The smallest Pentax DSLR is the K-30, at 5.1x3.8x2.8 inches and 20.8 ounces. The higher-end K-5 II and K-5 IIs models (the latter with no anti-aliasing filter over the sensor and thus capable of the greatest resolution) are marginally larger at 5.2x3.8x2.9 inches and 23.3 ounces. All feature excellent 16.3-megapixel image sensors (the 12-bit K-30 scoring 79 at DxOMark.com, the 14-bit K-5 models, 82), and all feature rugged weatherproof/coldproof bodies. Current lenses range from a 14mm superwide to a 560mm supertele (equivalent to 21mm through 840mm on a full-frame DSLR), including macro lenses. (DA* and WR lenses are weatherproof, like the camera bodies.) Pentax DSLRs also can use all K-mount Pentax lenses and, via adapters, even medium-format and old screw-mount Pentax lenses. Other features of note to outdoor photographers include in-camera HDR, pentaprism finders that show 100% of the actual image area, 3.0-inch, 921K-dot LCD monitors (with live-view focus peaking) and quick shooting (6 fps for the K-30, 7 fps for the K-5 models). You also can shoot 1920x1080 full HD video at 30 fps or 1280x720 HD at 60p.
Sigma's smallest DSLR is the SD15 at 5.7x4.2x3.2 inches and 24 ounces, but the much newer SD1 Merrill measures only marginally larger at 5.7x4.4x3.1 inches and 24.7 ounces, yet provides 3X the pixel count, much better image quality and better weather resistance, and is an all-around better choice for outdoor photography, landscapes and wildlife. The key feature of the SD1, of course, is the unique Foveon image sensor, which records all three primary colors at every pixel site. Conventional sensors used in other DSLRs record only one primary color at each pixel site, producing the missing colors by interpolation via complex proprietary algorithms via a process known as demosaicing. This process produces moiré and artifacts, which are dealt with by using an anti-aliasing filter over the sensor. This slightly blurs the image at the pixel level, reducing sharpness. The Foveon sensor requires no demosaicing, and thus no anti-aliasing blurring filter, so image detail is much better than with a conventional sensor of equivalent horizontal-by-vertical pixel count.
Sony's smallest current DSLR is the 20.1-megapixel Alpha SLT-A58, at 5.2x3.8x3.1 inches and 17.3 ounces. Like all Sony SLT models, it features the company's TMT (Translucent Mirror Technology), with a nonmoving, semitranslucent mirror that transmits most of the light to the image sensor, while simultaneously sending a portion to the phase-detection AF sensor. Thus, you get full-time phase-detection AF, even for video shooting, and there's no mirror vibration to blur long-exposure landscapes. An eye-level OLED electronic viewfinder replaces the conventional DSLR's optical finder, so you can shoot video with the camera at your eye—much more convenient and stable than holding it at arm's length and using the rear LCD monitor (that tilts, for convenient high- and low-angle shooting). Of special interest to outdoor shooters are in-camera HDR, easy Sweep Panorama, Multi-shot NR, Handheld Twilight mode and SteadyShot INSIDE sensor-shift image stabilization that works with all lenses. Sony A-mount lenses range from an 11-18mm superwide zoom to a 500mm supertelephoto, providing focal lengths equivalent to 16.5-750mm on a full-frame camera. (Sony DSLRs also can use legacy Konica Minolta lenses.) Normal ISO range is 100-16,000. The A58 can shoot 1820x1080 full HD video at 60i and 24p. If you want more pixels for big landscape prints or faster shooting (10 fps with continuous AF vs. 5 fps for the A58), the 24.3-megapixel SLT-A65 is only a bit bigger at 5.2x3.8x3.2 inches and 19.1 ounces, and also offers a larger 3.0-inch, 921K-dot monitor that rotates, as well as tilts.
Four Thirds System DSLR
Olympus' pro-oriented E-5 is the only current Four Thirds System DSLR, and thus the most compact. It's actually about the same size as the compact full-frame DSLRs described in this article, but the smaller 17.3x13.0mm Four Thirds image sensor means lenses can be much smaller for a given field of view: A 300mm lens on the E-5 frames like a 600mm on a full-frame DSLR, but is much smaller than a 600mm. The 12.3-megapixel E-5 features a rugged splash- and dustproof body, a tilting/swiveling 3.0-inch, 920K-dot LCD monitor, a normal ISO range of 100-6400 and 5 fps shooting. It also can shoot 1280x720 HD and 640x480 SD video at 30p. Current lenses range from a 7-14mm superwide zoom (equivalent to 14-28mm on a full-frame DSLR) and an 8mm fisheye to the aforementioned 300mm (600mm equivalent) supertelephoto, plus 1.4X and 2.0X teleconverters.