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  #1  
Old 01-15-2008, 10:59 AM
Loic_bzh Loic_bzh is offline
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Default "stars effect" in night shots / "effet 彋oile" de nuit

(fran蓷is plus bas)
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Night shots with low shutter speed and small aperture offers us the famous "star effect" around the lights. But why some of them have 6 rays of light, other 8 or even 18... Here are two examples on my lasts photos:

- Canon EOS 350D + Canon EF-S 10-22mm f/3.5-4.5 USM @ f/13.0 : 6 rays stars (see the example)
- Canon EOS 350D + Sigma 70-300mm F4-5.6 APO DG Macro : 18 rays stars (see the example)

Anyone knows why? Will the same lens always draw the same stars? Does perture wideness counts?
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Le fameux "effet etoile" dans les photos de nuit longue exposition et avec une faible ouverture est connu. Mais je me demande ce qui d嶨init le nombre de "branches" de ces 彋oiles? Voici deux exemples avec mes deux denriers posts:

- Canon EOS 350D + Canon EF-S 10-22mm f/3.5-4.5 USM @ f/13.0 : 彋oiles 6 branches (voir l'exemple)
- Canon EOS 350D + Sigma 70-300mm F4-5.6 APO DG Macro : 彋oiles 18 branches (voir l'exemple)

Le m瘱e objectif donnera toujours les m瘱e 彋oiles? L'ouverture joue-t-elle un r犨e dans le nombre de branche?
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  #2  
Old 01-15-2008, 11:03 AM
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bibiweb bibiweb is offline
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Default "stars effect" in night shots / "effet 彋oile" de nuit

Salut Lo騃,
Un sujet largement couvert il n'y a pas longtemps gr歊e une photo post嶪 par JiP. Je te laisse lire l'嶰hange ce sujet ici.
;o)
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Old 01-15-2008, 11:23 AM
Davids Davids is offline
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Default Re: "stars effect"

hope this helps;
http://dptnt.com/2007/12/what-causes-the-sparkles-in-night-photos/
regards,
David
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Old 01-15-2008, 12:21 PM
Loic_bzh Loic_bzh is offline
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Default Re: "stars effect"

Thanx, Brigitte and David! :)
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  #5  
Old 01-16-2008, 05:33 PM
AdrianW AdrianW is offline
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Default Re: "stars effect" in night shots

I haven't followed the links; but usually the number of points is the same as the number of blades in the aperture.

To get nice stars without a filter you usually have to stop the lens down quite far. f16 would be a reasonably safe value; of course your images will be slightly less sharp too, as it's the same effect that causes the stars as causes a loss in sharpness when using apertures narrower than f8 (on a dSLR); diffraction.

Another interesting effect is that generally digital stars (beneath f16) diverge (spread out), whilst film tends to converge. At f16 generally they both converge.
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