Chapt 29 Viewing the Digital Image Photometric Quantities Hard/Soft Copy Active Matrix Liquid Crystal Display Pre/postprocessing digital image PACS

Photometric Quantities Response of the eye Photopic Scotopic

Luminous flux Total intensity of light from a source Measured in “luminous flux in LUMENS

Illuminance Intensity of light incident on a surface Goes back to measure of “candle light” on a single square foot of surface

Luminance intensity Amount of light emitted by a light source (viewbox is a good example)

Luminance Measure of the BRIGHTNESS of a source (like in a digital display) Measured in candela per meter squared = NIT

Cosine Law Relate to inverse square law and the amount of radiation at varied distance Same for light at GREATER distances like the CR vs periphery of the beam (pathagoras theory)

Hard-soft copy Hard = radiograph on film Soft = Viewing on a cathode ray tube (computer/T.V. monitor)

Active Matrix Liquid Crystal Display Instead of using a “cathode ray tube” (TV tube type) viewing system, the active matrix, pixel by pixel, viewing monitor is used Spatial resolution improves with larger matrix (pixels) displays

Preprocessing the image YOU can program the computer with what YOU want the image to look like i.e. do we want a hand with a dynamic range of 2? Perhaps a CXR with a dynamic range of 60? Show what scale of contrast and shades of gray to display

Postprocessing Annotation Window and leveling (expand or shrink the shades of grays)

PACS Aaron – tell your thing!