Pentax K-01 Exposure

Saturation & Hue Accuracy
Most colors are highly saturated at default settings, with about average hue accuracy.

Saturation. The Pentax K-01's default image tone setting of "Bright" pushes most colors by quite a bit at base ISO, especially blues, greens, and reds. Overall, images were very bright and punchy, with color that was a little over the top, but typical for Pentax. Saturation remains higher than average throughout the ISO range. You can of course always select a different image tone preset and/or turn down 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-01 were a touch yellow using auto white balance, while manual white balance produced a more pinkish, "healthier" appearance. 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. With an mean "delta-C" color error of 5.63 after correction for saturation, the Pentax K-01's overall hue accuracy was about average for a compact system camera. Most noticeable were moderate shifts in orange toward yellow and cyan toward blue, with minor shifts and some reds, yellows, and greens. (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.) Hue is "what color" the color is.

Saturation Adjustment
The Pentax K-01 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 including both extremes. See the Thumbnails index page for more (look for the files named K01OUTBSATx.JPG). Click on any thumbnail above to see the full-sized image.

Exposure and White Balance

Indoors, incandescent lighting
Very warm results with Auto white balance and too cool with Incandescent, but good color with Manual white balance setting. Average exposure compensation required.

The Pentax K-01's Auto White Balance had a difficult time with the very warm color balance of the household incandescent bulbs used in this shot, though there is an option to increase the color correction in AWB mode to "Strong" (default is "Subtle Correction"). Results with the Incandescent setting were too cool with a blue tint. The Manual setting produced the most accurate color balance, though a touch yellow. Note that a Color Temperature Enhancement (CTE) white balance option is also available (not shown), which exaggerates the temperature of the ambient light. The Pentax K-01 required an average amount of exposure compensation of +0.3 EV for this shot.  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 colors with very good exposure and good highlight/shadow detail preservation.

The Pentax K-01 handled tough outdoor lighting under harsh sunlight pretty well, producing bright colors with good exposure. Default contrast was on the high side (as most users prefer), resulting in some clipped highlights in the model's shirt and some of the flowers, as well as some lost shadows in the flowers and the background, though remaining shadow detail is unusually clean as we found with the K-5. +0.3 EV exposure compensation was required to keep the model's face reasonably bright, which is better than the average of +0.7 EV usually required for this scene. Skin tones were just a touch yellow using auto white balance, so we preferred manual white balance for outdoor portraits. Our Far-field shot was well exposed at 0 EV, again with bright colors. Very few highlights were clipped, while shadow detail was quite good. Very good results overall here.

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

Resolution
Very high resolution, ~2,100 lines of strong detail from JPEGs, about the same from converted RAW files.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 2,100 lines per picture height in both the horizontal and vertical direction in JPEGs. Complete extinction didn't occur until around 2,800 lines in both directions. We weren't able to extract any more resolution from RAW files processed through Adobe Camera Raw in this high-contrast target, though complete extinction of the pattern extended to around 3,000 lines. The ACR processed RAW images didn't show as many jagged edges on fine diagonal lines as the camera JPEGs did, though color moire was higher. 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
Sharp images overall, though moderate edge-enhancement on high-contrast subjects. Minor noise suppression visible at base ISO.

Sharpness. The Pentax K-01 produced sharp images with very good detail at default settings. Some edge enhancement artifacts are visible on high-contrast subjects such as the sharpening halos around thicker branches and the pine codes in the crop above left, but overall results are still good (albeit with a bit too much contrast and saturation for our tastes). 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 only minimal detail loss due to noise suppression, as the darker areas of the model's hair show a lot of detail. Individual strands are still distinguishable even in the lighter shadows, though they begin to merge as shadows deepen, and in places where the tone and color of adjacent strands is very close. Very good performance here. 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.

RAW vs In-Camera JPEGs
As noted above, the Pentax K-01 does a pretty good job at capturing lots of detail, but more detail can be obtained from carefully processing RAW files, without introducing additional 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 Best quality JPEG as well as the matching RAW file processed through Adobe Camera Raw (ACR) version 6.7, then sharpened in Photoshop. For the Pentax K-01's RAW files, we found best results with strong but tight 450% unsharp masking with a 0.3 pixel radius.

