Hey you guys...don't sian the newbies lah. :sweatsm:
OK, a lens hood has many modern purposes. As some have shared here, it's to improve the image quality by shielding the front of the lens from stray light, protect the lens physically a bit and bla bla bla...
It all sounds fine and dandy, but if you're really interested in the origins of the lens hood, you would have to take a short trip back to about the time when photography was first invented waaay back.
Now, this may be a bit of a long read, but it's really interesting, if you're into such things.....
Remember the old days when cameras were like HUGE, and HEAAAVY! :sweat: Lenses were permanently fixed to the huge, boxy cameras, or even later when they were removable, they were often huge, clumsy and cumbersome affairs and impossibly slow to put on and take off from a camera for fear of damaging the delicate mechanism inside. It wasn't unimaginable for a working street photographer to carry more than 20kg of equipment on his shoulders.
Look at where the development of commercial photography flourished - mainly migrant America, even though there are various, less significant accounts of similar progress in several parts of Europe.
Now, remember that most migrants to say, the United States had to fight for 'territory' on the rough streets, which were ruled by gangs, and many could not afford decent living quarters, let alone a studio to work from!
Needless to say, crime and theft were openly rampant in the old days and the open streets were where photographers made a living mainly selling their 'portrait' photography services which was, in effect, a mini studio cum processing lab via means of a small bath-tub of clean water and several basins of chemicals to process the glass plate 'negatives'. The police, or other authorities were often useless, if not corrupted themselves.
Since their equipment were virtually immovable once set-up, they had to find a quick detach device that they could use to fend off blows from theives and gangsters, and like-wise, use as a small, indiscrete weapon. Hence, the lens 'HOOD' was born - to protect the photographers from the street HOODlums. The term 'hoodlum' is an old phrase usually used to identify a member of organised crime.
Early 'lens' hoods were in fact nothing more than simple, strong, cyclindrical metal tubes which could be quickly slipped over the arms and acted as a shield of sorts, and could be used to protect the expensive and valuable camera, as well as form a defense from the blows of a wooden rod, and can be used to 'smash' the hoodlums' faces, or heads, whichever the photographer was fortunate enough to reach in time.
It was only many centuries later (coating lenses with metal vapour fumes was not even discovered back then), long after working conditions had improved and crims had decreased, that a physicist discovered that blocking an oblique path of stray light from a prism had the effect of improving the definition and clarity of the scattered light beams that the prism created. Remember, back then 'labs' and such were often a table set beside an open window. Then, what was used to block stray light was simply heavy dark cloth.
Fast forward (i know most of you are bored to death by now; I know I am! LOL!) and some bright spark put two and two together and birthed the makings and modern use of a 'lens-hood'.
CHEERS!
ok, I made that up...but it was a fun read right? Hehehehe.....