3.3. Variations

Adding a light-level sensor to the Arduino allows it to skip taking photos when it's too dark, which can be very handy if you're making a movie outside that you can't light artificially at night.

Light-dependent resistors (LDRs) vary their resistance inversely to the amount of light that is falling on them: in other words, in bright light they have very low resistance and allow a current to flow, while in darkness they have very high resistance and prevent current from flowing. The schematic shows how to add an LDR so that it can be read using an analog input to detect the current light level.