The APS-C format includes the smallest current DSLRs, thanks in large part to image sensors less than half the size of full-frame (36x24mm) sensors. The resulting 1.5X "crop factor" (1.6X for Canon) is good for long-lens users like wildlife photographers, and less so for wide-angle landscape fans, as any focal length used on an APS-C camera frames like a lens 1.5X or 1.6X the focal length on a full-frame camera. However, between the camera manufacturers and independent lens makers such as Sigma, Tamron and Tokina, very wide-angle lenses designed specifically for the format are available for APS-C DSLRs, so landscapes don't present the problems they did in the early days of the DSLR, when there were few full-frame DSLRs and no APS-C lenses.
Canon's new 18.0-megapixel EOS Rebel SL1 is the smallest DSLR as of this writing (late April 2013), measuring just 4.6x3.6x2.7 inches and weighing a mere 13.1 ounces. But it features a 3.0-inch, 1040K-dot touch-screen LCD monitor and takes the full range of Canon EF (full-frame) and EF-S (APS-C) lenses. These range from an 8-15mm fisheye zoom and a 10-22mm superwide zoom to an 800mm supertelephoto, providing 35mm-camera-equivalent focal lengths of 16-1280mm (12mm, including the fisheye zoom). These, plus four TS-E tilt-shift lenses and true macro lenses, can handle pretty much any outdoor shooting need. The Rebel SL1 can shoot full-resolution images at 4 fps, provides a normal ISO range of 100-12,800 and in-camera HDR, and stores images on SD/SDHC/SDXC media (UHS-I included). It also can shoot 1920x1080 full HD video at 30p and 24p or 1280x720 HD at 60p, with Movie Servo contrast-based AF during shooting. Canon also offers other larger, but still very compact EOS Rebel models, the top one being the T5i. It has the SL1's features, but the LCD monitor tilts and rotates, normal ISO range is 100-12,800, it can shoot at 5 fps, and all nine AF points are cross-types. The T5i measures 5.2x3.9x3.1 inches and weighs 18.5 ounces.
Nikon offers several compact DSLRs, the smallest (by a small margin) being the 14.2-megapixel D3100 entry-level camera. Landscape shooters will likely prefer the marginally larger 24.2-megapixel D3200 or 24.1-megapixel D5200, which deliver noticeably better image quality, especially for larger print sizes. (The D3100 scored 67 in DxOMark.com's raw sensor ratings, compared to 81 for the D3200 and 84 for the D5200. The D3100 measures 4.9x3.8x2.9 inches and weighs 16 ounces; the D3200, 5.0x3.8x3.1 inches and 16 ounces; and the D5200, 5.1x3.9x3.1 inches and 17.8 ounces. All feature pentamirror viewfinders that show 95% of the actual image area and 3.0-inch LCD monitors (230K dot for the D3100, 921K dot for the D3200 and D5200, plus the D5200's monitor tilts and rotates). The D5200 has better AF and metering systems (39-point AF and 2016-pixel metering vs. 11-point AF and 420-pixel metering), and can shoot faster (5 fps vs. 4 fps for the D3200 and 3 fps for the D3100). The D5200 also offers in-camera HDR. All can accept a wide range of AF Nikkor lenses, but none has an in-body AF motor, so they will autofocus only with lenses that have one: AF-S. AF-S lenses range from a 10-22mm superwide zoom to an 800mm supertelephoto, though equivalent to 15mm through 1200mm on a full-frame DSLR, so all three cameras can handle pretty much any outdoor shooting situation. Normal ISO range is 100-3200 for the D3100 and 100-6400 for the others. All can shoot 1920x1080p full HD video at 24 fps; the D3200 also can do it at 30p and the D5200 at 30p and 60i.
Some of the mirrorless interchangeable-lens cameras have a "flat" form factor like typical compact point-and-shoot digital cameras (albeit with more advanced capabilities), while others look like mini-DSLRs. While some of the former will accept optional clip-on eye-level electronic viewfinders, the latter have eye-level EVFs built in, and can be held and used much like regular DSLRs. This provides a more familiar feel for photographers used to DSLRs (or coming from film SLRs), and provides steadier handholding than the arm's-length hold required when using the external LCD monitor to compose and shoot. (All of the "mini-DSLR"-style mirrorless models have external LCD monitors, too, some with tilting/rotating capabilities.) Of course, the "mini-DSLR"-style cameras are less pocketable than the "flat" ones. Current "mini-DSLR"-style mirrorless models include the Olympus OM-D E-M5, Panasonic Lumix DMC-GH3 and G6, and Samsung NX20.