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09-14-2013, 12:31 AM   #1
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night scene: round lights become star shape

I has K-r and kit lens. This picture was taken at F22, 8 secs.

Is it because the aperture too small and all round shape lights turn to star shape? Or it is the quality of the lens?

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09-14-2013, 12:54 AM   #2
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I think it's the light diffracting on each blade, you have ix blades, and each one distorts the light at small apertures, making the pattern you see above. So yeah, it's the small aperture.

Certain lenses, like the DA15mm Ltd are renowned for their 'starbursts' so they aren't a sign of a bad lens at all, but generally having an uneven number of blades means you get more of these lines, making them look prettier.
09-14-2013, 02:27 AM   #3
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09-14-2013, 03:09 AM - 1 Like   #4
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You get 2 spikes per blade. But when the number of blades is even, the spikes overlap and appear as a single spike. Odd blade numbers tend to produce sharper spikes because of this.
So on a lens with 6 blades you get 6 spikes
with 7 blades, 14 spikes
8 blades 8 spikes
9 blades 18 spikes.
You can get starbursts from about f5.6 onwards, but you need a bright light source relative to the rest of the picture. The DA15 and DA21 tend to produce the best starbursts I've seen and will do them in daylight off any shiny surface.

09-14-2013, 07:45 AM   #5
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The DA15mm is actually prized because of the quality of it's starburst effect, and certainly you wouldn't call that a poor lens! One more note, if there is a little bit of mist or fog in the air, the starburst will not happen. It has to be pretty clear. Also, if you open up the aperture, there will be no starbursts.

Clear Day:



Foggy Night:

09-14-2013, 10:58 AM   #6
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Thanks for the replies.

Does that mean I can't get the round shape lights? Would open up the aperture help?
09-14-2013, 01:49 PM   #7
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Yes, if you look at the examples in the link, the more you stop down - the more the star effect. The more you open up the lens, the more you diminish the effect.

09-14-2013, 02:15 PM   #8
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You c an also get round effects with preset lenses because they usually maintain a perfect circle shape as they stop down

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