Compute a sensor's minimum photometric exposure (lux-sec) to obtain a 30dB SNR thirtyDBLevel = sensorMPE30(sensor) If sensor is not defined, the current sensor settings are used. This level is of interest because observers can just barely detect 3 percent (30dB) noise in a uniform image. Hence, we use this lux-sec level to determine the noise threshold. If no output argument is requested, a graph is produced of snr vs. lux-sec and the MPE30 is in the title. Otherwise, the thirtyDBLevel is returned and no plot is generated. See also: sensorSNRluxsec Example: sensorMPE30 Copyright ImagEval Consultants, LLC, 2003.