Lens hoods protect against uncontrolled, stray light and unwanted reflections which result in reduced contrast and ghost images. In general, the use of a lens hood is recommended because better contrast improves the appearance of the photograph. The 52mm Lens Hood will also shield the front lens element against rain and mechanical damage. The main function of the Alloy Lens Hood is to shade the lens from stray light, improving your contrast and image quality. But 52mm Lens Hood will also protect the front barrel from the inevitable impacts against walls, door frames, and other real-life obstacles and in inclement weather. It can assist in keeping moisture or wind-blown debris off the lens.
Other Thoughts:The 52mm version is great because it adds only minimal diameter to the lens. You can pull it out big time and for storage it folds back easily. Don't worry about deformation, it stays stable enough to not be in the frame, no matter how much you miss-treat it. And for the price you can replace it in a couple of years when it should dry out or whatever.
Other Thoughts:I bought this odd looking hood for my Canon 50mm 1.8 because many reviews said it was the most suitable given the known weakness of the front element. Before getting it I was afraid it would be harder to expand and retract, but it's ok. The texture is also great avoiding light reflection.