Exploring the K-3 II's "Pixel Shift Resolution" mode

by Mike Tomkins | Posted: 05/28/2015

With the Pentax K-3 II, Ricoh debuts a brand-new feature that will be of great interest to anyone hoping to maximize per-pixel sharpness. Dubbed Pixel Shift Resolution, this function captures multiple images and combines them to create a single shot with higher resolution, much like the High Resolution mode of the Olympus E-M5 II, which was announced just a couple of months earlier. (You can compare the Pentax K-3 II vs. Olympus E-M5 II here, if you like.)

There are some important differences in the way the two technologies work, but both share the same key limitation: They only work with static subjects, and with the camera mounted on a tripod. If you're able to live with that fact, though, they promise even greater resolution than can be derived from a single shot, thanks to the Bayer filter that overlies the image sensor on almost every color-capable camera. And if that's not enough for you, they can also reduce the incidence of moiré and false color, not to mention improving noise levels and grain size.

Similarities, but with a key difference in technologies

Both cameras create their high-resolution images by capturing multiple shots in sequence, and adjusting the sensor position just fractionally between shots using the sensor-shift stabilization mechanism so that the light at any given location falls on different sensor pixels. Where typically a camera using a Bayer-filtered sensor must interpolate (or in essence, guess) the values for two out of the three red, green and blue channels for every pixel, this technique allows full color information to be recorded directly at every pixel.

So what separates Ricoh's approach in the Pentax K-3 II from that selected by Olympus in the OM-D E-M5 II? Olympus is moving the sensor in steps that are smaller than its pixel size, and then capturing a total of eight frames to create a single output image. Ricoh, by contrast, is using full pixel-sized steps and combining half as many frames per image, with a total of four images captured per output frame.

Pentax K-3 II's Pixel Shift Resolution System captures four images with slightly different sensor positions, and combines them into a single shot with full color information at every pixel location.

Olympus' approach to the problem gives it more data to work with, and allows resolution to be improved well beyond what the sensor resolution would suggest -- final output resolution is 40 megapixels in JPEG mode or 64 megapixels in raw -- but it also presents a much more complex problem for the camera, and requires finer sensor positioning. With less data to juggle for every pixel, Ricoh's approach is much more easily solved, and yet it still triples the amount of information for each pixel compared to a single-shot capture shot with the same sensor.

And as an added advantage, it does so without significantly increasing file sizes, at least so long as you're shooting in JPEG mode. In raw capture, though, the Pentax K-3 II's Pixel Shift Resolution images have about 3.7 to 3.8 times the file size of a standard raw file. You can expect some very, very large file sizes if you intend to shoot in raw format using Pixel Shift Resolution, on the order of 121-122MB even at base sensitivity, and likely even larger as your ISO sensitivity setting climbs. That's equally true of Olympus' rival, though, with file sizes of around 100MB for its High Resolution-mode raw files, about five times the size of its standard raws.

Also, it's worth noting here that since its sensor has around 50% more pixels than that in the E-M5 II there's less need for Ricoh's DSLR to increase resolution as does its mirrorless rival in the first place. Olympus has a resolution deficit to make up compared to its APS-C sensor-based rivals; the Pentax K-3 II doesn't.

But how do these techniques compare in the real world? Which camera gives the most potential for detail-gathering in a sub-frame sensor, and how do these clever tricks compare to simply shooting with a camera using a larger, higher-res sensor in the first place? That's the first thing we wanted to know when we got our hands on the Pentax K-3 II, and so we queued up some comparisons just as soon as we got the camera into the lab for testing.

To start off with, we decided to compare the Pixel Shift Resolution mode against a standard shot from the K-3 II, just to see how much difference the multi-shot technique was capable of making over a single-shot capture.

Standard and Pixel Shift Resolution modes compared

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 For two images shot moments apart using the same camera and sensitivity, the difference here is very impressive. Pixel Shift Resolution brings out the fine thread patterns in the fabric swatches that are almost completely lost in the standard single-shot image.

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Again, there's a significant difference here. Where the single-shot image blurs together the finest markings of the proportional scale, they're clear and distinct in the Pixel Shift Resolution image.

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 And once more, there's an eye-opening difference here in the pepper grinder. The peppercorns show much more fine detail that really makes them pop, giving them a more three-dimensional look.

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 If anything, the difference is even more noticeable in these fabric crops. Where the single-shot image loses almost all thread detail in the fabric, it's faithfully rendered thanks to Pixel Shift Resolution.

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Taking a look at the Samuel Smith label, Pixel Shift Resolution gives a much better rendering of the smallest fonts. Look in particular at the badges over the hop flowers, which are difficult to read in the standard image, but quite clear with Pixel Shift Resolution enabled.

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Here, the greater detail extracted by Pixel Shift Resolution is particularly noticeable in the fiddler's beard, and the stripes in his pants that are almost completely lost in the single-shot version of the same image.

