It is no surprise that manufacturers are constantly inventing new gadgets and gizmos for us to buy. Very occasionally you may find a new gadget that may improve your picture taking experience. Note that we wrote "experience" not "pictures".
For those of us who like to hoard gear. The latest introduction is a pancake lens.
First, what is a pancake lens? Before we get into that let's define what a pancake is for the international readers. A pancake is a breakfast cake that is usually circular and very flat, much like a French crepe but usually smaller and thicker than a crepe. So a pancake lense is a lens that is very flat and compact. It is a fixed focal length lens or better known as a prime lens in today's terminology. Which means it has no zooming capabilities. In the current crop of pancake lenses you will also find that not only is it a prime lens but that the lens only has one f/stop. In other words it really only does one thing. The combination makes it very very compact.
But what are the pros and cons of these lenses?
First the pros. They are very small and very compact. They can be very sharp. They can be very fast; meaning the aperture can be very wide and therefore gather more light allowing you to shoot with faster shutter speeds. Most pancake lenses are very inexpensive such as the Canon 40mm f/2.8 which is $150. They also look kinda sexy with their tiny size!
The cons: They only have one focal length. Unless you have developed a particular style of shooting where you find that you are shooting with a particular focal length most of the time, it's difficult to make prime lenses work in many situations. The lens only has one aperture setting which means you are further hamstrung; in other words it may be difficult to pull a slow shutter speed in the middle of the day (say you want a long exposure for that waterfall). It also means that you can not create an under exposed image because most cameras today can not shoot a shutter speed faster than 1/2000 of a second; and in the middle of the day with a f/2.8 you may need to head towards 1/5000 if you want an underexposed image.
If you are shooting in a controlled environment (like a studio with a tripod) this lense can be very good for you, but surely that defeats the purpose of a pancake lens, in that it was designed to be light weight astensibly used for traveling.
You will have to decide which is best for you.