Pentax K-r Image Quality

Saturation & Hue Accuracy
Good color and hue accuracy overall, with mild to moderate oversaturation and shifts in some colors.

Saturation. The Pentax K-r's default image tone setting of "Bright" pushes some colors such as blues, greens, reds and purple, but not by as much as previous Pentax entry-level models. The K-r's 12.2% oversaturation is fairly typical, and much lower than the K-x's 21.4%. Overall, images were still bright and punchy, but color wasn't "over the top" as they were for the K-x. You can of course always select a different image tone preset (see below) and/or adjust settings such as saturation and contrast to suit your own tastes. Most consumer digital cameras produce color that's more highly saturated (more intense) than found in the original subjects. This is simply because most people like their color a bit brighter than life.

Skin tones. Caucasian skin tones from the Pentax K-r were a touch cool using auto white balance, while manual white balance produced a slightly warmer, "healthier" appearance. Lighter skin tones looked about right, but darker ones had a slightly yellow/orange cast. Where oversaturation is most problematic is on Caucasian skin tones, as it's very easy for these "memory colors" to be seen as too bright, too pink, too yellow, etc.

Hue. As with most cameras, the Pentax K-r showed a few color shifts relative to the correct mathematical translation of colors in its subjects, but had good accuracy overall when using default settings. Most noticeable was a shift in orange toward yellow, with some shifts in greens, cyans and reds as well. (The cyan to blue shift is very common among the digital cameras we test; we think it's a deliberate choice by camera engineers to produce better-looking sky colors.) Average "delta-C" color error when corrected for saturation was 5.03, which is pretty good, and much better than the K-x's 7.14 score (lower scores are better). Hue is "what color" the color is.

Custom Image
The Pentax K-r offers nine preset "Custom Image" options. You can adjust Saturation, Hue, High/Low Key, Contrast, Sharpness, Filter Effects and Toning parameters to your liking. (Some adjustments are not available depending on the Custom Image type.)

Mouse over the links above to see the effect of the presets on our Still Life target. Click on a link to load the full resolution image.

Saturation Adjustment
The Pentax K-r lets you adjust the image Saturation and Contrast in nine steps each (Hue, High/Low Key and Sharpness are also adjustable in nine steps.) As can be seen below, the saturation adjustment worked well, providing a reasonably fine-grained adjustment over a useful range of control. The saturation adjustment also has almost no impact on contrast. That's how a saturation control should work, but we've often found interactions between saturation adjustments and image contrast (and vice versa) on the cameras we test.

The series of shots above shows results with several different saturation adjustment settings, showing the minimum step size around the default, as well as both extremes. See the Thumbnails index page for more (look for the files named KROUTBSATx.JPG). Click on any thumbnail above to see the full-sized image.

Exposure and White Balance

Indoors, incandescent lighting
Warm results with Auto, cool with Incandescent, though good color with Manual white balance setting. No exposure compensation required.

Indoors, under normal incandescent lighting, color balance was quite warm with the default Auto white balance setting, with a fairly strong orange cast. Like other more recent Pentax SLRs, the K-r features an "Automatic White Balance in Tungsten" setting in a Custom menu. Options are "Subtle" and "Strong" correction, with the default being Subtle. The Strong setting performed better than Subtle resulting in a reduced orange cast, but it produced a slightly magenta tint. Results with the Incandescent setting were a bit too cool, with a bluish cast. The Manual setting was the most neutral and accurate. Note that there is also a Color Temperature Enhancement (CTE) white balance mode, which strongly intensified the orange/yellow cast in our indoor test shot. The Pentax K-r required no exposure compensation for our indoor scene, which is very good. (The average among cameras we've tested is +0.3 EV.) Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source, but a very common one in typical home settings here in the U.S.

Outdoors, daylight
Bright, slightly cool colors with high default contrast. About average exposure accuracy in our "Sunlit" Portrait shot, but our Far-field House shot was overexposed.

Outdoors in bright sunlight, the Pentax K-r struggled a bit with high default contrast. Exposure accuracy was about average for our "Sunlit" Portrait, requiring +0.7 EV compensation for an exposure with good brightness in the face, but that resulted in quite a few clipped highlights in the mannequin's shirt and flowers. Shadow detail was pretty good, however. Skin tones were just a touch cool using Auto white balance, while Manual white balance was warmer but produced stronger yellow/orange tints. The Far-field House shot was overexposed using the default exposure (no exposure compensation), as quite a few highlights were clipped in the white trim, though again shadow detail was pretty good. Color was also a touch cool. See below to see how the Pentax K-r's Contrast, D-Range and HDR settings help in tough situations like these.

