PASM refers to a photography mode setting that determines the level of control a photographer has over their camera's settings when capturing an image. Some synonyms for PASM include manual exposure mode, aperture priority mode, shutter priority mode, and program mode. Manual exposure mode allows the photographer to have full manual control over aperture, shutter speed, and ISO, while the other three modes allow the photographer to set one or two of those settings while the camera automatically adjusts the others. Aperture priority mode allows the photographer to set the desired aperture setting, while the camera adjusts the shutter speed. Shutter priority mode allows the photographer to set the desired shutter speed while the camera adjusts the aperture setting. Program mode is similar to shutter and aperture priority modes, but the camera automatically sets ISO and in some cases, white balance.