Quality & Faults Flashcards
Definition of density
Factors affecting this
Degree of film blackening
Exposure and processing
What influences exposure
Mainly mAs
Also kv
What happens if mAs too high
What does film look like
Overexposed
Film too dark - markers remain white
What happens if mAs too low
What does film look like
Underexposed
Film will be pale
- if contrast high, kv also too low
Reasons for underdevelopment (3)
Diluted/exhausted developer
Developer too cold
Development time too short
What will underdevelopment film look like
How to test
Uniformly pale with low contrast
Finger test
Reasons for overdevelopment (2)
Developer too hot
Film developed for too long
What does overdeveloped film look like
Uniformly darkened - markers not visible
What factors influence contrast
Voltage
Underdevelopment
Define contrast
Visualisation of varying densities
Reasons for high contrast
Underexposed
Kv too low
Reason for low contrast
Underdevelopment
Reason for NO contrast
Kv too high
Define definition
Sharpness and clarity of structures
Factors which affect definition (7)
Movement Scatter Fogging Poor film-screen contact Film-screen speed Focal spot size FFD
Effect of scatter on film
Random darkening
Loss of definition and contrast
What may cause fogging (5)
Scatter Overdevelopment Prolonged storage Unsuitable sage-light filter Accidental exposure to Rx/light
Effect of film-screen speed on definition
Increased speed reduces definition
Effect of focal spot size on definition
Larger FSS will reduce definition due to penumbra effect
Effect of FFD on definition
Larger FFD resulting from object going as close to film as possible results in better definition
Most common film fault
Underdevelopment
Reasons film may be too dark (4)
Overexposure
Overdevelopment
FFD too short
Fogging
Reasons film may be too light (3)
Underexposure (high contrast)
Underdevelopment (low contrast)
FFD too long
Causes of patchy density or air bubbles
Developer not stirred or film not agitated
