Point-and-shoot digital cameras have swept the industry with astonishing speed. Today virtually all cameras on the market are digital. The most obvious advantage lies in the end result: digital photos are more versatile and easier to manage in today's digital age. New technology, including DSLR, (digital single lens reflex cameras) is further revolutionizing the picture-taking process. Buy.com's digital camera buying guide will help buyers navigate a potentially confusing array of features and options to make the best purchase decision for their needs.

The key difference between a film camera and a digital camera is the digital camera's ability to display images on a screen immediately after they are recorded since it uses a memory card to store images instead of film. It's still serves the basic purpose of a film camera, but the features you need to consider are different than film cameras. The following outlines these features in more detail:

The two big advantages of point-and-shoot cameras are size and ease-of-use: they're compact and can fit right into your pocket, and they're also quick, easy, simple to use. The disadvantages are you're limited on your lens and you're limited on what the camera can do. But don't be fooled into thinking point-and-shoot cameras are just for beginners. The minimum optical zoom 3x, but many models go as high as 20x magnification. Other available features include movie mode (some with audio), special image effects, and many other options to suit novice and experienced photographers alike. Point-and-shoot cameras are generally also cheaper than DSLRs.

These can also be easy to use, but DSLR cameras give you the ability to change the lens and all of the settings. They also take a much better picture because the imaging chip on a DSLR is larger than a point-and-shoot: about the size of a standard postage stamp vs. the fingernail on your pinkie finger. It's only a few millimeters, but it makes for a big difference in the picture quality and the amount of image you can capture. Unlike point-and-shoots, the zoom ability of DSLRs is measured by focal length.

Optical zoom is a parameter indicating the ability of the lens to make subjects appear closer or further away from the camera. But with DSLRs this parameter is nowhere to be seen. That because SLRs are measured by focal length e.g, 50-200mm. But you can still determine the optical zoom through a simple calculation by dividing these two numbers i.e. 200/50 = 4x. DSLR focal lengths range from 10mm to 600mm or more. As you can see, the higher the focal length, the more magnification. The photos below were taken from the exact same location, using lens with different focal lengths. You can see how the cameras angle of view decreases with an increase in focal length, resulting in the main subject being "zoomed in".

A full-frame body has an image sensor that is the same size as a 35mm film frame. That's because 35mm was been the standard film size for DSLR's for many years, so it was used as a reference. But for various reasons, including cost, the majority of digital sensors are made in a smaller size. That means when you attach a lens, the 'field-of-view' is magnified by a 'factor' - On Canon cameras this factor either 1.3x or 1.6x depending on the model. On Nikon cameras it's 1.5x. So any lens fitted to a crop body is 'seeing' more than the view you will see in your viewfinder, as the sensor is only going to 'see' the centre part of the projected image. This is the same as 'cropping' the image from a 35mm image, or in effect 'blowing it up' by a factor of 1.6x, thus giving a narrower field of view on the final image.

(insert image with various crop factors outlined on it-full frame, 1.3x, 1.5x, and 1.6x)

In an image sensor, more pixels mean better light-gathering capability. But pixel size is also a factor, and as manufacturers put more pixels on their sensors, the pixels get smaller and smaller. So how many megapixels do you need? For A casual user 12MP is likely more than enough. And with a good lens 6-8MP might well suffice. Keep in mind that more megapixels means a bigger file size. So shooting hundreds or even thousands of 12MP images means larger memory cards, more space eaten up on hard drives, and more time sorting and editing-all for images that may end up viewed at no larger than 800 x 600px... or about half a megapixel. That said, keen enthusiasts and professional have more demanding needs, in which case image sensors of up to 20MP or more are available.

Point-and-shoot models are limited to one lens with either a fixed focal length or zoom capability. DSLR cameras have a wide assortment of flashes and filters, and can be fitted with many high quality lenses ranging from wide angle to super long focal length. Of course, that also means more gadgets to lug around with you. Lens choices are generally grouped as follows:

10-35 mm: Wide, Ultra Wide and Fisheye lens - large angle of view suitable for architecture and landscape

35-70 mm: Normal lens, within the range of the human eye (50mm) - suitable for street shots and simple indoor photography

75-135mm: Medium telephoto lens, 1.5-2.5 magnification - suitable for portraits and blurring backgrounds

135-600mm and over: Telephoto lens, 2,5x to 10x and more magnification - suitable for wildlife photography and sports

DSLRs are designed for manual use. This maximizes the creative choices offered to today's photographer. The array of settings and features can be a bit overwhelming at first, but once mastered you'll be pretty quick on the draw. DSLR cameras also have a fully automatic mode, and many have the normal array of semi-auto modes that point-and-shoot digital cameras have. That said, they're called point-and-shoot cameras for a reason. Some entry-level Nikon models have a real-time user guide that will prompt you to try different settings. Features like Face Detection are also proving hugely popular. This technology lets you detect faces in a scene, automatically focus, and optimize the exposure (including flash if needed). Other features include Smile Detection, which prevents the camera from snapping a photo until the subject smiles; Blink Detection, which only allows the photo to snap when the subject's eyes are open; Blemish Removal, which takes out pimples and birthmarks, and Digital Slimming, which narrows the image to give the illusion of weight loss. Samsung's new "Smile Correction" can even turn up the corners of a subject's mouth, and adjust other facial expressions too.