Single-frame shot from the Pentax K-3 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 You'll want to fetch your duster if you're shooting in Pixel Shift Resolution mode. Not only did it do a much better job than the single-shot image with the extremely fine detail in the mosaic pattern, it also picked up the fact that our still life target needs a quick dusting again! Sure, a few specks of dust are visible in the standard shot as well, but not nearly as many as in the Pixel Shift Resolution version.

Ricoh's Pixel Shift Resolution versus Olympus' High Resolution

No question, then, that Pixel Shift Resolution can significantly increase per-pixel sharpness over a standard shot, at least so long as your subject isn't moving and you're using a suitably sharp lens. How does it perform compared to Olympus' equivalent function, though?

Here, resampling is needed to make a valid comparison, as the Olympus E-M5 II creates a higher-resolution JPEG than does the Pentax K-3 II when their respective high-res multi-shot modes are enabled. For fairness, we've tried both upsampling the K-3 II's shots to match the frame height of those from the E-M5 II, and downsampling those of the Olympus to match the Pentax.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) Right off the bat, we'll say that we're comparing both cameras specifically in terms of detail here. Obviously their color rendering is quite different, but that's for comparison elsewhere in our review. Both the K-3 II and E-M5 II turn in a pretty impressive performance. Despite the difference in output resolution for the two cameras, we think this one's too close to call -- from this particular crop, at least!

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) Again mighty close, but we're going to call this one in favor of the Olympus, albeit only because the Pentax K-3 II's image looks just a little oversharpened. Both cameras are batting well above their weight here, and have managed to gather every last speck of detail from the proportional scale.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) Here, the Pentax K-3 II looks to have a noticeable edge over the Olympus E-M5 II. The peppercorns in the grinder are a good bit sharper and more detailed-looking in the K-3 II's shot, although a touch of sharpening on the E-M5 II image would likely bring the two closer to parity.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) In the yellow and orange fabric swatches, we're back to the situation we started in. The difference between these two cameras in terms of fine detail gathering in their high-res modes is so subtle that it's almost impossible to make a call for either.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) Here, the E-M5 II's shot looks just slightly crisper overall, yet in the tiny badges over the hop flowers, the K-3 II looks to show more detail at first glance. To our eye, that's an artifact of the Pentax's slightly stronger default sharpening, but it's a very close thing.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) Moving to the Fiddler's Elbow label, this time it's the Pentax that looks to have a slight advantage over its rival, with just a touch more fine detail visible in the bear and pants leg. Again, though, this is pixel-peeping to a degree that's not likely to make a noticeable difference in the real world.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Olympus frame height) High Resolution-mode shot from the Olympus E-M5 II at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 High Resolution-mode shot from the Olympus E-M5 II at ISO 100 (downsampled to match Pentax frame height) Finally, in the mosaic label the Pentax K-3 II looks to have a very slight edge once more, but that's in part down to more aggressive sharpening. Really, there is very, very little indeed to separate these two cameras in terms of detail gathering, once their respective multi-shot, high-res modes are enabled.

Pixel Shift Resolution versus the Nikon D810

But what of a really high-res, full-frame camera? We'd dearly have loved to make a comparison to the highest-resolution model of the bunch here, the Canon EOS 5DS R (Pentax K-3 II vs. Canon EOS 5DS R), but that wouldn't have been fair given that as of when this report was published, we'd not yet gotten our hands on a final production-level camera, only a beta model. That being the case, we instead opted for the next best thing: the Nikon D810 (Pentax K-3 II vs. Nikon D810).

With a sensor resolution of 36.3 megapixels for the D810 versus the 24.35-megapixel sensor in the K-3 II, not to mention a much larger sensor area for the Nikon, this should be very interesting indeed. Can Pentax's clever Pixel Shift Resolution technique level the playing field? Let's see!

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) Things are looking good for the Pentax K-3 II straight away. In terms of detail in these fabric crops, its Pixel Shift Resolution mode looks to have managed to catch up to the D810 despite a near-50% deficit in pixel count. And for an added bonus, while the D810 shows a pronounced moiré pattern in the troublesome red swatch, there's no such issue in the K-3 II's shot. (That's no knock on the D810, incidentally. We've seen similar moiré in still life shots from a number of other high-res cameras.)

