On the first generation Lytro camera, when both Shutter Speed and ISO Sensitivity have been set manually, a number will appear in the top center of the screen, which indicates the Exposure Value (EV). The Exposure Value combines the Shutter Speed, the ISO Sensitivity, and the position of the ND Filter, into a single numerical level of light exposure. As the number gets higher (more positive), the picture will become brighter. Similarly, as the number gets lower (more negative), the picture will become darker.
NOTE: This article applies to the first generation Lytro camera only.