Continuous shooting mode: If you take photos of sporting events, kids, or any other fast, unpredictable subject, a continuous-shooting (or burst) mode will make a huge difference in your photography. This mode lets you hold down the shutter button to shoot multiple photos in rapid succession. The number of pictures you can record in one burst is determined by your camera's electronics--and in some cases by the type of memory card you have. You may need a more high-speed memory card to take advantage of your camera's fastest shooting rate. If so, be sure to factor that cost into your decision. To be effective, a continuous shooting mode should capture images at least 3 fps (frames per second) or faster at the camera's highest resolution.
Face Detection: With this mode turned on, your camera locates the people in a shot and then fine-tunes the focus and exposure for those faces. While this may sound like a superficial gimmick, we've found that it works surprisingly well--greatly increasing your chances of getting good shots at a wedding or family reunion. Typically, this option is in the camera's autofocusing (AF) menu. Face detection is particularly handy for candid shots, where you're working quickly and are thus more vulnerable to misfocused shots. It's also a boon for flash photography. With face detection turned on, the flash doesn't try to illuminate the whole room, just the people within range--cutting down on the nuclear blast effect.
Video: Many DLSRs now offer video recording features--often at HD resolution. You'll have to make some usability compromises that you wouldn't have to make if you used a camcorder but the video quality is often worth it. And because you can take advantage of a variety of lenses, including fish-eye lenses, you can achieve interesting video effects with an SLR. Remember that video requires a lot of storage space, so plan accordingly.
Storage: If you have an existing storage card that you'd like to use with your new camera, make sure that it's compatible with your new purchase. Most cameras on the market today use SD (Secure Digital) or SDHC (Secure Digital High Capacity) format cards. SDHC (Secure Digital High Capacity) cards are more expensive, offering storage capacities up to 32GB, but they're not backward-compatible with standard SD slots. There's also a new format on the block: SDXC, which supports storage capacities up to a whopping 2TB; those are even more expensive, and they aren't compatible with all SD/SDHC card slots.
In addition to storage capacity, there's also the speed issue to consider. SD and SDHC cards have a "Decoding Class" rating listed, which refers to the data-writing rate for each card. The higher the Class number, the faster the write speed; if you're planning on shooting video or using a high-speed burst mode, look for a Class 4 or Class 6 card at the very least.
To complicate matters further, there are a couple of other formats out there. Some cameras support MicroSD or MicroSDHC cards, a smaller version of the SD card format that isn't compatible with full-size SD slots. Older Sony cameras take MemoryStick cards, and older Olympus cameras use the XD card format; both companies' new cameras now support SD/SDHC cards. What's more, many higher-end DSLRs have a larger-format CompactFlash card slot. You'll want to consider all of these options when purchasing storage for your camera, though it is definitely easiest to go with standard SD/SDHC cards since you will be able to use them across cameras.
Battery life: Cameras use one or more of several types of batteries: AAs, either non-rechargeable alkaline ($5 for four) or rechargeable nickel metal hydride (NiMH, about $14 for four); high-capacity disposable CRV3s (around $10 apiece, and some cameras take two); or proprietary rechargeable batteries that can cost $25 to $65 to replace. Some digital cameras quickly drain batteries--especially alkaline batteries--which can be expensive and annoying. Battery life and cost often aren't related; some inexpensive cameras have great battery life, and some expensive ones use up a charge quickly. Either way, it's a very good idea to buy spare batteries.
Menus: When evaluating a camera, consider how easily you can reach common settings--resolution, macro mode, flash, and exposure adjustments--and how easily you can play back just-taken images. Too many buttons, and you waste time trying to figure out which button does what; too many menus, and you waste time digging through them.
Compact interchangeable lens cameras: These cameras, sometimes called CILCs, are part of a somewhat new product category that sits between true SLRs and advanced point-and-shoots. The design of these cameras omits an SLR's mirror chamber and moves the sensor closer to the back of the lens. The lack of a mirror chamber allows for a smaller camera body, while moving the sensor closer to the lens allows for smaller lens design.
All of this means that CILCs and lenses can be made much smaller than those from a traditional SLR, while delivering the image quality of an SLR and the flexibility of using additional lenses. However, this also means they lack an optical view finder. Some cameras in this category offer an electronic viewfinder instead; others--particularly those at the smaller end of the scale--lack even that and rely completely on the LCD for framing shots.
With all of the above factors to consider, its impossible to recommend the best cameras for everyone. Much depends on budget, size, shooting style, and personal preferences. Here are some places to start:
Sub $1000 full DSLRs: Pentax K-x, $650; Canon T3i, $900; Nikon D3100, $700; Canon EOS 60D, $1000 (For more, check out our chart of the best DSLRs under $1000.)
Above $1000 full DSLRs: Nikon D7000, $1500; Pentax K-5, $1750; Canon EOS 7D, $1700; Olympus E-5, $1700; Sony Alph SLT-A77, $2000; Canon EOS 5D Mark II, $2700
Translucent mirror DSLR: Sony a55, $750; Panasonic Lumix DMC-GH2, $1000
Compact interchangeable lens camera: Sony NEX-C3, $600; Samsung NX100, $600 (For more, check out our chart of the top-rated interchangeable lens cameras.)
This story, "DSLR camera buying guide" was originally published by Macworld.