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Terminology - How Digital Cameras Work

There are a few key things you need to understand to make sense of digital cameras. Due to the nature of how they capture and handle light differently than film cameras, there are some new terms to learn and master. Some of them are:

Sensors/Pixels
Digital cameras capture light (electrons) with sensors composed of pixels. There several different types of sensors out there, most commonly CCD and CMOS designs. The sensors themselves are composed of pixels (short for "picture element"), which are what actually capture the light. Pixels are normally counted by the million, thus a two-megapixel camera will have about two million pixels, where a five-megapixel camera will have about five million. Larger pixels generally give a higher quality signal (lower noise ratio) than small pixels, which is why you can have more expensive cameras with smaller total pixel counts producing higher quality images than compact cameras with more pixels.

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Image Processing
Digital cameras don't just capture light and write that information to a media card. After capture, the light is then converted into a digital signal, and now one of two things happens: either that information is written to the card in a Raw format, or the image is processed for color, tone, noise, sharpening, etc., and then saved as either a TIFF or JPEG to the card. If the image is saved as a Raw file, then that processing will have to happen outside the camera, in the computer through the use of special software (either the camera manufacturer's or a third party application). This processing, whether done in camera or outside, is critically important in determining final image quality. This is where different camera manufacturer's can vary widely in what they interpret proper color and other variables to be. Lastly, it's important to note that it's not just the capture and processing of the information that's important. Without a high-quality lens, metering system, and good autofocus not even the best post-processing can create a high-quality image. As with most things in life, in digital photography, you get what you pay for.

File Formats
One of the choices you'll make when first setting up your camera will be to choose a file format to save the images in. Almost all digital cameras give the options of JPEG or TIFF. Some compact cameras and most digital SLR's also allow images to be saved in Raw format. To understand the different formats, it's important to remember the path the image takes inside the camera.

• Raw
When the electrons captured by the pixels are converted to a digital signal, you have a Raw file. A Raw file will need to be processed in-camera or with special software to reveal a full-color, full-quality image. The size of the Raw file will be somewhere between that of a TIFF and a JPEG file.

• TIFF
If that Raw file is processed in-camera to create an image file, you have a TIFF (Tagged Image File Format) file, that can be opened by any image editing software. TIFF is an international standard format for photos. It will be large, though. A two-megapixel camera will create about a 5.5-megabye file. A six-megapixel camera will create about a 17-megabyte file. Obviously, you'd need very large media cards to save files of that size.

• JPEG
This (Joint Photographic Experts Group) format is an international standard for compression of photographic images. It works by looking at blocks of pixels and mapping them by tone and color. As such, there's a loss of quality. A high-quality JPEG can have very little loss of information, but the more you compress a file, the more information you'll lose. If you compress enough, or try to print a JPEG image large enough, you'll eventually see a blockiness in smooth tonal areas or along what should be smooth areas. The popularity of the JPEG format is due to the ability to compress a file with little data loss, allowing for many more photos to be stored on fairly small memory cards. Most major camera manufacturers generally have a best quality JPEG setting that will satisfy all but the most finicky photographers.

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