Photography is all about light. To get the exposure of our picture right, we need to balance the aperture size and shutter speed. This can become tricky in low light situations. If both aperture and shutter speed don’t suffice to get the exposure right, we can increase the ISO value. The ISO value is a measure for the sensitivity of the sensor. ISO stands for International Standards Organization.
To let the sensor of our camera capture an image, we have to feed it with light. Through the objective, i.e. a lens system, we project an image on the sensor with a chosen Depth Of Field (DOF). With the shutter speed we determine how long we will feed the sensor with light.