6.2
High and Low Contrasts
A high contrast is a dental image that has very dark areas and very light areas. A low contrast is a dental image that does not have very dark and very light areas but instead has many shades of gray.
Film and Subject Contrasts
The overall contrast is determined by film contrast and subject contrast. Film contrast is the inherent qualities of the film, determined by the manufacturer and processing techniques (which are more influential when using traditional film). Subject contrast is the characteristics of the subject that influence radiographic contrast in size and thickness of the patient’s tissues.
Scales of Contrast
The range of useful densities is short-scale contrast (high contrast) and long-scale contrast (low contrast).
A short-scale contrast is a radiograph with only two densities, black and white, and it occurs when machines function at low kVp. For long-scale contrast, it is a radiograph with many densities, many shades of gray and occurs with machines functioning at high kVp.
Practice Makes Perfect
Exercise: Complete KVP and mA chart identifying the factors influencing image quality. The chart can be found on Blackboard and downloaded and printed for completion. See Table 6-1 Visual Characteristics and Influencing Factors: Iannucci & Howerton: Dental Radiography Principles and Techniques, 6th Edition, (Pg. 51).
Media Attributions
- Iannucci & Howerton: Dental Radiography Principles and Techniques, 6th Edition, Chapter 6, CC BY-NC-ND
