Which of the following statements about dental radiographic exposure variables is true?

a. Increasing the mA darkens the radiograph.
b. Decreasing exposure time darkens the radiograph.
c. Exposure time is difficult to change on most machines.
d. Milliamperage affects radiographic contrast.

a. The mA setting determines the quantity (number) of x-rays produced. Increasing the mA darkens the image, while decreasing the mA lightens the image. Exposure time also determines the quantity of x-rays produced, so increasing exposure time darkens the radiograph, while decreasing the exposure time lightens it. Exposure time is the easiest exposure control to change. kVp primarily influences image contrast.