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.