A still camera that records images in digital form. Unlike traditional film cameras that record a light image on film (analog), digital cameras record discrete numbers for storage on a flash memory card or optical disc. As with all digital devices, there is a fixed, maximum resolution and number of colors that can be represented. Images are transferred to the computer with a USB cable, a memory card or wireless. Digital video cameras (see camcorder) also use FireWire.|
There are three distinct advantages of digital cameras over their analog counterparts. First, you can review the finished image immediately and erase the others. Second, you can take and print one picture without waiting to develop an entire roll of film. Finally, memory cards, the storage mechanism most widely used for "digital film," are reusable over and over.
Chips: The Camera's Film
Digital cameras record color images as intensities of red, green and blue, which are stored as variable (analog) charges on a CCD or CMOS image sensor chip. The charges are converted to digital and stored in flash memory chips on a memory card such as CompactFlash, SD or Memory Stick. Some still cameras use optical discs for storage instead of flash memory, and video cameras use tape, optical discs and hard disks (see DV).
The size of the CCD or CMOS chip determines the picture's resolution, but the analog-to-digital converter (ADC), which converts the charges to digital data, determines the color depth. In 2002, Foveon introduced a breakthrough in color accuracy with its X3 CMOS chip (see Bayer pattern and X3).
Digital video cameras use the same image sensing methods as still cameras, but in addition to storing the images digitally, they output NTSC video for playback on any TV. See flash memory, photo editor, photo scanner, X3, digital camera record modes and DSLR.
Following are the major features and some caveats of digital cameras.
Resolution in Megapixels
The number of pixels determines the maximum size of the resulting image and its sharpness, especially when printed. The higher the resolution to start, the better the results. You can easily reduce a high-resolution image to low resolution in the computer, but you cannot go from low to high with great results. The bottom line: know the final destination of your images. Following is a guide to the amount of megapixels required in the camera:
Destination Minimum Megapixels
Web site images 1 MP
Computer screen 2 MP
3x5 and 4x6 prints 2 MP
8x10 print 4 MP
11x14 print 6 MP
16x20 print 12 MP
Nothing is more critical to photographers than the feel of their cameras. Because it uses a combination of physical buttons and on-screen menus, a digital camera's interface can be more daunting than that of a desktop computer. At the very least, spend some time in the store reviewing the basics. If at all possible, borrow the camera from a friend for a photo session.
Optical and Electronics Quality
As it has in film cameras for nearly two centuries, the optical quality of the camera's lens greatly contributes to the resulting picture quality. In addition, the color and geometric accuracy of the pixels in the CCD or CMOS sensor combined with the camera's internal processing circuits can make all the difference. Specifications on paper are not enough, and reviews from sources such as photographic Web sites are very informative.
Optical vs. Digital (Interpolated) Zoom
The optical zoom is the real resolution of the lenses. The digital zoom is an interpolated resolution computed by software. The higher the optical number, the better. A 10x optical is far superior to a 10x digital (see optical zoom).
There are several types of flash memory cards used for "digital film," but no matter which type the camera uses, the one that comes with the camera is typically undersized. Plan on purchasing a larger one when you buy the camera (see flash memory).
Digital cameras come with a USB cable for transfer directly to the computer, and many computers come with one or more memory card slots. Printers may also come with card slots, allowing you to print your photos without using the computer at all. Wireless (Wi-Fi) transmission is also available on some cameras.
Digital cameras use either rechargeable or standard AA batteries. It can take an hour or more to recharge a battery, so having an extra, fully charged battery is recommended. AA batteries can be purchased anywhere, and rechargeable AA's can also be used.
Digital SLR (single lens reflex) cameras are the digital counterparts of their analog predecessors and may use the same removable lenses that you already own. However, the sensor chip may be smaller in size than a 35mm frame, which means your 28mm wide angle lens might function like a 42mm lens. Lenses made specifically for the digital SLR do not have this focal length mismatch. See DSLR.
LCD Screen and Viewfinder
Small, point-and-shoot cameras use a "live preview" LCD screen to take pictures and display the stored images. Digital SLRs have a traditional viewfinder that you press your eye against for taking pictures and mostly use the LCD as a monitor to show the results. The larger the LCD screen, the more the camera serves as a convenient playback device.
The eyepiece viewfinder has always been an effective method for taking pictures because pressing the camera against the eye actually steadies it. It also helps the photographer frame the picture by eliminating everything outside the viewing area. In addition, the LCD can sometimes be so washed out in a bright sunny day that it becomes difficult to take a picture. As a result, some point-and-shoot cameras also include a viewfinder. See viewfinder.
Behind the lens, a CCD or CMOS image sensor chip picks up the image as variable (analog) charges that are turned into digital by an analog-to-digital circuit (see
A classic now, the DC50 was one of the first digital cameras from the venerable Kodak company. Holding 24 images in internal memory, it used flash disks for more storage. (Image courtesy of SanDisk Corporation, www.sandisk.com)
FARGO made one of the first printers designed for 4x6" photographic prints. The 1995 introduction of the $595 FARGO FotoFUN! was a breakthrough price for a dye sublimation printer. (Image courtesy of FARGO Electronics, Inc.)
CYCOLOR printers are different than other digital printers, because the imaging is done inside the paper, which is sensitive to light (see
Photo printing companies such as Photoworks and Kodak EasyShare Gallery (formerly Ofoto) let you upload your digital pictures to their Web sites so they can be previewed by family and friends from any Internet connection. Clicking on a thumbnail (top) displays a larger, low-res image (bottom). High-resolution prints can be ordered by anyone. Undeveloped analog film can also be sent to the companies for processing. (Images courtesy of Jim and Karen Clayton.)