24 Sep This underexposure is likely due to improper radiographic technique (mAs too low) or Automatic Exposure Control phototimer malfunction. A repeat exposure of the same patient is shown in Figure 4, clearly demonstrating improved image quality and diagnostic information not shown in the underexposed. Exposure factors. Radiographic Exposure Settings (1). Milliamperage (mA). Amount of electrical current applied to cathode; Affects number of X-rays produced; Usually combined with time (s) to enable mAs to be altered as a single setting; Alters the overall brightness of the image (overall more 'light' or 'dark'); Higher mAs. 7 Aug Exposure parameters and patient thicknesses were assigned 'units' and an increase in one 'unit' equals a doubling of exposure. 3. It fails at the extreme ends of the kVp range (40 and kVp). 4. Variable kVp technique, 4. The mAs is kept constant and the kVp is adjusted. An increase of 2 kVp is required.