Tuesday, January 30, 2007
November 2004 HelpLine
Buffer: This is a term used with digital cameras that's similar to memory in your computer. Think of a buffer as a waiting area, where each image is temporarily stored before it gets written to your memory card. The larger the buffer in a camera, the more images you can capture until the camera stops you and has to finish writing the data to the memory card.
Dispersion: You hear this term when dealing with optics. Manufacturers talk about low-dispersion (LD) glass. Dispersion is the separation of light into its different color components as it passes through an optical medium. Put another way, Judy Garland was singing about dispersion in "Somewhere Over the Rainbow." Manufacturers use LD glass to reduce color fringing and improve the overall sharpness of the image.
Dot (or pixel) pitch: This term is used to indicate the sharpness of a computer monitor. Manufacturers can't use the word "resolution," since that setting is determined by the video card (1024x768 will display as 1024x768 on all monitors capable of displaying that resolution, for example). Dot pitch is the measurement, in millimeters, of the distance between phosphor dots (or LCD pixels) of the same color in a display. The smaller the number, the sharper the image. Keep in mind that dot pitch is only one factor in determining display quality.
Dynamic range: This is a term often used when discussing scanner performance. Dynamic range is the measurement of the scanner's ability to resolve the full range of tones. The scale used for this specification goes from zero to 4, with zero being full white and 4 being full black. Dynamic range can be shown as two numbers, represented by the terms Dmax and Dmin, or it can be noted as a single number, which is the difference between Dmax and Dmin. The higher the dynamic range number, the greater the ability of the scanner to see details in both the lighter and darker areas of the image.
EXIF: The acronym stands for exchangeable image file format, which allows for the storage of image data in the image file itself. A whole host of information, including the shutter speed and aperture you used for exposure, as well as the lens focal length, is stored in a special location in the image file. The "exchangeable" part means that even though the data was created in the camera, image-editing software from different manufacturers can read it.
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