1/4s, F2.8 - click to full size JPEG developed from RAW
See below for a full-size crop from this scene:
For low-light photography we always recommend shooting in RAW for the added control over color and detail that it offers.
Verdict
Like the K-3, the K-3 II continues to be cutting-edge when it comes to APS-C image quality. Thanks to the pixel shifting feature, the K-3 II offers an even larger suite of advanced options for technically-inclined users to play with. However, in everyday shooting scenarios (those that preclude the use of pixel shifting), the two cameras deliver the same performance. We will thus generally continue recommending the K-3 just as much as the K-3 II to users who don't frequently shoot products or architecture in controlled environments.
When used correctly, pixel shifting can increase color accuracy and the level of detail in images. This can be especially beneficial for product photography. Pixel-shifted RAW files deliver more control over details, as we will investigate on the following page.
