Pentax K100D Digital Camera Review

The Pentax K100D has a nearly complete range of manual controls. The user can set aperture, shutter speed, focus, ISO, white balance and parameters including saturation, sharpness and contrast. The controls aren't all convenient, but the only flat-out absence is a lack of white balance fine-tune.

 

The Pentax K100D's autofocus system is a particular strong point – or maybe 9 strong points. Pentax puts the same autofocus module in all its DSLRs. It consists of nine cross-type sensor sites, plus two conventional sites. Cross-type sites can sense focus in both horizontal and vertical detail. Of course, no sensor needs perfectly vertical or horizontal subject matter to focus, but typical sensors do better turned one way or the other with many subjects. Cross-type sensors find detail for focus in a wider array of subject textures than conventional ones.

 

Two factors limit a camera's ability to focus: overall brightness of the scene, and contrast in the subject. Autofocus systems can't handle subjects with no contrast at all. A clear, blue sky is a good example. And in very low light, cameras get less and less accurate.

 

We compared the Pentax K100D with the Nikon D2H and the Nikon D80, shooting scenes in a dimly-lit room, and shooting two targets we created in Adobe Illustrator. Aside from the fact that we had the two Nikons on hand, the reasons for choosing the D2H and the D80 are simple: the D2H was the first camera on the market with nine cross-type autofocus sensors, and it uses the same CAM-2000 autofocus module in the current D2X and D2Hs. The D80 uses a less-expensive 11-point module, with a single cross-type sensor in the middle of the frame. Our targets were rows of gray bars: dark gray bars on a black background, and pale gray bars on both a white and medium-gray background. This is not a standardized test. It was just an easy way to compare the cameras, with a clear idea of what they were focusing on. These tests do not measure focusing speed, which depends on lens mechanics.

 

The Pentax K100D did much better than the D80, though not quite as well as the D2H. The K100D's nine cross-points are all a little better than the D80's only cross-point, handling lower light better with low-contrast targets. Testing the K100D's standard points with the D80's standard points gave the same result – the K100D came out on top. The D2H handled the test better than the K100D, and it has another advantage. Its sensor sites are spread more widely across the frame.

 

It's a good thing that the Pentax K100D's autofocus is so good because its manual focus is nothing to write home about. The screen is dim, and the image looks small because the viewfinder has only a 0.85x magnification ratio. The autofocus system could handle much lower light than the manual system. Manual focus is enabled by flipping the focus switch on the side of the lens mount.

 

Exposure (8.75)
The Pentax K100D offers exposure compensation 2 EV above or below the meter reading, in 1/3-EV steps. That takes care of 90 percent of the compensation most users do, but some competing cameras offer up to 5 EV above or below. In manual mode, the K100D offers a clever option – pressing the auto-exposure lock button makes the aperture and shutter jump to the meter reading. It's an option that could speed up manual shooting in some situations.

Metering (8.0)
The Pentax K100D offers the standard three meter modes: Spot, Center-weighted Average and Evaluative. Spot metering measures a tiny area, about the size of an autofocus sensor site. Spot can be set so that it measures on the active AF site or just the center of the frame. Center-weighted takes a single reading, but it is more sensitive in the middle of the frame. It's a setting that some photographers like for landscapes. Evaluative metering takes several separate readings across the frame and uses a logic circuit to establish a proper reading. The Pentax K100D Evaluative system takes 16 readings, which is on the low end – some cameras sort through 256 measurements.

We found that the K100D's Evaluative system worked well in straightforward lighting situations – it's better than Center-weighted. Evaluative systems which are supposed to detect back-lighting and other high-contrast situations, and compensate for them. Like most other Evaluative systems, though, the K100D compromised too much in high-contrast settings, setting the camera to under- or overexpose the subject in order to maintain detail in the background. It got closer to the right exposure than Center-weighted, but in many situations, careful use of the Spot setting is the best choice.

White Balance (7.0)

The Pentax K100D doesn't allow white balance fine-tuning, a useful feature for JPEG shooters (as opposed to RAW shooters), especially in mixed or fluorescent lighting. The K100D's options are comparable to many point-and-shoots. It offers an Auto setting, and presets for Daylight, Shade, Cloudy, Tungsten, Flash and three types of Fluorescent tubes. It also offers manual white balance, which saves a single white balance reading that the user can set by photographing a white target. The K100D adds the option of taking the manual balance from the whole image or just a small area at the center of the frame. White balance options are one of the K100D’s weak points.

ISO (7.0)

The Pentax K100D's ISO range runs from 200 to 3200, plus Auto. ISO shifts in full-EV steps, which is less convenient and flexible than the 1/3-EV increments most DSLRs offer. The user can limit the Auto ISO range to 200—800 or 200—1600. The K100D can also show a warning when the ISO hits 400, 800, 1600 or 3200. Our image quality tests show that the K100D takes a big quality hit in every parameter at ISO 3200, it just may get a picture that no other option would.

Shutter Speed (7.5)

With shutter speeds from 30 seconds to 1/4000, plus B for time exposures, the K100D's shutter doesn't impose any practical limit on shooting. The speed is set steplessly in Program and Aperture priority modes, and in 1/3-EV increments when set manually. Its maximum flash sync of 1/180 is a disappointment. Given its minimum ISO of 200, the sync speed limits outdoor fill flash to small apertures and very bright flashes.

Aperture (0.0)

The Pentax K100D controls aperture electronically. The 18-55mm kit lens has a variable maximum aperture of f/3.5 to 5.6. That's very limiting for indoor, available-light photography. F/5.6 yields too much depth of field for portraiture. The minimum aperture we could get was f/38, which is too small for a lens of this focal length – diffraction will harm image quality at that setting. Pentax offers much better lenses, including two wider-aperture optics at about the same focal range. It might make sense to buy the K100D with a top-quality lens, rather than the K10D with a mediocre one.

 

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