The basic properties of a simple lens may be applied to an objective lens system as well. They will help us understand the behavior of the lens. But keep in mind the fact that optical design of a complex system is a bit more involved.
Refer to the figure above for a visual illustration of these concepts. Read more
One of the best tools available for any photographer to use to make sure your exposure is neither under or over exposed is the use of the camera histogram. It is especially important for jpeg shooters. The exposure latitude (how much the exposure can be off and still get a good image) of a jpeg is less than one f-stop. Digital SLR’s have an option for a histogram to be superimposed over the image or placed next to the image in the camera’s LCD. This histogram will provide exposure information. The image below
shows a histogram.