Pretty straight forward question. What does a lens hood do?
1See photo.stackexchange.com/questions/399/… - some good answers there– ReidJul 16, 2010 at 19:37
A lens hood has two purposes - one is to shield the lens elements from stray light - either directly from the sun, from passing cars, from a flash, etc. This stray light can cause lens flare and reduced contrast, so it is best to limit it.
Its also useful for avoiding bumps to your lens or filter. I use mine a lot in the car, because my lens is always very close to the window.
(It can also make that huge telephoto look that much more impressive)
Another advantage when shooting close to a window is that you can press the lens hood up against the glass, and block out any light from the camera side of the window and reduce reflections.– EddJul 22, 2010 at 15:57
4Impressive-looking telephotos are very important in situations where you have to look like serious photographer, for example if you're trying to get past security into press sections on a show or sports event.– cheJul 22, 2010 at 16:16
2It also helps to keep rain off the front of the lens.– vclawAug 3, 2015 at 12:29
Do I need hood in conical petal form to make product photography in white shooting tent outside when sun is shining? Now same question except that do I still need to have hood on when making same photography indoors with limited lighting source? I have Panasonic G5 with 14-42mm lens kit.– Boris_yoOct 10, 2015 at 12:04