I highly doubt you perceive light intensity radically differently to your fellow humans... :) Most likely your monitor is miscalibrated.
Try a few different gamma calibration images from other sources (Google Images -> "gamma calibration") and if they consistently indicate that your monitor is miscalibrated, then you have your answer.
Try a few different gamma calibration images from other sources (Google Images -> "gamma calibration") and if they consistently indicate that your monitor is miscalibrated, then you have your answer.