Pentax K-1 Review

Super Resolution and AA Filter

The Pentax K-1 packs two unique features to further enhance its image quality: Pixel Shift Resolution (PSR) and the AA filter simulator.  Both are facilitated by the camera's Shake Reduction system.

Pixel Shift Resolution concept

PSR is without question the more exciting of the two features.  By moving the sensor around by a single pixel while synthesizing four exposures of the same scene, the K-1 can virtually undo the negative effect of the Bayer pattern.  In PSR mode, details become considerably clearer, edges are better-defined, and colors are more accurate.  What's the catch?  This feature will only provide a visible benefit when photographing perfectly stationary subjects: i.e. landscapes, product photos, or architecture.  Although the K-1 has an in-camera "Motion Correction" option that seeks to suppress artifacts in areas with traces of motion (i.e. trees swaying in the wind or a stray pedestrian), this does not mean that PSR can be used on moving subjects, let alone hand-held.  Attempting to do so will either yield no discernible benefit, or introduce artifacts.  Similarly, the PSR feature is not suitable for portrait photography as it is not reasonable to expect models to stand perfectly still.  Motion Correction will kick in and leave you with a normal resolution photo that will most likely still have some lingering artifacts.

To learn more about the implementation of Pixel Shift Resolution, read our in-depth article on the theory and hands-on tests.

In PSR mode, the K-1 still produces 36-megapixel JPEGs, albeit with much higher detail at the pixel level compared to standard JPEG photos.  RAWs similarly have 36 megapixels, but each RAW file contains the four separate exposures which are automatically merged during development. While PSR RAW files do allow you to squeeze additional dynamic range and detail out of any given photo, the out-of-camera PSR JPEGs are quite good to begin with— and they will save you a great deal of time and space.  PSR RAW files occupy four times the normal space and are typically on the order of 140-200Mb each.  These files can be developed using the in-camera playback mode or using desktop software.  We've found that in sub-optimal shooting conditions when some motion is present, the most effective desktop algorithm for processing these files can be found in Pentax's own Digital Camera Utility software that ships with the K-1.  In addition to having superior interpolation algorithms compared to other software we've tested, the Digital Camera Utility also allows you to apply the Motion Correction feature retroactively, as this feature is strictly based on interpolation. 

If you'd like better control over colors and detail, or if you just want to use your existing presets, Adobe Camera Raw will eventually be able to support the K-1's PSR files, but at the present moment it appears that the software simply processes them as normal RAW's.  Refer to our K-3 II review for information on how to post-process PSR RAW files in Photoshop once proper support is added.

One last thing we'd like to point out is that the K-1 uses an electronic shutter in between PSR captures.  The electronic shutter cannot be activated in other modes, however.

Pixel Shift Tests

That's enough theory for now.  Let's take a look at what happens when we combine the K-1's impressive sensor and resolution with the power of PSR.  Consider this landscape:

Test Scene - shot with the FA* 85mm F1.4 @ F8 and ISO 100

The below crops are taken from full-size JPEGs straight out of camera (i.e. they are unscaled and unaltered).

Looking at the mountaintops near the sky, the PSR version of the photo shows much clearer edges without a prominent glow.  This glow is otherwise introduced through Bayer interpolation, which can't always perfectly guess the missing color data near edges.

We also observe clearer shadow detail:

Looking at a larger crop of the scene, the reds and yellows are more accurate in the PSR version of the image.

Without PSR, the upper part of the cactus is blurred, whereas the PSR version depicts the grooves nearly perfectly.

Finally, PSR makes small details in the distance clearer, leading to a better sense of depth.

If you'd like to take a closer look or experiment more on your own, see the conventional JPEG, pixel shift JPEG, and PSR RAW.

Product photography is perhaps the best application of Pixel Shift Resolution, such subjects can always be perfectly still, and the resulting photos are often viewed at full resolution or heavily magnified.  Consider the photo below:

Product photography test - shot with the FA 43mm Limited F1.9 Limited @ F16 and ISO 100

With PSR on, we observe clearer text and edges, less noise in darker areas, and more accurate colors.  The slider below is a 100% crop of the original:

Again, we provide full-size PSR and non-PSR JPEGs for your evaluation.  The JPEGs have been cropped to mask our backdrop but are otherwise straight out-of-camera.

Ultimately, thanks to PSR the Pentax K-1 makes for an excellent camera for product photography, easily surpassing other 36-megapixel full-frame options currently on the market.

AA Filter Simulator

Moire is generally not an issue thanks to the Pentax K-1's high native sensor resolution.  When shooting textiles, however, it is possible to provoke moire with a fast, sharp lens and the right conditions.

Although the sensor itself has no anti-aliasing (AA) filter in front of it, the Pentax-unique AA Filter Simulator microscopically vibrates the sensor to introduce a slight pixel-level blur to simulate a hardware AA filter.  This feature can be used at any shutter speed and is thus a general-purpose solution.

The test photo in the upper-left corner of the grid below was taken without the AA filter simulator.  In it, we observe some false color and numerous zebra patterns.  With the Type 1 AA filter simulator enabled (the weaker setting), the zebra patterns disappear for the most part, though some false color remains.  Ramping it up to the stronger Type 2 setting effectively eliminates both moire and false color, at the expense of some detail.

Standard Image	AA Filter Simulator Type 1	AA Filter Simulator Type 2
Moire Correction - Weak	Moire Correction - Strong	ACR Moire Brush - 50%

The bottom row of the table below sows that software-based moire removal solutions aren't quite as effective as the AA Filter Simulator.  We tested the K-1's in-camera Moire Correction (accessible in playback mode) as well as the moire brush in Adobe Camera Raw.

Note that these are all 100% crops, so even if you do get some moire in your images, chances are it will not affect prints.  Still, if you're a fashion or wedding photographer, keeping the AA Filter Simulator on is a good idea.  The Type 1 setting offers a balance of detail and moire suppression.

Verdict

Both Pixel Shift Resolution and the AA Filter Simulator work well in practice, though each feature only applies to a limited number of shooting scenarios.  Overall, these features give the K-1 a unique edge over competing cameras.