Pentax K-7 Image Quality

Saturation & Hue Accuracy
Bright, intense colors with moderate oversaturation of strong blues, reds, and greens.

Saturation. The Pentax K7's default settings push most colors by quite a bit, especially blues, greens, and some reds. Overall, images were very bright and punchy, with color that was a little over the top for a prosumer SLR. You can, however, always 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 K-7 lean toward the warm side, but many consumers prefer the "healthier" appearance of warmer skin tones. 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. The Pentax K7 showed a few color shifts relative to the correct mathematical translation of colors in its subjects, but had pretty good accuracy overall. Most noticeable was a shift in orange toward yellow, with some shifts in cyans, blues, and reds as well. Hue is "what color" the color is.

Saturation Adjustment
The Pentax K-7 has a total of nine saturation settings available, four above and four below the default saturation. This covers a pretty wide range of saturation levels, about as wide a range as you're likely to find photographically relevant, apart from special effects that are arguably better achieved in software. The fine steps between settings mean you can program the camera to just the level of saturation you prefer.

The table above shows results with several saturation settings. Click on any thumbnail above to see the full-sized image.

Exposure and White Balance

Indoors, incandescent lighting
Warm results with Auto and 2,600 Kelvin, slightly cool with Incandescent, though good color with Manual white balance setting.

Indoors, under normal incandescent lighting, color balance was quite warm with the default Auto white balance setting, with a fairly strong orange cast; however, this is considerably better than Pentax SLRs used to produce which was a bright yellow/orange cast. The Pentax K-7 features a new "Automatic White Balance in Tungsten" setting in Custom menu 12. Options are "Subtle" and "Strong" correction, with the default being Subtle. The Strong setting resulted in a reduced orange cast compared to Subtle, with a slightly magenta tint. Results with the Incandescent setting were a bit on the cool side, with a slightly bluish cast. The 2,600 Kelvin setting resulted in a slightly warm cast, but wasn't too far off. The Manual setting was the most neutral and accurate. Note that there is also a new Color Temperature Enhancement (CTE) white balance mode, which strongly intensified the orange/yellow cast in our indoor test shot. The Pentax K-7 required slightly higher than average amount of positive exposure compensation for our indoor scene, at +0.7 EV. Overall color with the Manual white balance setting looks quite good, though the blue flowers appear slightly purple. (Many digital cameras reproduce these flowers with a dark, purplish tint, so the Pentax K-7 actually performs a little better than average here.) Our test lighting for this shot is a mixture of 60 and 100 watt household incandescent bulbs, a pretty yellow light source (2,600 Kelvin), but a very common one in typical home settings here in the U.S.

Outdoors, daylight
Bright colors overall, though a tendency toward a warm cast and slightly high contrast under harsh lighting.

Outdoors, the Pentax K-7 performed fairly well, requiring slightly higher than average exposure compensation of +1.0 EV for our "sunlit" portrait shot to keep the face reasonably bright. That's not bad, since the average among the cameras we tested is +0.7 EV. Contrast is a little high, as you might expect under such harsh lighting, and highlights in the model's shirt and flowers are clipped, but there's plenty of detail in the deep shadows. The highlights were blown out just a bit in the House shot, but not too badly. Color balance is good as well, though saturation is a little high. Overall, good performance here.

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

Resolution
High resolution, 1,700 ~ 1,800 lines of strong detail.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,800 lines per picture height in the horizontal direction, and about 1,700 in the vertical direction. Extinction didn't occur until around 2,600 to 2,800 lines. We weren't able to do much better with Adobe Camera RAW processed RAW files, though results were crisper, with fewer moire interference patterns near or above the resolution limit (see other areas of the resolution target). 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 minor edge-enhancement on high-contrast subjects. Minimal noise suppression visible.

Sharpness. The Pentax K-7 produced sharp images with good detail. Some edge enhancement artifacts are visible on high-contrast subjects such as the crop above left, but overall results are still good. Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.

Detail. The crop above right shows only minimal 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 deepens. Still, it's a great performance, as most SLRs have quite a bit more trouble with the straight, red strands of hair 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-7 does a pretty good job at balancing between sharpness and visible sharpening artifacts in camera JPEGs. A little more detail can be obtained from carefully processing RAW files, though, without 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. Examples include in-camera Super Fine JPEG, and RAW (.DNG) file processed through Adobe Camera Raw version 5.4, then sharpened in Photoshop. For the Pentax K-7's images, I found best results with strong but tight 300% unsharp masking with an 0.3 pixel radius. As you can see, the ACR conversion extracted a touch more detail than the JPEG, but the camera is doing a pretty good job at preserving fine detail in JPEGs to begin with.

ISO & Noise Performance
Low noise at the normal sensitivity settings, with very good results up to ISO 800. Higher noise at 1,600 and above.

The Pentax K-7 produced low noise at its lower sensitivity settings, and even at ISO 400, noise is fairly low, with little detail lost to the noise reduction. (This comes as no surprise, since the K7's default noise reduction doesn't kick in until ISO 800.) At ISO 800, noise pixels are more evident but are very fine-grained. There's some chroma noise visible in the shadows, but there's still plenty of detail overall. ISO 1,600 continues the trend, with more obvious "grain" and some blurring, but there's still quite a bit of fine detail left. At the higher settings of 3,200 and especially 6,400, noise levels are much higher, with heavy blurring and chroma noise blotches. Color balance also shifts towards green at ISO 6,400. See the Print Quality section below for recommended maximum print sizes at each ISO.

