In true contrarian style, the K100D is the more expensive of the two, thanks to Pentax's own sensor-shifting optical image stabilization. Aside from that, the two SLRs are identical. Both feature 2.5-inch LCD screens, 11-point autofocus, and sensitivity as high as ISO 3,200; and they accept the legions of Pentax lenses, including fully manual lenses dating back further than the K1000. The unwashed, pixel-obsessed masses will no doubt complain about the 6.1-megapixel CCD sensor, but it's still more than enough for letter-size prints, which should be plenty for most casual shooters. Plus, at this price, it's one of the best bargains in the dSLR market. Based on the body of the *ist DS2, the K100D will feel familiar to current Pentax dSLR owners. Frequently accessed features, including ISO, flash, white balance, and drive mode can be found by pressing the function button, while you can access setup functions with the menu button. A mode dial on the left of the camera top lets you switch shooting modes or select from six scene modes. A choice marked SCN on the dial offers access to another eight scene modes, each with its own explanation.
Only one other dial adorns the body and is used to adjust exposure compensation or aperture or shutter speed in their respective priority modes. That means you have to hold a small button next to the shutter to change the aperture when shooting in full manual mode. This isn't as convenient as some cameras, which include two such dials: one for aperture and one for shutter speed. The same small button doubles as exposure-compensation access when shooting in any of the other modes.
A slider switch on the bottom-right of the camera back lets you turn image stabilization on or off and joins the menu button, four navigation buttons, and a function button to the right of the 2.5-inch 210,000-pixel LCD screen. The only other change from the *istDS2 is the eye cup, which is more squared, more difficult to remove, and thus less-prone to loss. It's a minor but welcome change.
Four AA or two CR-V3 batteries power the camera and load into the grip from below. Images are stored to SD cards. With a nice combination of auto and manual features, the Pentax K100D offers enough features to quench both experienced and amateur photographers. For the inexperienced, the Auto Pict. mode takes care of everything for you, while a healthy array of scene modes let you tackled specialized situations as you would with a digital compact or point-and-shoot. Program, aperture- and shutter-priority, manual, and bulb modes offer all the options experienced shooters want.
Possibly the biggest new feature in the K100D is its sensor-shifting shake reduction system. Sensors inside the camera detect any shake in the camera body, such as that caused by your caffeine-addled hands, and move the CCD sensor to compensate for those vibrations. Pentax claims its shake reduction will give you approximately 2 stops leeway in exposure, meaning you should be able to halve your shutter speed twice below your typical slowest comfortable shutter speed and still shoot reasonably sharp images. In our field tests, we found that the shake reduction in the K100D gave us between 1.5 and 2 stops leeway.
Pentax's 11-point through-the-lens (TTL) autofocus system is the same as that of the *ist DS2. It defaults to auto, but you can also manually select a point, or set it to center spot. Plus, you can choose from single, which locks and holds when you hold the shutter down halfway, or continuous, which keeps adjusting focus on your subject until you trip the shutter. The latter comes in handy when shooting skittish children or pets. The camera has a 16-segment TTL metering system with multipattern, center-weighted, or spot options and can be set to lock with focus or continue to meter until you shoot. Exposure compensation provides as much as plus or minus 2EV of leeway to tweak the camera's automatic exposure decisions.
One of the more interesting new features is digital preview. When you slide the power switch past On to the aperture blade icon, you can get either a digital or optical preview of the depth of field (DOF). The default is digital, which snaps a picture and displays it on the LCD but doesn't save it to the SD card. If you'd rather see a DOF preview through the viewfinder, you can switch to that more traditional method using one of the camera's custom settings. We're perplexed as to why one would want to preview DOF on the LCD rather than the viewfinder, but you never know when it might come in handy. Incidentally, this feature was included on the *ist DL2, which Pentax never released in the United States, but which Samsung sells under the GX-1L moniker.
Like the *ist DS2, the built-in pop-up flash has a guide number of 15.6 at ISO 200, but the angle-of-view coverage has been widened to 18mm to match the widest angle-of-view of the lens included in the kit version: the Pentax DA 18mm-to-55mm (35mm equivalent) f/3.5-to-f/5.6 zoom lens. It's a bit slow at the telephoto end but is similar to many of the kit lenses at this price level. The camera's flash sync speed is 1/180 second; again, what you'd expect for the money. While in most cases the Pentax K100D improves on the company's previously best-performing camera, the *ist DS2, the one place it loses ground is at start-up. It's still very impressive though, powering up and capturing its first JPEG or raw image in 1.2 seconds and subsequent images at 0.5-second intervals without flash, slowing noticeably to 1.7 seconds between shots with the pop-up flash turned on. Shutter lag measured 0.4 second in our high-contrast test and 1.3 seconds under low-contrast conditions.
Autofocus was quick to focus in most conditions, though did fail in some very low-light surroundings. That comes as no surprise, since, like Sony's Alpha DSLR-A100, the K-100D's AF system is rated to work down to only 1EV. Also, since there's no AF assist lamp, such as the one on the Sony, you'll have to take your chances with manual focus in lower light.
Shooting in continuous mode, you can shoot as many as five images before the buffer fills. In our lab tests, we captured five images in 1.6 seconds regardless of image size, for an average of 3.13fps. We were impressed with the Pentax K100D's image quality. Colors were well saturated with pleasing skin tones. Images had plenty of detail. We were able to see the stitching in our friends' shirts and individual strands of hair on their lovely heads. Edges were sharp but not overly sharpened, and there was plenty of detail in shadows without sacrificing detail in highlights.
Automatic white balance captured warm images with our lab's tungsten lights. Appropriately, the camera's tungsten setting fared best with these lights, while the manual white-balance setting came a close second, yielding slightly greenish results. In natural daylight, the automatic white balance did a fine job of producing neutral-looking colors.
The camera's lowest sensitivity setting is ISO 200. At this point, most dSLRs start out at ISO 100, so we were a little surprised that Pentax didn't extend the camera's range this time out. However, the camera does stretch all the way up to ISO 3,200 on the high end, and Pentax doesn't mince words--or in this case, numbers--by calling it a boost mode, or something of that ilk. Images were very clean at ISO 200 and ISO 400, and while speckles of noise appeared at ISO 800, it wasn't enough to lose any fine detail. Noise was obvious at ISO 1,600, but we still saw only a very slight loss of detail, and the noise was akin to a very fine but noticeable film grain. By ISO 3,200, noise grew appreciably and took on the colored-speckle look of digital noise. There was noticeable loss of detail, but we were surprised by how much detail remained. Images at ISO 3,200 were definitely usable, though probably better printed at less than full size.
Pentax's K100D does a wonderful job of balancing the needs of amateur and experienced photographers. It doesn't have some of the more fancy features, such as white-balance bracketing or dynamic range optimization, that you'll find on more expensive cameras, such as the Canon Rebel XT or the Sony Alpha DSLR-A100, but for its price, the K-100D is a steal. If you already own Pentax lenses, this camera is a no-brainer. On the other hand, if you're really looking to save money, and shake reduction doesn't float your boat (though it probably should), then you can always step down to Pentax's K110D, which is the same camera without the shake-reduction feature.