absolute white
in theory a material that perfectly reflects all light energy at every visible wavelength; in practice a solid white with known spectral data that is used as the "reference white" for all measurements of absolute reflectance.
Notice that in each example the darks get darker and the lights get lighter, but that absolute black and absolute white stay where they are.
HOW TO: Unsharp Mask (USM)
Get to Unsharp Mask via Filter > Sharpen > Unsharp Mask.
TONAL RANGE - The various shades of gray between solid black and absolute white.
5 stops above mid-toned (take this as read for now, I cover it in more detail in the next section). Strangely, my Canon 30D's exposure dial only covers 2 stops, so I have to use manual mode if I need absolute whites or blacks.
 See also: Angle of view, Digital, Exposure, Film, Focus
  
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