Portability is a wonderful thing, and not just for convenience. Entry-level point-and-shoot cameras are slim and light - some to the point of not even feeling them in your pocket. But light pro-level DSLRs can also be found, with the latest Nikon D40x camera weighing in at just over a pound. One choice to consider is body construction. Camera bodies made of plastic polymers are lighter (and cheaper) than magnesium bodied cameras. However, a magnesium body will likely prove more durable in the long run.

ISO ratings pre-date digital cameras (it measured film speed) but they're still the industry norm. Point-and-shoot cameras come with a pre-set ISO, but a DSLR let's you override the auto-setting to select an optimal ISO, which improves your flexibility for shooting in different conditions. A 200 ISO is considered good for general shooting, whereas an ISO of 800 will produce shots with a grainy look and feel. Some cameras can also auto-correct the ISO setting to accommodate a dimly lit environment.

Many point-and-shoots come equipped with a limited manual mode, but it's not part of the camera's DNA. DSLR cameras are designed to give you maximum control of the settings. While they do come with good auto modes, the manual controls are generally positioned to be fingertip-ready for shooting. Here's three key manual controls to familiarize yourself with:

AV Setting: The aperture priority or AV mode (A mode on Nikon) determines whether all of your photograph is in focus, or only part of. This lets choose to have a sharp foreground and a blurred background, for instance.

TV Setting: The TV (time value) setting can also be adjusted to freeze or blur the action in a shot-very useful for shooting sports and wildlife.

B Setting: This controls the time the shutter of the camera is open, which means the same as the time that the film is being exposed. Usually the B setting works by pressing the release button which opens the camera shutter, and releasing the button which closes the shutter again. In the meantime, while you keep the button depressed, the shutter stays open and the film is being exposed. This allows you to make exposures for several seconds, minutes, or hours. The B setting is necessary for shooting things like lightning, the stars or the aurora borealis.

With DSLR, the lens choices are married to the brand of camera you choose, yet the choices are still endless. Two things, both controlled by the lens, can increase your creative input in the shooting process. One is the aperture, or lens opening (which changes in size), and the other is the speed at which the light enters the camera (Shutter speed). It is a combination of these two things that determines proper exposure on your photos. With the DSLR, your choices are either fully manual, fully programmable, or easy select icons like action, macro, portrait or wide angle. DSLR cameras also have full manual and semi-manual priority settings. This is where you get to control the creative end of the photograph and push the limits of the standard automatic choices.

A faster shutter speed will reduce the amount of motion the camera's image sensor will capture. So, if you plan to take a lot of animated shots (sports for instance) you'll need a high shutter speed. 1/125 is fine to capture kids playing hockey, whereas a golf swing might need a faster shutter speed (1/500 to 1/200). General rule of thumb is: don't use a shutter speed slower than the reciprocal of the length of your lens. For example, if you are using a 200x lens, then the slowest shutter speed you should use (without a tripod) is 1/200 or the next closest which is 1/250. Note that a tripod is still a good idea in many situations (strong breeze, unsure footing, or when using a heavy lens that's hard to hold steady. However, a tripod can't be used if you are standing in fast-flowing water, are in scrubby woodland, or on very steep ground. In that case you may be able to use either a monopod or beanbag for more stability.

Be aware though, that fast shutter speeds mean less light gets through to the sensor, which makes it challenging to shoot in dimmer environments where there's less original source light. There are ways to adjust the camera in these situations. One is to allow more light to pass through the aperture. This is accomplished by adjusting the f-stop settings. All lenses are marked with a series of f-stops, each one allowing half as much light as the previous one. The f-stop number is simply the focal length divided by the diameter of the lens. For example, a 200mm f/4 lens will be 50mm wide.

Some lenses for DSLR cameras are now available with Image Stabilization (IS). This allows you to break the "rule of thumb" and shoot a slower shutter speeds. Note however, that most DSLR lenses are brand-specific, and even within a given brand not all lenses are compatible with all cameras.

DSLR lenses are larger, and more glass generally means higher quality. They're also manufactured separately from the camera itself, which usually means higher standards and greater attention to detail. Many are threaded to accommodate converters or filters. Lens quality really does make a huge difference in photo quality.

