Lens hoods are one of those accessories that are simple and easy to use that help the quality of your photos by reducing unwanted light.
They come in two varieties, soft and hard. The soft lens hood is usually just some rubber you can screw on to the front of the lens. It gets the job done, they fold up to be quite compact and you can find them for little cost. The hard lens hood is usually made from plastic or on some more expensive lenses they can be metal. Usually custom made for your lens, the hard lens hoods can often cost a lot of money for a simple piece of plastic.
So if the soft lens hood can get the job done, why pay for the hard lens hood? My favourite answer is that it will save your lens. This last weekend I broke my lens hood when I slipped on some rocks while hiking. The lens hood broke, but absorbed the force as it hit the rocks before the rest of the camera and saved my lens. This is the second time this lens hood has broken saving this lens. The previous time was a short fall and the lens landed on the hood, the hood taking the brunt of the force.
A little crazy glue and the lens hood will be back in service in 24 hours. I would recommend to anyone who has a lens with no hard lens hood to buy a hard lens hood for it. When you spend a lot of money to purchase a lens you may as well purchase the lens hoods that only increases the image quality and protects your lens.