Aren't they called bellows or something? What are they meant for?
Bellows are traditionally used to pump air into a furnace such as one used for forging to get the flames roaring again by introducing more oxygen. They would also use bellows to get higher temperatures for forges when a blacksmith was doing work in them.
Answer by Cody on 06 Jan 2010 01:11:08You mean the cone or flower shape extensions sometimes seen on the front of a lens? They're called lens hoods. Their main purpose is to prevent light from striking the lens from the sides, as this could result in glare or flaring. They can also offer some protection. The only drawback is that an attached hood might cast a shadow while using flash (particularly with the on-board flash).
Answer by AWriterWandering on 06 Jan 2010 01:30:19Do you mean bellows as in the bellows on lenses? They allow you to move a lens towards or away from the film plane in order to gain magnification beyond the standard 'macro' of 1:1. With bellows and extension tubes, you can reach about 20x lifesize magnification.
They also allow lenses to become tilt-shift lenses to correct converging verticals.
[URL Truncated] might give you an insight.
Are you thinking of a lens hood?
They are put on the end of DSLR lenses to help block out some unwanted light and they also help protect the front of the lens from the weather and scratches.
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