With a point-and-shoot camera, the computer within the camera is going to make all of your shutter speed and aperture setting choices for you. It has a multitude of possible exposures, all offered up a selection of icons and menus. This includes back lighting, candlelight, action, portrait, and etc. This only appears limiting to the enthusiast who wants to explore more choice. For the point-and-shoot user, the process is super-simple and delivers great results.

Although the lenses are generally not interchangeable, there are different types of lenses available to the consumer. A standard 3x fixed focal length lens point-and-shoot camera provides a relatively wide viewing angle, which is perfect for group shots of family and friends, and vacation shots of landscapes. Zoom models are also available, which will expand your focal length options substantially. Another point-and-shoot lens option is retractable zoom, offering the ultimate in convenience.

Point-and-shoot digital cameras are generally cheaper, though top end models certainly overlap with lower end DSLRs. Note too; the latter are coming down in price as various features migrate from "special" to "standard" status. That said, the number of potential add-ons for DSLRs is far greater. And while extra lenses, flashes and filters will increase your shooting options, it will also increase your cost.

Every time you change lenses on your DSLR camera you run the risk of getting dust on your lens or image sensor, which will leave your images looking blotchy. Cleaning your image sensor can tricky, and better done by a professional. Note: some newer DLSR models have a self cleaning sensor.

Sometimes editorial inspiration strikes right after the shot is taken. In-camera editing lets you resize, copy, or make other changes to your images before you download them to a computer. In-camera editing features can include: red-eye correction, image trimming, image overlay, monochrome black and white, sepia and cyanotype along with skylight, or warm tone and custom color filter effects. The net result is greater creative freedom and the ability to send pictures directly to a printer without intermediary computer editing .

Special Image Modes

Cameras with special shooting modes let you capture stop-motion animation, 3D pictures, and other special types of images.

Not content with still shots? Some digital cameras have a video clip capture feature. It's not camcorder quality, but 1080p HD is now available. Check for HDMI outputs to connect directly to your HDTV. Sound capture, zoom-while-filming, and in-camera editing is offered on higher-end models.

Most digital cameras come equipped with an internal memory or low-capacity memory card, but you'll likely want more. It helps to understand the relationship between file size and image resolution. An image's actual size (the amount of memory it will consume) is the number of pixels in the image multiplied by the bit depth. So a 3-megapixel photo with dimensions of 2,048x1,536 has 3,145,728 pixels; if it's a 24-bit photo, that means each pixel needs 24 bits of data to describe it, or 75,497,472 bits. Converting the units means it will take up 9MB of memory.

Flash-memory cards are the most common type of storage media, of which SDHC cards are currently the most popular. Capacity varies depending on the card type, your camera's compression capabilities, and the settings you choose when saving photos. Higher compression equals more pictures, but may result in lower quality images. Consider card compatibility if you own other digital devices like an MP3 player or PDA. Also, different manufacturers support different storage mediums, so check compatibility there too. Here's a quick breakdown of storage media formats and storage capacity.

CompactFlash: fast, large capacity, inexpensive…larger in size than other media types.

Secure Digital High Capacity (SDHC): fast, large capacity, wide compatibility, inexpensive, smaller size

Xd Picture Card: smallest format but less capacity (Olympus brand only)

Memory Stick: smaller format but may require adapter (Sony brand only)

Many digital cameras will only accommodate manufacturer-specific or camera-specific rechargeable batteries- usually lithium-ion. These allow for a more compact camera design, and are generally more accurate at displaying your remaining battery life. Disposable batteries are still a convenient option for many situations, but they're more expensive over the long run, and less environmentally friendly.

Two LCD Screens

New from Samsung is a camera with one LCD screen in front, and one in back. It's a great solution for self portraits, allowing you to set the timer, take your position, and check your appearance. You can also use the front screen to play animated clips to get the attention of children while snapping their picture.

Wireless

Yes, wireless technology has come to digital cameras too. A wireless-enabled camera lets you send images to a compatible device, or upload images to a photo-sharing service. Some professional SLRs are compatible with wireless transmitters that you attach to the camera.

Videoconferencing

If you use your camera for business this feature is perfect: It let's you video-conference anytime, anywhere-just like a webcam. Videoconferencing software is included with the camera, and it will usually have a built-in microphone (check to make sure). Some models even have a USB cradle to stand your phone on while conferencing.

Waterproof

You needn't be an underwater photographer to appreciate the benefits of this feature. A waterproof camera lets you take photos in the middle of a rainstorm or your bathtub. Underwater housings are also available to adapt your digital camera to this purpose.

In conclusion, manufacturers have designed digital cameras that can fill needs from the basic to the complex, and everything in between. Once you determine which features are most important to you and fit within your budget, there is a vast selection of cameras to choose from.