Time and again I get asked by those starting out in photography, “What is this thing that came with my lens?” What they are referring to is the lens hood included with most new lenses. For those new to cameras and lenses, it looks odd as it is often cut in a wave-like pattern.
A lens hood’s main purpose is to block light. If the lens is a prime lens (fixed focal length, non-zooming) the hood will resemble a tube, often larger at one end than the other. For zoom lenses the hood will have a curved opening at one end. This curve is cut to the zoom range of the lens and allows for the wider field of view afforded smaller focal lengths, while still attempting to block most light at a longer focal length. It’s a compromise that matches the compromise of a zoom lens.
Does the hood actually help?
Yes and no.
The hood will help block out light that is coming into the lens and causing flare by striking the outer lens elements (the glass pieces that make up the entire lens) at a less than optimal angle. This is light that never would have made it to the sensor and isn’t needed. Instead, it causes those discolored spots you might have seen, shaped like the lens aperture (typically a hexagon or octagon). While lens flare also occurs from light coming directly into the lens, flare from off-angle light can be prevented.
The “no” part of the answer is in regards to zoom lens hoods. With a fixed focal length lens, the hood is solid and often coated with felt on the inside, blocking out the maximum amount of light possible (the felt helps reduce reflected light from the plastic hood). But with a zoom hood, the curve can allow light in sooner than if the lens was fixed, although not that noticably so unless shooting in vertical orientation and with the lens pointed close to the sun
A quick, simple demonstration of shots with and without a hood. First with:
And then without:
In this case the sun was close to its maximum height in the sky and these photos were taken with a Canon 7D and Canon EF 10-22mm lens. You can see the flare at the bottom and you can also see how some of the dust on my lens has been highlighted.
Should you always use a lens hood?
No, but with an explainaton.
A lens hood will not help you when the sun (or light source) is actually in your shot. While it can help reduce extra light from reflected objects nearby (windows, white walls, etc.), the effect is minimal.
But in reality, you should use the hood whenever you can. My reason for wording the answer this way is so you don’t freak out if you forget your hood or it is hard to pack (many wide angle lens hoods don’t always fit in the holes in camera bags). If you happen to be missing your hood for the day, simply use your hand, a book or any other likely object to block out the flare from the main light source, while making sure you don’t get the shading device into the picture. This won’t block the reflected light, which can minutely soften a photo (not to a point most of us will ever realize, mind you) but it will help take care of the main flare issue.
What has been your experience with using hoods in the field? As always, be respectful of others while helping to raise the knowledge level of all our great readers in the comments section below.