Light sensors or sensors of light are often referred as types of photodetectors or photosensors. There are several varieties of these sensors. Light sensors detect light density but do not record images. Most common light density sensors are: Photodiodes (LDR Light Dependent Resistors) and photoresistors (LDR Light Dependent Resistors). Photo diode is capable of converting light into either current or voltage. Photo resistor is a resistor whose resistance decreases with increasing light intensity.