Lightmeter Pro is an app that simulates a digital meter. This app allows you to check the exposure settings of the analogue and digital cameras to get the best exposure of the picture taken.
the lightmeter Pro settings allow you to set the method for calculating the exposure in manual mode (MANUAL), where you can manually set the time values (T) (shutter speed) and the (F) (Aperture) according to the ISO sensitivity value.
Mode (APERTURE), "APERTURE PRIORITY" allows you to manually set the "Opening of the lens" and LightMeter Pro calculates the value of shutter speed.
The mode (SPEED), "TIME PRIORITY" lets you manually set the value of shutter speed and the app calculates the relative value of Aperture (F).
Among the various options in addition to the ISO sensitivity value, you can set the focal length of the lens used. this parameter allows you to automatically set the maximum aperture value corresponding to the family of lenses. The f / stop value set is an indicative value could be different for lenses of the same focal length, but less or more bright.