See full set of test images with explanations
See thumbnails of all test and gallery images

Resolution
High resolution, 1,600 ~ 1,700 lines of strong detail.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,700 lines per picture height in the horizontal direction, and about 1,600 in the vertical direction. Extinction didn't occur until around 2,400 to 2,600 lines. Adobe Camera RAW processed RAW files showed a bit more resolution, perhaps 100 lines more in the horizontal direction, though results were crisper and remnants of the pattern extended well past 2,600 lines. There were also quite a few moire interference patterns near or above the resolution limit in both the camera JPEG and ACR converted RAW file, indicating a slightly weak anti-alias (AA) filter. Use these numbers to compare with other cameras of similar resolution, or use them to see just what higher resolution can mean in terms of potential detail.

See full set of test images with explanations
See thumbnails of all test and gallery images

Sharpness & Detail
Very sharp, detailed images overall, though moderate edge-enhancement on high-contrast subjects. Moderately low noise suppression visible at base ISO.

Sharpness. The Pentax K-r produced very sharp images with good detail at default settings, though default sharpening and contrast was a bit high. Some edge enhancement artifacts were visible on high-contrast subjects such as the halos seen around some of the branches in the crop above left, but overall results are likely still quite pleasing to the target market (and of course you can always turn down sharpening and/or contrast if you like). Edge enhancement creates the illusion of sharpness by enhancing color and tonal differences right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows some minor detail loss due to noise suppression at base ISO, as individual strands of hair in darker and lower contrast areas began to merge. Still, good results here, especially for an entry-level DSLR. Noise-suppression systems in digital cameras tend to flatten-out detail in areas of subtle contrast. The effects can often be seen in shots of human hair, where the individual strands are lost and an almost "watercolor" look appears.

Color Moire. We noticed color moire interference patterns in our mannequin's green jacket at ISOs up to 400 (see crops at right, and mouse over the links to compare ISOs), and in other test shots such as our Still Life series (check out the "Pure  Brewed" text on the beer bottle label), indicating a somewhat weak anti-alias (AA) filter. We also saw this with the K-x and some other cameras, so it's not that unusual. The Pentax K-r's default (chroma) noise reduction eliminated most of the color moire at ISO 800 (and above) in the jacket, though you can still make out a very faint monochrome pattern. Color moire is still quite visible in the Still Life at ISO 800 however, so enabling NR at low ISOs may not help depending on the subject. We detected it in some of our gallery shots too, as they were taken with the sharp Pentax 17-70mm F4 AL lens, so it is something to be aware of in real-world shots as well, especially when using a sharp lens.

RAW vs In-Camera JPEGs
As noted above, the Pentax K-r does a pretty good job at capturing lots of detail, but more detail can be obtained from carefully processing RAW files while simultaneously reducing sharpening artifacts. Take a look below, to see what we mean:

In the table above, mousing over a link at the bottom will load the corresponding crop in the area above, and clicking the link will load the full resolution image. Examples are shot at ISO 100, and include in-camera Premium JPEG as well as the matching RAW file processed through Adobe Camera Raw (ACR) version 6.4, then sharpened in Photoshop. For the Pentax K-r's RAW files, we found best results with strong but tight 300% unsharp masking with a 0.3 pixel radius.

As is frequently the case, the demosaicing and sharpening in Adobe Camera Raw and Photoshop delivered finer detail than the camera JPEGs. Looking very closely at the images, ACR extracted noticeably more detail that wasn't present in the JPEGs, but rendered colors and contrast differently than the default camera settings. There's also a bit more noise visible though it's pretty fine-grained. You can always adjust most processing parameters to your liking after shooting, though, which is one of the advantages of shooting RAW and processing the images yourself.

ISO & Noise Performance
Low noise at normal sensitivity settings, with very good detail vs noise up to ISO 800. 

The Pentax K-r produced images with low noise at its lower sensitivity settings, and even at ISO 400, noise was quite low with little detail lost to the noise reduction. (The K-r's default high ISO noise reduction doesn't kick in until ISO 800.) Shadows showed just a touch of chroma (color) noise at ISO 400. At ISO 800, noise "grain" was more visible and there was some minor blurring due to the added noise reduction, though chroma noise was less evident than at ISO 400 in the shadows. ISO 1,600 showed more noticeable blurring from stronger noise reduction, but detail was still pretty good. ISO 3,200 wasn't bad either, though there was another noticeable drop in fine detail, and chroma noise blotches were more visible in shadow areas and in the hair. ISO 6,400 suffered from darker noise pixels and other artifacts as the camera attempted to maintain the appearance of detail, while chroma noise started to become an issue in the shadows. Things got pretty ugly at ISO 12,800 and especially 25,600, with much stronger blurring along with obvious purple and green chroma blotches. Still, a good performance here for an entry-level APS-C model, though some newer models with higher resolution do just as well or better. See the Print Quality section below for recommended maximum print sizes at each ISO.

