A pancake lens has nothing to do with the tasty breakfast food that you put maple syrup and cream on. However, the name is derived from the loose resemblance that a pancake lens has to an edible pancake. It is camera lens that is convex and fairly flat, hence the name.
Pancake lenses are compact and lightweight and can fit onto single-lens reflex (SLR) cameras as an alternative to larger lenses when space or weight are important factors. Using a pancake lens means you can keep the lens on the camera ready to take photos because the camera casing is usually large enough to fit over the flat lens. A pancake lens usually has a fixed focal length, so you can't zoom in or out.
Pancake Lens Aperture
The aperture of a pancake lens is wider than larger camera lenses. This means it can take in more light than lenses with adjustable focal lengths. As more light is taken in, you can increase the speed of the shutter. This results is much less camera shake, especially in conditions of low light where you would normally need to use a tripod if you were using a longer lens.
A pancake lens can be used to take photos in various conditions. For example, it's capable of taking a reasonable landscape photo, but can also be used for portrait-type photos because it has a fairly wide angle and adequate depth of focus. It can also take quality interior photos without the need for a flash.
Balancing Limitations and Benefits
If you want to take wide scenic photos, then a pancake lens has its limitations, but for a standard photo of a vacation vista, it does the job perfectly. A pancake lens has a fixed focal length and cannot zoom in, but you can get surprisingly close to an object and have it remain in focus. Overall, a pancake lens allows you to take many types of photos quickly and simply without having to carry a selection of lenses.