Why a flower?


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ndroo-

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#1
Why are those hoods shaped like a flower? Are they just round ones available? Why need to have them look like flowers? :D
 

coke21

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#2
ndroo said:
Why are those hoods shaped like a flower? Are they just round ones available? Why need to have them look like flowers? :D
The flower ones are made in such a way to prevent fall off for the lens. You will probably realise that the flower ones usually accompany the wider lenses.
 

ndroo-

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#3
coke21 said:
The flower ones are made in such a way to prevent fall off for the lens. You will probably realise that the flower ones usually accompany the wider lenses.
err .. don't get u ... :) prevent fall off?
 

PLRBEAR

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#5
*Pic not available, so just read from article.


Figure shows lens the occurrence of lens flare and the usefulness of a proper lens hood. There is a regular light ray that belongs to the photographed scene, this is the blue ray that arrives within the lens angle of view indicated by the brighter gray. This ray is normally refracted and contributes to the image formation. (Note however that I did not attempt genuine ray tracing, the light paths in figure 1 are merely illustrative.) There is also a slanting ray of sunlight that impinges upon the front element when a lens hood is absent. A small part of the light is reflected from the rear surface of this element (red arrow). A fraction of this light is reflected again from the front surface, directed to the film (dashed red line). This is flare.

Version 1.6
© Paul van Walree
 

PLRBEAR

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#6
I believe fall-off is also another name for vignetting. Which is the unintended darkening of the image corners in a photographic image. Please correct me if i'm wrong. Thanks.
 

coke21

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PLRBEAR said:
I believe fall-off is also another name for vignetting. Which is the unintended darkening of the image corners in a photographic image. Please correct me if i'm wrong. Thanks.
Sorry, correction not for fall off but for vignetting. You can read more about it here

http://www.vanwalree.com/optics/lenshood.html

Althought fall off and vignetting might have similarities, don't think they are caused by the same thing.
 

ndroo-

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#8
thanks. the info from the link is great for a newbie like me :) cheers
 

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