Lens Hoods
Image © John Clements
I am often asked by those new to photography about the role and use of a lens hood. To cut to the chase, using one except in very few situations is sound advice.
What a lens hood will do is similar to the effect we get when we place a hand to shield our eyes in strong sun. By doing that we stop light coming from extreme angles into our eyes, which on a bright day makes us squint and be uncomfortable let alone reducing the detail we perceive. Instead we can get dramatically clearer vision because only the light coming from the direction of subject and not elsewhere are what we want, and we then get.
The same happens to a lens and the way it records an image, except those light rays not coming from a subject cause a digital camera or film to record at best lower contrast, but often lens flare. Neither is desirable, as they reduce detail and apparent punch (contrast) in the result. Lower contrast leads to loosing something even if it is sometimes barely noticeable in the image. Sometimes we can put it back in post capture, but if we get more noticeable lens flare, thats more of a problem.
A couple of points worth considering are that with a zoom lens, the lens hood that is supplied or made as a separate accessory is designed only for the shortest (widest) focal length. This is because any hood made for a longer focal length setting would cause vignetting at any wider angle shot. Vignetting the term given to a fall off of illumination reaching the outer parts of a picture and would in these situations be quite noticeable compared to the more central part of a shot. If you want you could improvise for longer than the widest settings with some black card, making it a bit longer, but that would take some test shots to get the right length.
Any hood is better than none when we have brighter light. In the last few days we have had some wonderful strong winter sunlight. That coming from a side angle can enhance for example the relief of the land in a landscape, but it is worth restricting it from falling directly into the lens to maximise this potential detail. It is o the subject not the lens we want its benefits.
The better hoods are serrated on the inside to create more of a light trap, and even ‘flocked’ with a velvet like material. But a manufacturer has to balance design with cost and often because of the lens design a simpler design may well suffice. There are some third party products that are a bellows design, so we can adjust the length of bellows to suit different focal lengths.
If you have a fixed focal length lens than the hood is of course made with an easier task in mind. Even so, with any lens sometimes making your own ‘extension’ can add to what the supplied lens hood can achieve.
Image © Canon Corporation
The only time I would suggest not fitting your lens hood is when you are using a built in flash on your camera and photographing a very close subject. As a pop up flash does not raise itself very high, some of its light does not reach the subject but hits the lens hood or sometimes the lens barrel itself. And while on the subject of close-up, if you are capturing a macro or micro shot, then not having the lens hood on may enable you to introduce some light from a flash or a reflector between the lens and subject.
And finally, a lens hood is a good way to protect your front element of a lens from impact damage as the hood often gets in the way. Its better to trash a lens hood (although not always easy) than a front element. The latter can be very expensive to replace. I do not use protective filters over my lenses anymore, so a lens hood is important for this reason alone.