Extremes: Sunlit and low light tests
High resolution with strong overall detail, but slightly high contrast with strong highlights. Very good low-light performance, capable of capturing bright images under average city street lighting and much darker conditions.

Sunlight. The Pentax K-7 produced slightly high contrast with some washed-out highlights and deep shadows under the harsh lighting of the test above, but performed better than many SLRs in this regard. Shadow detail is pretty good, despite some minor image noise. Our outdoor target required +1.0 EV exposure compensation for a reasonably bright face, which is a little higher than average. Some may prefer the +1.3 EV exposure, but we thought too many highlights were blown, and the skin tone was washed out. Be sure to use fill flash in situations like the one shown above; it's better to shoot in the shade when possible.

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.)

Contrast Adjustment
We really like it when a camera gives us the ability to adjust contrast and saturation to our liking. It's even better when those adjustments cover a useful range, in steps small enough to allow for precise tweaks. Just as with its saturation adjustment, the Pentax K-7's contrast setting meets both challenges, though it could have used slightly more range on the minus side.

At its lowest contrast setting, the Pentax K-7 did an okay job of preserving highlight detail, maintaining fairly natural-looking skin tones, and holding nice detail in the shadows. There are still some blown highlights, but fewer than at default contrast. The Pentax K-7 captures natural looking color outdoors, though just slightly on the warm side. Overall, good results here, especially when the contrast setting is tweaked, though colors are a bit flat.

The series of shots above shows results with several different contrast adjustment settings, showing every other step, as well as the default and both extremes. 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. The Pentax K-7s contrast adjustment worked well, however it had quite an effect on color saturation. Contrast and saturation are actually fairly closely coupled, so this is unfortunately not unusual.

D-Range Settings
The Pentax K-7 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 detail while attempting to keep highlights and midtones as they are, and likewise, Highlight Correction attempts to reduce highlights without darkening shadows and midtones. See the images and crops below to see their effect on our high contrast "Sunlit" Portrait test shot.

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. 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. It's interesting that the camera reports an ISO of 100 for all three settings of Shadow Correction.

In the crops above, we can see that shadow levels are virtually untouched, (perhaps just slightly boosted when On), while more highlight detail is preserved with Highlight Correction On (right) than it is with it Off (left). Again, if you look closely at the shadow areas, there is an increase in noise, but this time the K-7 reports ISO 200 was used.

Above, we see similar results for our Far-Field House shot. Note that Shadow and Highlight Correction are independent settings found in the Record Mode 1 menu, and can both be enabled at the same time.

HDR Capture
The Pentax K-7 has 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 sensitivity when using the D-Range option. (In fact, it can reduce shadow noise by combining shadows from the overexposed shot.) There are three HDR settings available: Off (default), Standard and Strong.

As you can see from the above images, it didn't work very well for our "sunlit" portrait shot, resulting in very flat and unnatural looking images with reduced saturation. It did a good job of bringing out shadow detail, but even the lowest "Standard" setting was too strong for the highlights, turning white into grey. The Pentax K-7's HDR mode may work better with a different subject such as a landscape with a bright (normally washed-out) sky. It probably isn't designed to work with portraits anyway, as subject motion would likely be a problem.

Face Detection
The Pentax K-7 has a face-detection AF/AE option in Live View mode.

As you can see above, it does improve the exposure over the default without using any exposure compensation, but the model's face is still very dim.

Low light. The Pentax K-7 performed well on the low-light test, capturing usable images at the lowest light level with the lowest sensitivity setting (ISO 100). Low light exposure metering is very good, as can be seen by the consistent exposures and fairly regular progression of shutter speeds. Chroma noise is a little high above ISO 800, but reasonable for a subframe SLR. There are a few hot pixels at all levels and ISOs, increasing in number as light levels drop and ISOs increase. There are hints of horizontal banding at higher ISOs, but it's not really noticeable. Color balance was pretty neutral, if just slightly cool with the Auto white balance setting.

The camera's phase-detect autofocus system was able to focus on the subject down to just past the 1/8 foot-candle light level unassisted (and in complete darkness with the AF assist enabled). Surprisingly, contrast-detect autofocus during Live View mode was able to focus down past our lowest level of 1/16 foot-candle unassisted. It wasn't fast, but it kept trying until it eventually focused successfully.

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-7 do much better than point & shoots, but you still shouldn't expect a quick autofocus lock with moving subjects.

Print Quality
Great print quality, good color, sharp 13 x 19-inch prints.

The Pentax K-7's printed output is really impressive, able to output usable 16 x 20-inch prints at ISO 100, straight from the camera. They're slightly soft, but really quite good; a little sharpening in a program like Photoshop could make them just fine at this size. 13x19-inch prints are sharper. ISO 200 shots print the same as 100, producing a good 16x20 or great 13x19. ISO 400 images do just fine at 16x20, and of course are better 13x19 and 11x14, but not by much. ISO 800 shots look astonishingly good at 13x19, with some chroma noise in the shadows that's not very noticeable. This gets better at 11x14. Some detail is lost at ISO 1,600, but the Pentax K-7's image is still usable at 11x14. ISO 3,200 images are better at 8x10, and ISO 6,400 images are decent at 5x7, despite the grainy shadows. A very impressive performance from the Pentax K7!

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 (older) Canon iP5200 here in the office. (See the Canon Pixma Pro9000 Mark II review for details on that model.)