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) Again, a rather similar performance from these two very different cameras. Of course, it's worth bearing in mind that the Nikon D810 can manage this performance in a single shot -- and so, handheld with moving subjects. For the Pentax K-3 II's Pixel Shift Resolution mode, you'll only get the benefit of this kind of resolution when shooting completely static scenes from a tripod.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) Here, the Pentax K-3 II looks to have a little bit of an edge over the D810, just as it did with the E-M5 II. (Could this be the ultimate camera for photographing peppercorns? Perhaps!) ;) Joking aside, we see a little more detail in the K-3 II's shot, although a touch of unsharp mask would bring the D810's image to life.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) In the yellow and orange fabric crops, we have another interesting result. The Pentax K-3 II looks to best the Nikon D810 just slightly, better rendering the fabric patterns in both swatches. It's not a night-and-day difference, but it's certainly enough to be noticeable.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) And again, the K-3 II's Pixel Shift Resolution functon looks to match or even just slightly better the detail possible in a single Nikon D810 image. As in the first crop above, the Nikon D810 again faces troublesome moiré from the halftone pattern in the label, which the Pentax manages to avoid.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) And once more, it's near-impossible to call one of these cameras' result noticeably better than the other in terms of their detail-gathering capability. This is one seriously impressive demonstration of just what Pixel Shift Resolution can do for you with the right subject!

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match Nikon frame height) Shot from the Nikon D810 at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Nikon D810 at ISO 100 (downsampled to match Pentax frame height) Finally, we come to the mosaic label, and here there's no clear winner once more. Overall, the performance between these two cameras is very, very similar so long as you're shooting a static subject and using the Pentax's Pixel Shift Resolution mode. That doesn't hold true as soon as you're shooting moving subjects, of course, but this could be big news for Pentaxians who do a lot of still life work!

Pixel Shift Resolution versus the Pentax 645Z

The comparison against the Nikon D810 is mighty impressive for the Pentax K-3 II's Pixel Shift Resolution mode, but what of the most detail-hungry camera in Ricoh's own lineup?

The mighty Pentax 645Z medium-format DSLR (Pentax K-3 II vs. Pentax 645Z) sets a very high bar indeed, and we're really not expecting the K-3 II to come that close, but we couldn't resist making the comparison nonetheless. A 24.35-megapixel, US$1,100 camera head-to-head against a 51.4-megapixel, US$8,500 camera? Heck, why not? :)

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) No surprise here: Even against the might of Pixel Shift Resolution, the Pentax K-3 II can't match its mighty sibling. The 645Z extracts more detail from our fabric swatches, although perhaps not by quite the margin we were expecting. If you're not going to use the full resolution of the 645Z, though, it seems that downsampling to K-3 II resolution isn't going to result in noticeably better detail than that which Pixel Shift Resolution can already manage.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) Again, the Pentax K-3 II does better against the 645Z than you could fairly expect, but it can't quite match the outright resolution of its professional sibling. (And it doesn't matter whether you upsample the K-3 II or downsample the 645Z: Either way, the enthusiast DSLR shows more haloes from sharpening than will the pro camera.)

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) It's pretty clear, once again, that the medium-format camera is extracting more detail from the scene than can its APS-C sensor-shod sibling.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) It's in the yellow and orange fabric swatches that the Pentax K-3 II's Pixel Shift Resolution function comes closest to matching its high-end sibling's single-shot performance. It's really quite an impressive result for this much more compact enthusiast DSLR, holding onto just a touch more detail in the yellow swatch, and giving just a little back in the orange leaf swatch.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) Looking at the Samuel Smith label, the Pentax 645Z extracts more detail, but it's accompanied by a moiré pattern in the flat green area at the top of the label, as the higher-res camera is confused by the halftone pattern. With that exception, though, this is another clear victory for the medium-format camera, once again with the Pixel Shift Resolution-enhanced K-3 II still turning in a very respectable effort.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) It's pretty clear from this comparison in particular that the 645Z still has a significant lead. The K-3 II does extract a lot of detail out of the Fiddler's Elbow label, but Ricoh's professional offering manages to find still more. Once again, though, if you're not using the full resolution of the 645Z and would need to downsample to K-3 II resolution, there's nothing to be gained over having shot with the much more affordable model in the first place, at least in terms of detail gathering.

Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 (upsampled to match 645Z frame height) Shot from the Pentax 645Z at ISO 100 Pixel Shift Resolution shot from the Pentax K-3 II at ISO 100 Shot from the Pentax 645Z at ISO 100 (downsampled to match K-3 II frame height) And finally, we come to the mosaic label. Once again, another strong effort from the Pentax K-3 II, but it simply can't manage to erase a 50% resolution deficit, Pixel Shift Resolution or no. It's pretty clear that if you're a Pentaxian looking for the absolute maximum image detail, the 645Z is still the camera for you. It's more than a little impressive just how well the plucky K-3 II managed in this comparison, though. Consumer and enthusiast photographers shooting on the K-mount now have an option available to them -- for still life subjects, at least -- that offers absolutely first-class detail gathering. And there's more to it than that, as we'll see in a moment!

Pixel Shift Resolution promises lower noise, too!

Another advantage of this multi-shot technique, as we said at the outset, is that it can significantly reduce noise levels. For our final comparison, we offer a side-by-side look at how noise levels and detail differ between single-shot and Pixel Shift Resolution modes across the Pentax K-3 II's ISO sensitivity range!