One important parameter that has not been discussed in-depth yet is lens aperture. For anyone who is serious about their cameras, this is a term you need to familiarize yourself with. Basically, this is referring to the ratio of the focal length of the lens to the diameter of the light rays that pass through the aperture. The stopping point of the aperture can be adjusted in photography and it will change the dynamics of your imagery. You will see this measured in f-stop (such as f2.4) and this is measuring the lens opening.
So, if the number is larger (say f4.0) that means that more light is going to pass through the sensor. Thus, with a smaller aperture size, less light will be allowed to pass through.