The resolution of an image sensor tells you how many discrete points of light, called pixels, it can capture. The higher the number, the more you can enlarge the image without significant quality loss. More is not necessarily better, since resolution is only one factor affecting overall image quality. Consider optical resolution only, which is the physical resolution - the actual number of image-sensing elements.
The most common kind of image sensor for digital cameras is the Charge-Coupled Device (CCD). CCDs usually produce higher-quality images than devices based on CMOS, the other common image-sensor technology. CCDs are more difficult to manufacture, require additional circuitry, and generally use more battery power.
Image sensors produced with the Complementary Metal-Oxide Semiconductor (CMOS) technology require less circuitry than CCDs, but the image quality is usually not as good. This means that these cameras can be made very small and are usually found in low-cost, limited feature digital cameras.
This measures the amount of light a digital camera needs for a perfectly exposed picture. This is stated as ISO equivalency (expressed in the same terms as film photography). A low ISO setting (50 - 100) usually produces better, cleaner images but the pictures can be dark if not shot in bright sunlight or using a flash. Higher ISO settings (200 - 1,600) can produce better-exposed pictures in low light, but also introduce more electronic noise, which can degrade image quality.
IMAGE CONTROLS
White balance
If whites look correct in your images, the rest of the colors in your photo should appear closer to actual colors of the scene. This is known as white balance. All digital cameras can automatically adjust the color of your picture so that white always looks white, regardless of the light source. Better cameras give you the option to set white balance manually or choose a preset light source.
Program mode
The program mode prepares your camera to take special photographs automatically by using preset commands. Settings include night scenes, sports and action subjects, portraits, sepia, black & white, and other shooting conditions.
Image enhancements
These settings allow you to intensify or tone down aspects of your photo. You can boost or reduce contrast, brightness, color saturation, and sharpness. Some cameras allow you to add fireworks or borders.
Image enhancements
These settings allow you to intensify or tone down aspects of your photo. You can boost or reduce contrast, brightness, color saturation, and sharpness. Some cameras allow you to add fireworks or borders.
Panorama
This feature allows you to shoot a sequence of images, each from a slightly different position and then attach them together into a single photograph. Some cameras with this feature will display the overlapping guides for each image in your LCD viewfinder before you shoot which gives you better panorama results. Other cameras simply provide software to perform this function. Some cameras with panorama mode simply creates one ultra-wide shot.
LENSES
Lens Speed
Lens 'speed' actually refers to the amount of light the lens lets in when its light-restricting diaphragm is completely open. The unit of measurement is the f number or f-stop (the same unit used to describe the size of a lens diaphragm's aperture). A fast lens of f2 or f2.8 is suitable for shooting in low light but limits the depth of field, throwing the foreground and background out of focus. Many digital cameras feature mechanical diaphragms that can stop down (reduce) the aperture to anywhere from f8 to f11 for producing greater depth of field.
Focal Length
This is the distance between the lens and the image sensor. When the lens is modified to increase the focal length, objects appear magnified and closer. Decreasing the focal length makes things appear further away but this also widens the field of view for the image. Most digital cameras have small lenses with tiny focal lengths. Since the image-sensor area is smaller than a film frame, you can't compare the lens focal length of a digital camera with that of a film camera. So, most digital camera makers also post the equivalent 35 mm focal length.
Zoom
The zoom provides the ability to vary the focal length of a lens between wide angle and telephoto, usually by pressing a button or turning a ring on the lens. This gives you wide angle to telephoto coverage in a single lens. The zoom ratio is usually expressed as a number followed by X, which stands for the number of times the focal length is doubled. Digital Zoom is a software method of spreading the pixels farther apart to make the image fill up the picture frame but optical zoom is the physical focal length of the lens. Optical zoom is what produces excellent image quality, digital zoom can actually degrade image quality.
Macro
This is a function that allows a lens to get very close to the subject, usually to take pictures of small items. In this mode, the lens can capture an object 12" away or closer - some cameras are able to get as close as ½". Most digital cameras include a macro mode that extends the normal focal range of the camera.
Auxiliary Lens
This is an optional wide-angle or telephoto lens that screws in or otherwise attaches directly in front of the primary lens. This type of lens will add bulk and weight to a camera, can only be used with the LCD viewfinder not the eye-level viewfinder), and reduces light reaching the image sensor by from one to two f-stops.
EXPOSURE CONTROLS
Auto-exposure
The auto-exposure setting is the default for most digital cameras. This setting allows the camera to have total exposure control without requiring you to set anything. A sensor on the camera measures the light reflected from a scene or subject and automatically sets the optimum combination of f-stop (aperture) number and shutter speed.