As is frequently the case, the demosaicing and sharpening in Adobe Camera and Photoshop deliver finer detail than the camera. Looking very closely at the images, ACR extracts quite a bit more detail that wasn't present in the JPEGs, but there's also a bit more noise visible. You can always adjust noise reduction to your liking, though, which is one of the advantages of shooting RAW and processing the images yourself.

ISO & Noise Performance
Very good handling of noise versus detail to ISO 1,600.

The Pentax K-01's images were very clean at ISO 100 through 800, which just a touch of luminance noise becoming more visible in the shadows and darker midtones as ISO increases. Detail was still very good at ISO 1,600, with a tight film-like noise "grain" and very little fine detail lost to noise reduction. At ISO 3,200, there's increased blurring and more visible noise "grain", but fine detail is still generally quite good, though subtle detail in reds take a larger hit. ISO 6,400 shows stronger luminance and chrominance noise as well as increased blurring, though there's still a fair amount usable detail left. As expected, images at ISOs 12,800 and 25,600 are noticeably noisier and less detailed than those at lower sensitivity levels, and chroma noise in the form of purple and yellow blotching is quite strong at ISO 25,600.

Default noise reduction seems stronger than the K-5's, but otherwise image quality appears to be similar which is to say very good. Note that these images were shot using the Pentax K-01 "Auto" noise reduction setting. The Pentax K-01 offers an unusually flexible amount of control over noise reduction applied to its JPEGs. In addition to "Auto", you can adjust how much NR is applied ("Off", "Low", "Medium" or "High") at all ISOs, or you can select "Custom" which allows you to choose from the same four options at each ISO sensitivity setting (in whole EV increments). Of course, the impact of noise and detail loss are highly dependent on the size the photos are printed at, and pixel-peeping on-screen has surprisingly little relationship to how the images look when printed: 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
Very high resolution with very good highlight and shadow detail. Very good low-light performance, capable of capturing bright images in near darkness, though autofocus really struggled in low light.

Sunlight:
The Pentax K-01 handled the deliberately harsh lighting very well in the above test. Though default contrast is quite high, highlight and especially shadow detail are very good. (The K-01's contrast adjustment also did a good job of decreasing overall contrast though it did impact saturation; see the section below.) The +0.3 EV exposure did the best job here, as we thought that too many highlights were lost at +0.7 and 0 EV was a tad dim in the face. Some highlights were blown in the model's shirt and bright flowers at +0.3 EV, but not as many as we're used to seeing, while very good detail was preserved in the shadows with unusually low levels of noise. Note that these shots were captured with the Pentax K-01's D-Range control set to "Off."

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.)

Dynamic Range Analysis
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 Pentax K-01 JPEG file with a nominally-exposed density step target (Stouffer 4110). At the base ISO of 100 (the optimal ISO), with D-Range Expansion set to Off and default Contrast, the graph shows 10.6 f-stops of total dynamic range, with 7.73 f-stops at the "High" Quality level. These are are good results for an APS-C model. Compared to the Pentax K-5, the K-01 actually scored a bit better with its JPEG producing 7.73 versus 7.22 f-stops at the highest quality level, and 10.6 vs 10.5 f-stops total dynamic, though some of that improvement in the high quality number is due to slightly stronger default noise reduction. Note though that this measurement has a margin of error of about 1/3 f-stop, so differences of less than 0.33 can be ignored.

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. As can be seen, the score at the highest quality level increased just over 2 f-stops from 7.73 to 9.74 f-stops, while total dynamic range increased just over one f-stop from 10.6 to 11.7. These results are good, though not as good as the K-5 which managed 10.5 f-stops at the highest quality level, though total dynamic range was similar at 11.7 f-stops versus the K-5's 11.5. It's also 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 higher quality thresholds.

Contrast Adjustment
Just as with its saturation adjustment, the Pentax K-01'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-01 did a really excellent job of bringing nice detail out of the shadows as well as preserving 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 shot were noticeably less saturated.