A note about focus for this shot: We shoot this image at f/4, using one of three very sharp reference lenses (70mm Sigma f/2.8 macro for most cameras, 60mm f/2.8 Nikkor macro for Nikon bodies without a drive motor, and Olympus Zuiko 50mm f/2.0 for Four Thirds and Micro Four Thirds bodies). To insure that the hair detail we use for making critical judgements about camera noise processing and detail rendering is in sharp focus at the relatively wide aperture we're shooting at, the focus target at the center of the scene is on a movable stand. This lets us compensate for front- or back-focus by different camera bodies, even those that lack micro-focus adjustments. This does mean, though, that the focus target itself may appear soft or slightly out of focus for bodies that front- or back-focused with the reference lens. If you click to view the full-size image for one of these shots and notice that the focus target is fuzzy, you don't need to email and tell us about it; we already know it. :-) The focus target position will simply have been adjusted to insure that the rest of the scene is focused properly.

Extremes: Sunlit, dynamic range and low light tests
High resolution with strong overall detail, but slightly high contrast with hot highlights. Good low-light performance, capable of capturing bright images in near darkness, though autofocus and metering struggled at lower light levels.

Sunlight
The Pentax K-r produced slightly high contrast with some washed-out highlights and deep shadows under the harsh lighting of the test above. (The camera's default Image Tone setting is "Bright", which uses +1 out of a range of -4 to +4 for Contrast.) Shadow detail was pretty good, though, despite some minor image noise. Our "Sunlit" Portrait target required +0.7 EV exposure compensation for a reasonably bright face, which is average for this shot. Some may prefer the +1.0 EV exposure for its brighter face, but we thought too many highlights were blown, and skin tones were washed out in some places.

Because digital cameras are more like slide film than negative film (in that they tend to have a more limited tonal range), we test them in the harshest situations to see how they handle scenes with bright highlights and dark shadows, as well as what kind of sensitivity they have in low light. The shot above is designed to mimic the very harsh, contrasty effect of direct noonday sunlight, a very tough challenge for most digital cameras. (You can read details of this test here. In actual shooting conditions, be sure to use fill flash in situations like the one shown here; it's better to shoot in open shade whenever possible.)

Contrast Adjustment
Just as with its saturation adjustment, the Pentax K-r's contrast adjustment offers a fairly wide range of settings (-4 to +4), and the contrast steps are actually a little finer than those for saturation, which is even more to our liking.

At its lowest contrast setting, the K-r did a really excellent job of bringing nice detail out of the shadows as well as preserving a bit more highlight detail in the model's shirt and flowers, but skin tones in the "Outdoor" Portrait were a bit too flat for our tastes, and colors in general in the Far-field House shot were noticeably less saturated.

The series of shots above shows results with several different contrast adjustment settings, showing the minimum step size around zero, as well as both extremes. The Pentax K-r actually defaults contrast to +1. The camera's contrast adjustment had quite an effect on color saturation, reducing it along with contrast. Contrast and saturation are actually fairly closely coupled, so this is unfortunately not unusual. While you can see the extremes, it's hard to really evaluate contrast on small thumbnails like these, click on any thumbnail to go to the full-size image.

Face Detection
The Pentax K-r has a Face-Detection AF option in Live View mode.

Face Detection AF in Live View mode adjusts exposure as well as focus when it detects a face, according to the Pentax K-r user manual. As you can see above however, the image with Face Detection AF enabled (center) was actually dimmer than without (left) despite detecting a face (according to EXIF) because it selected a slightly faster shutter speed (1/50s vs 1/40s). Perhaps it was limited by the exposure mode we used (Aperture Priority). Auto Picture mode selected Portrait scene mode which employed a wider aperture (f/3.2), faster shutter speed (1/250s), and slightly reduced contrast and sharpening, but results were still a bit dimmer than our standard shot (left) using regular Aperture Priority at f/8.

D-Range Settings
The Pentax K-r's D-Range feature offers three Shadow Correction levels (Low, Medium, and High) as well as one Highlight Correction setting (On/Off). As the name implies, Shadow Correction works to raise shadow levels while attempting to keep highlights and midtones as they are, and likewise, Highlight Correction attempts to reduce highlights without darkening shadows and midtones. Both can be used simultaneously. See the images below to see their effect on our high contrast "Sunlit" Portrait test shot.

