Pentax K100D Exposure

Saturation & Hue Accuracy
Slightly high saturation overall, though still pleasing results. Generally good hue accuracy.

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. The Pentax K100D actually oversaturates color in a few areas, though cyans seem to be in check. Still, overall saturation was quite pleasing, and the camera does offer a five-step saturation adjustment. 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. In this case, the K100D did produce slightly warm skin tones, but many consumers prefer the "healthier" appearance of warmer skin tones.

The other important part of color rendition is hue accuracy. Hue is "what color" the color is. The Pentax K100D often produced a slightly warm color balance, particularly with the Auto white balance setting. It also pushed yellow slightly toward green, and reds toward orange, but overall results were still quite good.

Exposure and White Balance

Indoors, incandescent lighting
Auto White Balance does not compensate for tungsten lighting at all. Good color with the Manual white balance setting, though just a hint warm. A little more positive exposure compensation required than usual.

Color balance indoors under incandescent lighting was pretty warm with the Auto white balance setting, though the Manual and Incandescent options both produced more accurate results. In the end, the Incandescent setting was just a hint too warm, though the Manual option was also on the warmer side. The Pentax K100D required a little more than the average amount of positive exposure compensation here, at +1.3 EV. Despite the slight warm cast, overall color with the Manual white balance setting is quite good, though the blue flowers appear very purple. (Many digital cameras have trouble here.) 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 overall, though a tendency toward a warm cast and high contrast under harsh lighting. About average exposure accuracy.

Outdoors, the Pentax K100D tended toward a warmer color balance, though overall color was generally pretty good. The K100D performed about average in terms of exposure, requiring the typical amount (or slightly less) of positive compensation we're accustomed to seeing among consumer digital cameras. The K100D's default contrast is a little high, producing washed-out highlights and dark shadows under the deliberately harsh lighting of our "Sunlit" portrait test shown above right. The camera's contrast setting does tame the highlights and shadows slightly, but the overall effect is a slightly dimmer image.

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

Resolution
High resolution, 1,100 ~ 1,200 lines of strong detail.

Our laboratory resolution chart revealed sharp, distinct line patterns down to about 1,200 lines per picture height horizontally, and only to about 1,100 lines vertically, again with the Pentax K100D's kit lens. Extinction occurred at around 1,700 lines. 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. Beware that while you might be able to make out what looks like distinct lines at numbers higher than those we've mentioned here, the camera is just doing its best to continue interpreting the lines. If you zoom in and follow them from the wider portions, you'll see the lines converge and reappear several times, so the lines you see at 1,600 and higher are really only artifacts generated by the camera's imaging system.

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

Sharpness & Detail
Reasonably sharp images overall, though slight edge-enhancement on high-contrast subjects. Some noise suppression also visible in the shadows.

The Pentax K100D captures fairly sharp images overall, though some edge enhancement artifacts are visible on high-contrast subjects such as the crop above left. (Edge enhancement creates the illusion of sharpness by enhancing colors and tones right at the edge of a rapid transition in color or tone.)

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. The crop above right shows some moderate noise suppression in the darkest areas of Marti's hair, though quite a few individual strands are visible in the lighter shadows.

ISO & Noise Performance
Low noise at the normal sensitivity settings, though a big jump in noise with strong blurring at the highest settings.

Noise levels are quite low at the Pentax K100D's lower sensitivity settings, with only moderately high noise at the ISO 800 setting. Noise increases at the 1,600 and 3,200 settings quite a bit, with much stronger blurring, though results aren't surprising at such high sensitivity settings.

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

Sunlight:
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.)

The Pentax K100D produced high contrast with slightly washed-out highlights and deep shadows under the harsh lighting of the test above. However, shadow detail is pretty good, despite some noise suppression and bright-pixel image noise. Though some areas look a little hot at +0.3 EV, I preferred it to the image at +0.7 EV, which had too many blown highlights for my preference. (In "real life" though, be sure to use fill flash in situations like the one shown above; it's better to shoot in the shade when possible.) The camera's contrast adjustment does help tame the high contrast here, but overall results are just slightly dim.

Low light:
The Pentax K100D captured bright 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 Auto white balance setting produced a fairly strong red color cast, which increased with the exposure time. At the camera's lower ISO settings, the Noise Reduction option did a fairly good job of eliminating bright pixel noise. However, at the other end, at ISO 3,200, noise levels don't differ strongly between the two shots. Though some bright pixels are eliminated, the overall effect of noise is about the same at the highest settings. The camera's autofocus system was able to focus on the subject down to well below the 1/16 foot-candle light level unassisted, which works out well for its exposure system. Do keep in mind though, that the very long shutter times necessary here absolutely demand the use of a tripod or other camera support to get sharp photos. (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.)

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.) For such applications, you may have better luck with a digital SLR camera, but even there, you'll likely need to set the focus manually. For information and reviews on digital SLRs, refer to our SLR review index page.

Print Quality
Excellent print quality, great color, good 11x14 inch prints. ISO 1600 images are soft but usable at 8x10, and ISO 3200 shots are still decent at 8x10 and quite excellent at 5x7.

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 i9900 studio printer, and on the Canon iP5200 here in the office. (See the Canon i9900 review for details on that model.)

With the Pentax K100D, we were pleasantly surprised across the board. At 13x19, its prints were slightly soft, but quite good for wall or table display. At high ISO, image noise levels are held in check quite well up to the maximum of ISO 3200! We almost never say that. ISO 800 shots under daylight-balanced lighting look quite good at 11x14 and, those shot under incandescent lighting remain usable out at 8x10, where images from most cameras will start to fall apart (the very warm color balance of incandescent lighting forces the camera's already-noisy blue channel to work harder, producing higher noise.) Though they were somewhat noisy, even our severe incandescent test produced usable images up to 8x10 at ISO 1600, so long as we printed only the manual while balanced images (as we mention further up, the Auto White Balance's performance indoors with incandescent is the K100D's main shortcoming). ISO 800 images can survive the enlargement to 11x14 quite well. For a six megapixel sensor, the K100D holds its own.