The series of shots above shows results with several different contrast adjustment settings, showing the minimum step size around the default, as well as both extremes. 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.

D-Range Settings
The Pentax K-01 offers three Shadow Correction levels (Low, Medium, and High, plus Off and Auto) as well as one Highlight Correction level (Auto/On/Off). Auto is the default setting for both. 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 affects 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. Above, we see a gradual lightening of shadows as the Shadow Correction setting is increased, but there is also a slight increase in highlight clipping with the Auto setting. 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 reports an ISO of 100 for all three settings of Shadow Correction.

Highlight Correction. Highlight Correction set to On did reduce the number of bright highlights, but it raised ISO to 200. Auto decided no highlight correction was necessary, producing results practically identical to Off.

Here are the results with our Far-field shot. Again, we see a lightening of shadows as the Shadow Correction setting is increased. Highlight Correction worked as expected though there weren't many highlights clipped in the first place, so again, the Auto setting had little effect.

HDR Capture
The Pentax K-01 has a High Dynamic Range (HDR) capture mode where the camera takes three images (underexposed down to -3 EV, normal, and overexposed up to +3 EV) 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 sensitivity. (In fact, it can reduce shadow noise by combining shadows from the overexposed shot.) There are four HDR settings available, one less than the K-5: Off (default), Auto, and HDR 1/2/3.

The lowest manual HDR setting worked reasonably well on our Far-field test shot, reducing both clipped highlights and bringing out shadow detail. Higher settings were too much for this scene, resulting in very flat and unnatural looking images with strong halos, and the Auto setting decided HDR wasn't required for this shot. As with most HDR systems, watch out for the ghosting that occur when subjects are moving between exposures. The K-01 has an Auto Align function which should let you shot HDR images without the use of a tripod, but we didn't test that feature in the lab.

Low Light. The Pentax K-01 performed 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-01'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 was pretty good even at lower light levels, with just a slightly cool bias. At very high ISOs, chroma noise shifted overall color balance, sometimes towards magenta or green.

Noise was quite low up to ISO 1,600, and even a higher ISOs there's still a lot of detail to work with especially when high ISO NR is set to "Off". As mentioned previously, the Pentax K-01 gives you four options for high ISO noise reduction: Auto, Off, Low, Normal, and High, and you can choose the level of noise reduction for each ISO, 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.

There are a few hot pixels that become more visible as light levels fall at lower ISOs, but the K-01 does have a pixel mapping feature that should correct for those. We did not detect any banding issues except for a hint of horizontal banding at very high ISOs.

The Pentax K-01's contrast-detection autofocus system was only able to focus on the subject down to just below the 1/2 foot-candle light level using an f/2.8 lens with its AF assist light turned off. This is poor performance compared to most SLRs and even most CSCs. The camera was however able to focus in total darkness with the focus assist lamp enabled.

(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.) Thanks to their larger sensors, compact system cameras like the Pentax K-01 tend to do better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects. (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.)

Print Quality
Good color and detail at ISO 100, easily making 20 x 30-inch prints; ISO 3,200 images make a good 13 x 19-inch print; ISO 25,600 shots are good for a 5x7.

ISO 80 looks very crisp at 20x30 inches, with good color and detail.

ISO 100 images looked pretty good printed at 20 x 30 inches with good color and detail overall.

ISO 200 shots also looked good at 20 x 30.

ISO 400 images looked better at 16 x 20.

ISO 800 images had sufficient detail for 16 x 20, but reds were slightly softer, particularly our red leaf fabric swatch. Just a hint of luminance noise dances in the shadows.

ISO 1,600 shots had sufficient detail for 16 x 20 inches, though reds were blurrier (a very common outcome).

ISO 3,200 shots were good printed at 13 x 19 inches, though color was noticeably faded, with a very blurry red leaf swatch, which we'll stipulate from here on out.

ISO 6,400 shots were usable at 11 x 14, but looked better at 8 x 10.

ISO 12,800 files still looked good at 8 x 10.

ISO 25,600 images made a good 5x7.

Overall, a very good performance from the Pentax K-01. Shadow noise was well-controlled throughout the series at the sizes stated, which can be really distracting on other cameras.

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.)