Mouse over the links to see how the various settings for D-Range affect our "Outdoor" Portrait shot. Click on a link to get to the full-res image. (The effect can be a little subtle in shots like those above, so we decided to use a mouse-over to better show how each setting compares to Off.)

Shadow Correction. As you can see from the thumbnails and histograms, there was a gradual lightening of shadows as the Shadow Correction setting was increased, while highlights remained roughly the same. If you look closely at the shadow detail, you will notice an increase in noise as the setting is turned higher, but that's to be expected and noise levels are still pretty low. The camera reported an ISO of 100 for all three settings of Shadow Correction.

Highlight Correction. Here, we can see that highlights were indeed dialed-back with Highlight Correction On versus Off.,while midtones and shadows remained roughly the same. The Pentax K-r boosted ISO to 200, so shadow detail was slightly noisier. (Click the link to see the full res image.)

Here are the results with our Far-field House shot. Again, we see a lightening of shadows as the Shadow Correction setting is increased, and a reduction in highlight clipping with Highlight Correction.

HDR Capture
The Pentax K-r offers a High Dynamic Range (HDR) capture mode where the camera takes three images (underexposed, normal, and overexposed) in quick succession and combines them in-camera into one image.  If performed properly, this method should result in much higher dynamic range, without the additional noise penalty that comes with boosting shadows or sensitivity when using the D-Range option. (In fact, it can reduce shadow noise by combining shadows from the overexposed shot.) There are six HDR settings available, three more than the K-x: Off (default), Standard, Auto and Strong 1/2/3. (The K-x has just one "Strong" setting, and no "Auto" setting.)

As you can see from the above images, HDR Standard and Auto settings worked quite well on our "Sunlit" Portrait test shot, reducing both clipped highlights and bringing out shadow detail. The Strong settings were a bit too much for this scene, resulting in very flat and unnatural looking images with reduced saturation. In addition to the additional levels compared to the K-x, the K-r has an Auto Align function which should let you shot HDR images without the use of a tripod, but we didn't test the effectiveness of that feature in the lab. Obviously, you'll want a static subject for this feature, so it's not really suited to portraits.

Dynamic Range
A key parameter in a digital camera is its Dynamic Range, the range of brightness that can be faithfully recorded. At the upper end of the tonal scale, dynamic range is dictated by the point at which the RGB data "saturates" at values of 255, 255, 255. At the lower end of the tonal scale, dynamic range is determined by the point at which there ceases to be any useful difference between adjacent tonal steps. Note the use of the qualifier "useful" in there: While it's tempting to evaluate dynamic range as the maximum number of tonal steps that can be discerned at all, that measure of dynamic range has very little relevance to real-world photography. What we care about as photographers is how much detail we can pull out of the shadows before image noise becomes too objectionable. This, of course, is a very subjective matter, and will vary with the application and even the subject matter in question. (Noise will be much more visible in subjects with large areas of flat tints and subtle shading than it would in subjects with strong, highly contrasting surface texture.)

What makes most sense then, is to specify useful dynamic range in terms of the point at which image noise reaches some agreed-upon threshold. To this end, Imatest computes a number of different dynamic range measurements, based on a variety of image noise thresholds. The noise thresholds are specified in terms of f-stops of equivalent luminance variation in the final image file, and dynamic range is computed for noise thresholds of 1.0 (low image quality), 0.5 (medium image quality), 0.25 (medium-high image quality) and 0.1 (high image quality). For most photographers and most applications, the noise thresholds of 0.5 and 0.25 f-stops are probably the most relevant to the production of acceptable-quality finished images, but many noise-sensitive shooters will insist on the 0.1 f-stop limit for their most critical work.

JPEG. The graph at right (click for a larger version) was generated using Imatest's dynamic range analysis for an in-camera K-r JPEG file with a nominally-exposed density step target (Stouffer 4110). At default settings and base ISO, the graph shows 10.7 f-stops of total dynamic range, with 7.15 f-stops at the High Quality level. These are good numbers, if not quite as good as recent competition. Compared to the Pentax K-x which uses the same or very similar sensor, the K-r produced almost identical results in both the High Quality level score (7.15 vs 7.18 f-stops), and total dynamic range (10.7 vs 10.6 f-stops). Compared to recent competitors, the Pentax K-r scored a little lower at the highest quality level, but that's likely in-part due to the K-r's slightly high default contrast and sharpening, which tends to amplify noise and reduce scores at the High Quality threshold.

