Lens hoods (or shades) are used to prevent stray light from hitting the sides of the front lens element. Undesirable angles of light can lower the overall contrast of a photograph and cause glare and lens flare.
A lens hood is a tube or cone which attaches to the front of the lens, either clipping onto the outside, attaching with a bayonet, or screwing into the lens thread (size marked with ø and mm). They come in either metal, plastic, or rubber, and should have a black antireflective surface. They are available in various shapes including round, rectangular, and tulip (or petal).
Round lens hoods are simple cylindrical sections that extend beyond the front of the lens.
Rectangular lens hoods are generally more efficient than round hoods. Their shape closely resembles the format of the recorded image so they can be longer than cylindrical lens hoods without blocking the lens’s angle of view (AOV), which would cause vignetting. Vignetting by a lens hood is called mechanical vignetting. It usually results in an abrupt transition from bright to black in the corners of an image.
Tulip lens hoods (also known as flower or petal hoods) have a more complex design: a cone with four shapes cut out to avoid blocking the corner points of a photo. This type of hood delivers the best possible shading effect for zoom lenses, as the AOV of a zoom lens is variable according to the focal length being used. Tulip hoods provide a compromise for getting the best shade at long focal lengths, while the cut-out portions of the hood prevent the lens hood from intersecting with the AOV at short (wide angle) focal lengths, thereby reducing the amount of vignetting in the final image.
The AOV of the lens is a vital consideration when choosing a lens hood. If a lens hood designed for a telephoto lens was used on a wide-angle lens, it would block part of the scene, especially the corners of the frame. If a lens hood designed for a wide angle lens was used on a telephoto lens the hood would have no effect and stray light rays would still be able to hit the sides of the lens. One should therefore choose a dedicated lens hood that is optimized to provide the maximum shading for the specific focal length of the lens being used.
When using a rangefinder, it is important to consider the length and size of a lens hood, not only to avoid blocking the corners of the recorded image, but also because they can block the bottom right corner of the view in the viewfinder. Vented lens hoods have openings around the lens and taper inward, minimizing the amount of hood that can obstruct the framing of the picture in the viewfinder. Below is a basic guide to the use of the specific hood types:
Shallow hood |
wide-angle to normal lens |
Deep hood |
telephoto lens |
Tulip hood |
wide to telephoto zoom lens |
Vented hood |
rangefinder camera |
When using a screw-in hood in conjunction with a stepping ring or filter, remember that they will slightly extend the length of the hood and could cause it to encroach on the AOV. Lens hoods may also be used to protect the front lens element from accidental impact.