What does IR Exposure represent in digital imaging?
Exposure index
IR Exposure is one of the two photographic properties that comprise visibility of detail, the other being contrast.
Define Milliamperage (mA).
Recording of the tube current
It represents the number of electrons moving from the cathode to the anode side of the tube per unit of time (second).
What is the relationship between exposure and milliamperage?
Direct relationship
An increase in milliamperage leads to an increase in exposure.
What is Image Receptor Exposure?
Degree of overall exposure to the image receptor
It is one of the two photographic properties that comprise visibility of detail.
What happens to details on an underexposed image?
Details are not recorded
This is due to quantum mottle/noise.
What is the recommended approach when in doubt about exposure?
Choose to overexpose the image
This can help ensure that details are captured.
What are the factors affecting IR Exposure?
- Multiple variables
- Not an exact science
- Guidelines for changes in technical factors
Variables usually balance each other.
What is the primary factor controlling IR exposure?
MAS
MAS gives the primary effect on the amount of IR Exposure.
What does an increase in MAS result in?
- Increased quantity of radiation
- Increased IR Exposure
MAS is directly proportional to exposure.
What is the Reciprocity Law?
IR exposure stays the same if overall mAs stays the same
This applies regardless of the mA station or ms used.
What are the three types of noise in imaging?
- Quantum noise
- System noise
- Ambient noise
Quantum noise is the largest contributor to total noise.
What is the main cause of quantum noise?
Inadequate technique
It causes ‘graininess’ on digital images that are underexposed.
