UMAX Technologies Astra 2000U - Manual (Page 112)

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PMT (Photo Multiplier Tube)-The method of light and image
capture used by drum scanners. This method is considered to be
superior to CCD technology and usually has a higher Dynamic
Range than CCD’s. UMAX CCD technology is moving closer and
closer to PMT technology every day.
Postscript-A device independent image file format. This is the file
format most commonly used to output images or compound
documents, pages with text and graphics, via the four-color process.
Postscript color is currently limited to 24-bit pixel depth or 16.7
million colors. Grayscale PS images are limited to an 8-bit pixel
depth.
PPI (Pixels Per Inch)-This measurement is the same as DPI or Dots
Per Inch. PPI is more indicative of a monitor where DPI is usually
associated with printers and scanners.
Reflective Object-An original image that doesn't allow light to
pass through. A printed photograph is an example of a reflective
image.
Resolution-Refers to how many pixels a device can create or how
many dots a device will reproduce.
RGB-Red (R), Green (G) and Blue (B) or the additive primary
colors.
RIP (Raster Image Processing)-The process of converting pixels to
halftone spots or dots. A RIP can be part of the printer or a separate
computer if speed is of the essence.
Screen-Refers to computerized and non-computerized methods of
converting a continuous tone image into printable patterns. Screen
frequencies are usually referred to as LPI.
SCSI (Small Computer Systems Interface)-Currently the fastest
protocol for transferring information from a peripheral device, such
as a scanner, to the computer.