Polaris SPD100 Digital Exposure Meter Oversized LCD display shows all data and functions clearly and easily, even at full arm's length. Large analog" (Gas-Gauge Style) Scale for easy fractional measurements. Standard PC terminal for sync cord flash activation. Compact, ultra-thin design. Polaris is less than 1- inch thick and weighs just 4 oz. Requires only one "AA" battery. (Not included) Four exposure modes to choose from. Unique multi-flash feature makes it simple to calculate how many times the flash must be fired to achieve a desired f/stop. Accurate to 1/10 f-stop.