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Old Aug 18, 2004, 12:09 AM   #1
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can someone explain why a petal-hood could come in useful, and in what real-world shooting environment would i desire one, and what environment would i NOT want to use one......



i understand it is supposed to block refracting light from distorting the image, but under what conditions does this become an issue?

thanks much!

a.
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Old Aug 18, 2004, 5:31 AM   #2
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The reason for a lens hood is to reduce a type of flare caused when strong light hits the front lens element at a shallow angle. This Flare generally manifests itself as a lack of contrast giving pictures a dull lifeless appearance. (When shooting into the light source the hood serves little purpose but the flare effect is usuallydifferent in this case, not washing out the picture so badly and sometimes showing the little aperture shaped bright spots.)

The petal shaped lens hood gives the maximum protection from flare while eliminating the possibility of vignetting. A round hood is a compromise, especially on a wide angle lens, since it must be small enough not to appear in the corners of your picture (vignette) it is therefore not very effective. The petal shape puts the notches in the corners so that they do not cause vignettes but can extend forward far enough on the top, bottom and sides to block out more of the errant light which causes flare. These are especially important on big zoom lenses since flare is more of a problem at the long focal lengths so we see the petal shape which prevents vignettes at the wide end while offering some protection at the long end. Longer zooms with no wide angle setting will often have round hoods since the angle of view is so small that vignetting is not an issue.

BTW when using your camera on a tripod a simple shade from any object can reduce flare without causing other issues. (some people just use a card or even a book or magazine held out of the lenses field of view,to prevent the sun from falling directly on the front lens element).

I hope this answers your question.

Ira
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Old Aug 18, 2004, 3:00 PM   #3
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Monza ~! BTW, saw your website - impressive kowledge on the subject ! Thank you for your insights !!!
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Old Aug 18, 2004, 3:17 PM   #4
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SalBolzano, thanks.

BTW I neglected to mention that flare is caused by internal reflections, better coatings can help but the more elements a lens has the greater chance of flare. The very broad range zooms used on many digicams are prime candidates for flare.

Ira
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Old Aug 18, 2004, 8:24 PM   #5
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Ira covered what it does very well.
trueno92 wrote:
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... and what environment would i NOT want to use one....
The major place not to use a petal sun shade is when the front element (filter holder) turns as you focus and/or zoom. That will put the petal into the wrong place without constant adjustment/fiddling/cursing/...
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Old Aug 18, 2004, 9:58 PM   #6
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Guys ... I suspect that they invent that petal hood to make the camera … sexier, hehe :-D
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Old Aug 19, 2004, 12:09 PM   #7
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That would be my theory KCan, I own a Pentax Optio 33L co I must have Petal hood envy!

Ira
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