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Sensitometry
the measurement of the characteristic responses of film to exposure and processing
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The measurement of the characteristic responses of film to exposure and processing
Sensitometry
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penetrometer
a device with a series of increasingly thick uniform absorbers used in teh monitoring of x-ray equipment, film, and film/speed combinations (step wedge)
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a device with a series of increasingly thick uniform absorbers used in the monitoring of x-ray equipment, film, and film/screen combinations (step wedge)
penetrometer
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a device used to expose a reproducible, uniform, optical step wedge onto a film used for processor monitoring or film comparison
senistometer
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sensitometer
a device used to expose a reproducible, unform, optical step wedge onto a film used for processor monitoring of film comparison
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densitometer
and instrument that provides a readout of the amount of density (blackening) on a film
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an instrument that provides a readout of the amount of density (blackening) on a film
densitometer
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optical density
the density viewed on an x-ray film
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the density viewed on an x-ray film
optical density
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optical density is determined by what formula?
- OD= log10 Io/It
- Io= intensity of incident light
- It= intensity of the transmitted light
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opacity
the ability of the film to stop light
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the ability of the film to stop light
opacity
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what is the opacity formula?
Io/It
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the D log E curve, or H&D curve, or characteristic curve, or the sensitometric curve
a graph of the relationship between hte amount of exposure and the resultant density on the film
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a graph of the relationship between the amount of exposure and the resultant density on the film
the D log E curve, or H&D curve, or characteristic curve, or the sensitometric curve
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base plus fog
the density inherent in the film and the fog that is produced by processing (no exposure)
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the density inherent in the film base and the fog that is produced by the processing (no exposure)
base plus fog
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toe
subtle gray tones in early development mostly controlled by phenidone
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suble gray tones in early development mostly controlled by phenidone
toe
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straight line portion
between toe and shoulder - most of the diagnostic quality information is on this portion of the curve between OD .5 and 1.25
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between toe and shoulder - most of the diagnostic quality information is on this portion of the curve between OD .5 and 1.25
shoulder
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Dmax
maximum density the film is capable of recording. Any exposure above this will result in less density (reversal or solarization)
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maximum density the film is capable of recording. Any exposure above this will result in less density (reversal or solarization)
Dmax
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film characteristics
resolution, speed, contrast, latitude
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resolution, speed, contrast, latitude
film characteristics
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resolution
not analysed by sensitometry, the ability to accurately image an object also called detail, sharpness, definition, or resolving power, measure by the ability to see line pairs - unit of resolution is liine pairs per millimeter expressed as lp/mm
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not analysed by sensitometry, the ability to accurately image an object also called detail, sharpness, definition, or resolving power, measure by the ability to see line pairs - unit of resolution is liine pairs per millimeter expressed as lp/mm
Resolution
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resolution is determined by (2)
- 1. size of silver halide crystals - inverse relationship: larger crystal the lower resolution, smaller crystal the higher the resolution
- 2. usually controlled by the size of the intensifying screen crystals
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speed
the amount of density a film produces for a given amount of exposure controlled by phenidone because this affects the toe of the D log E curve and thus when the straight line portion of the curve begins. Determined by the size of the silver halide crystals and the number of sensitivity specks and the thickness of the emulsion
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the amount of density a film produces for a given amount of exposure controlled by phenidone because this affects the toe of the D log E curve and thus when the straight line portion of the curve begins. Determined by the size of the silver halide crystals and the number of sensitivity specks and the thickness of the emulsion
speed
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speed point or speed exposure point
density of the DO 1.0 + b+f on the curve
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density of the OD 1.0 + b+f on the curve
speed point or speed exposure point
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Difference in film speed formula
- antilog (log E1 - log E2)
- log E1 is the log exposure of the 1st film
- log E2 is the log exposure of hte 2nd film (see page 321 + 322)
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relative speed formula
1/ exposure in R needed to produce speed point density (OD 1.0 + b+f)
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speed is affected by
immersion time, temperature, and chemical activity
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immersion time, temperature, and chemical activity affect what?
speed
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contrast
the difference between adjacent densities
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the difference between adjacent densities
contrast
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density will only affect contrast when ___ or ___ the ___ ___ ___ or hte curve
above, below, straight line portion
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what will only affect contrast whe above or below the straight line portion of the curve
density
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the slope of any portion of the D log E curve
Gradient point
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Gradient point
the slope of any portion of the D log E curve
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Average Gradient
overall radiographic film contrast
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overall radiographic film contrast
average gradient
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average gradient formula
- D2 - D1 / E2 - E1
- D = a constant of 2.25
- e= the exposure that produces D
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latitude
the range of exposures that will produce densities within the diagnostic range - between .25 and 2.50
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the range of exposures that will produce densities within the diagnostic range - between .25 and 2.5 (I thought it was 2.25...)
latitude
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latitude formula:
- Eh - El
- Eh = high point
- El = low point
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latitude and contrast are ___ related, as contrast ___, latitude ___. As contrast ___, latitude ___.
inversely, increases, decreases, decreases, increases
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