Exposure value compensation
Identified as EV, exposure compensation lets you adjust overall brightness or darkness in precise increments. Bump up the exposure compensation toward the plus side for brighter pictures. High-end digital cameras have 2 to 3 f-stop EV settings in both directions, in 1/3 f-stop increments. Less expensive cameras have 1 to 2 f-stop EV in both directions, in only ½ f-stop increments.
Shutter priority
This feature allows you to set the shutter speed and automatically maintain perfect exposure. Increase the shutter speed to capture action shots and the camera will automatically reduce the f-stop setting.
Aperture priority
This feature allows you to set the f-stop number and automatically maintain perfect exposure. A higher f-stop number, which sets the aperture to a smaller lens opening, will increase your depth of field. A lower f-stop number will cause your background and foreground to have a soft focus. The camera will automatically change the shutter speed when you change the aperture, allowing the right amounts of light to hit the image sensor needed to take the photograph.
Manual exposure controls
This is designed for advanced photographers and enables the shutter speed and f-stop to be adjusted independently of each other. Burst mode
Many digital cameras have the ability to take a series of pictures in a very short amount of time. This is great when shooting moving objects and provides a motor drive-like sequence to capture every frame. The flash will not operate in burst mode and it takes longer to save these images, increasing the wait time before the camera is ready to shoot again.
Auto bracketing
This command sets the camera to capture a series of photos of the same scene or subject, with each shot set at a slightly different exposure setting. Most auto-bracket for 3 frames but some allow 5-frame bracketing. Most cameras auto bracket by varying f-stops, but some high-end models let you choose auto bracketing by f-stop or shutter speed. A few digital cameras allow auto bracketing by white balance and exposure.
Best shot selector
This feature captures 4 to 9 shots almost instantaneously. Each frame has a slightly different exposure or white balance setting. This is similar to auto bracketing except you get to choose which images you want to save and the others are discarded automatically. Some best shot selectors allow the camera's intelligence to select the best exposed and sharpest images automatically.
Some Common Terms:
Batteries
Digital cameras often use up battery power in a matter of minutes. To avoid the expense and inconvenience of replacing the batteries, select a model with rechargeable batteries or buy rechargeable batteries and a recharger. For extra power, invest in a second set of rechargeable batteries.
AC Adapter
Most digital cameras do not come with AC adapters, so you should consider buying one. This is a valuable accessory that allows you to shoot from a tripod or remain tethered to a computer for as long as you want. AC adapters draw power from an electrical outlet, saving battery power and ensuring continued shooting.
Aperture
An adjustable iris or opening through which light enters the camera lens. A larger aperture gives the camera greater photosensitivity. A smaller aperture gives greater depth of field to the image. The setting for aperture is called the f-stop. Higher f-stop numbers signify a small aperture (f8 to f11) and a larger aperture has a smaller number (f2.8). Aperture settings must be balanced against shutter speed so that fast shutter speeds must have larger aperture and vice versa, to admit the right amount of light.
Compression
This process reduces the amount of data representing an image so that the file takes up less space in your camera, memory card, and computer. Compressing and saving an image actually takes less time than saving an uncompressed image. Smaller files are quicker to use for E-mail and on the Web.
Depth of Field
This is refers to how much of the scene will be sharp and in focus. A greater depth of field means an increased distance between the well-focused background and foreground with everything in between properly focused. A narrow depth of field has a small range of focus based on the central subject's distance from the camera.
Image Sensor
This sensor is a semiconductor chip that replaces film. It captures the light of a scene or subject and turns it into electrical signals that the camera can understand and use. These signals are converted to digital data that the computer can understand and use. The most common image sensor types are CCD (charge-coupled device) and CMOS (complementary metal-oxide semiconductor).
Interpolation
This is a process that occurs in your camera or your computer software. This process increases the image file size allowing a picture to be magnified. Interpolation does not improve image quality and can decrease sharpness. This is the opposite of compression.
LCD Viewfinder
This is a small electronic screen on the camera that displays what the lens is seeing. This can be used to compose pictures, choose settings, focus and frame an image in macro mode, and view just-shot photos.
Megapixel
A megapixel is a measure of a digital camera's resolution. One megapixel captures up to 1 million pixels, or points of data.
Memory Card
Memory cards are small, removable storage that saves the images. When the card is full, you can swap with another card or download and erase the images from the card to continue shooting. A card reader that is attached to your computer will open and save image files outside of your camera. Memory cards come in many densities. The most common types are CompactFlash, SmartMedia, and Secure Data (SD). You must use the card type that is compatible with your camera.
Pixel
A point of data in a digital image is called a pixel. This is short for picture element. The camera's resolution is measured be the number of pixels it can capture on its image sensor.
Shutter Speed
Expressed as a fraction of a second, the shutter speed of the camera measures how long a camera allows light to fall on the active image sensor. In film cameras, this is a mechanical shutter in the lens that opens and closes to regulate the light exposure. Many digital cameras have both electronic and mechanical shutters.
