Professionals and serious amateur photographers alike know that lens hoods are an important part of the lens. A properly designed lens hood shades the lens’s front element or protective filters, from stray non-image producing light. The stray light can bounce around inside the lens and reduce contrast as well as create flare (if sufficiently close to the lens’s field of view).

Lens hoods help to minimize those effects, but they have to be designed for the lens’s field of view. However currently many photographers are using smaller crop sensors with lenses with lens hoods designed for 135 format film. For example, the Canon EF 28-135 f/3.5-5.6 IS USM that comes as part of one of the Canon 50D kits, was designed to be used with a camera with a 35mm film size frame. As such the lens hood is designed to shade the field of view of a 28mm lens when there is a 35mm frame behind it. But on the 50D, the lens at 28mm has a much narrower field of view, in fact it’s equivalent to a 45mm lens on a full frame camera. In this case you can shade more of the lens with out vignetting showing in the image.

Anyway in the link below, David Burren has put together a table of possible alternate lens hoods for use on EF lenses when used on APS-C (1.6 crop) and APS-H (1.3 crop) Canon bodies. Keep in mind, not all lenses can be adapted, so if your lens isn’t in the list, it’s quite possible there isn’t an alternative hood available for it. Also note, EF-S lenses and lenses designed for crop format digital bodies (like Sigma’s DC line) have lens hoods designed to shade the lens as much as possible on a crop format body.

David Burren Photography: Alternate Canon lens hoods