RAW. The graph at right is from the same Stouffer 4110 stepchart image captured as a RAW (.DNG) file, processed with Adobe Camera Raw using the Auto setting. The Pentax K-r's RAW file scored just over an f-stop more in total dynamic range (11.8 vs 10.7 f-stops) and the score at the highest quality level increased over two f-stops from 7.15 to 9.33, which is very good. Again, results are very similar to those of the Pentax K-x, with the same High Quality score (9.33 f-stops) though with slightly higher total score (11.8 vs 11.4 f-stops). It's worth noting here is that ACR's default noise reduction settings reduced overall noise somewhat (see the plot in the lower left-hand corner) relative to the levels in the in-camera JPEG, which would tend to boost the dynamic range numbers for the High Quality threshold. Also, the extreme highlight recovery being performed by ACR here would likely produce color errors in strong highlights of natural subjects. Note that this measurement has a margin of error of about 1/3 f-stop, so differences of less than 0.33 can be ignored.

Low Light. The Pentax K-r performed reasonably well here, able to capture usable images down to the 1/16 foot-candle light level (about 1/16 as bright as average city street lighting at night), at all ISO settings. The K-r's metering system struggled a bit with getting the exposure correct at the lowest levels though, so we used manual exposure for these shots. Color balance with Auto white balance wasn't very consistent, sometimes having a magenta cast which often shifted to a blue or green cast at different ISOs and light levels. Noise was quite low up to ISO 1,600, and even at all but the highest ISOs there's still a lot of detail to work with when high ISO NR is set to "Off". The Pentax K-r gives you four options for high ISO noise reduction: Auto, Off, Low, Medium, and High, and you can choose the level of noise reduction for each ISO level, so you have a lot of flexibility in deciding how much noise to trade for detail. Except for the "No NR" shots in the table above, these were all shot using the default Auto NR settings. We did not notice any "hot" pixels except at very high ISOs and/or with NR turned "Off" where they are expected, nor did we detect any significant banding issues.

The Pentax K-r's phase-detection autofocus system was able to focus down to just above the 1/8 foot-candle light level with its AF assist light turned off, though it was able to focus in total darkness with the focus assist lamp enabled. In Live View mode with contrast-detect autofocus, the K-r was able to focus down to just above the 1/2 foot-candle, which is not as good as most SLRs in Live View mode. (Keep in mind that the longer shutter speeds here demand the use of a tripod to prevent any blurring from camera movement. A useful trick is to just prop the camera on a convenient surface, and use its self-timer to release the shutter. This avoids any jiggling from your finger pressing the shutter button, and can work quite well when you don't have a tripod handy.)

How bright is this? The one foot-candle light level that this test begins at roughly corresponds to the brightness of typical city street-lighting at night. Cameras performing well at that level should be able to snap good-looking photos of street-lit scenes.

NOTE: This low light test is conducted with a stationary subject, and the camera mounted on a sturdy tripod. Most digital cameras will fail miserably when faced with a moving subject in dim lighting. (For example, a child's ballet recital or a holiday pageant in a gymnasium.) Digital SLRs like the Pentax K-r do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.

Print Quality
ISO 100 to 400 images look great at 20x30 inches; ISO 3,200 shots print well at 13x19, and even ISO 25,600 shots make a good 4x6-inch print.

ISO 100 to 200 shots look great at 20x30 inches, with excellent detail and color.

ISO 400 images look good at 20x30, but some luminance noise creeps into the shadows. It becomes a non-issue when print size is reduced to 16x20 inches.

ISO 800 shots also look good at 16x20 inches, with some luminance noise, and minor loss of detail in low-contrast red areas.

ISO 1,600 images also look good at 16x20 inches, though there is some softening in detail overall, and the red leaf swatch continues to degrade. Reduction to 13x19 inches brings detail back to what can be called crisp.

ISO 3,200 images print well at 13x19, though luminance noise is a bit noisier. Detail remains pretty sharp, though, except for the red areas, which lose more detail than other areas.

ISO 6,400 images have good detail at 11x14 inches, but luminance noise is a bit rough in shadow areas, which warrants reduction to 8x10, where it's not bad at all.

ISO 12,800 shots again have good detail, but noisy shadows at 8x10. Reduction to 5x7 brings it back to an acceptable level.

ISO 25,600 shots look soft and untidy at 5x7, but look much better reduced to 4x6, though some of the colors lack detail thanks to a saturation boost.

Overall an excellent performance from the Pentax K-r.

Testing hundreds of digital cameras, we've found that you can only tell just so much about a camera's image quality by viewing its images on-screen. Ultimately, there's no substitute for printing a lot of images and examining them closely. For this reason, we now routinely print sample images from the cameras we test on our Canon Pro9000 Mark II studio printer, and on the Pixma MP610 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)