Week 2 Notes

Week 2 Notes - Paper Sensitometry 3/17/2008 8:01:00 AM...

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Paper Sensitometry                                17/03/2008 07:01:00 Details for Paper Sensitometry Use tungsten light source Longer exposure time (0.10 to 10 seconds) Can projection print or contact print onto paper if sensitometer unavailable Great care must be given to time/temperature/agitation because development  times are relatively short Reflection Density Defined as the log of the reciprocal of reflection o Reflectance (R) = Light reflected from image/light reflected from base o Reflection Density (Dr) = Log(1/R) Densitometer Design Prints are usually illuminated at 45 degree angle and view from perpendicular ANSI has standardized this for reflection densitometer design Methods of Use Two calibration options o Zero on unexposed processed paper – Base + Fog is then removed  from all readings o Zero based on white reference (magnesium oxide) – Base + Fog is still  present
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Paper Curves Paper Curves differ from Film in 3 ways o Toe is usually longer and extends to a high density o Slope of straight line portion is steeper and if present is shorter than  film o Shoulder quickly reached maximum density rarely reached 2.1 These 3 things cause Useful Log Exposure Range of photographic paper to  be substantially less than that of pictorial film
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Paper Curves Purpose of paper is to receive transmitted tones from negative
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o (Purpose of film is to receive reflected tones of original scene) When evaluating contrast of photographic paper there are two important  pieces of information o Useful log exposure range (input) o Total density range (output) Total Density Range Range from paper B+F to the maximum obtainable density (maximum black) Paper B+F range is from 0.01 to 0.03 and is based on the whiteness of the 
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Week 2 Notes - Paper Sensitometry 3/17/2008 8:01:00 AM...

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