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09-26-2011, 12:24 PM   #1
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Sigma 10-20 f/3.5 long exposure reflections

All,

Attached the picture. Wondering about the "reflections" of the lights seen in the sky. What is causing them and if there is a defect in the lens.

First one is taken @f/10 for 30 seconds on K-5.

Second one is taken @f/4.5 for 4 seconds on K-5.

This is a new lens and not sure if lens has any issues.

Thanks

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09-26-2011, 12:28 PM   #2
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That's lens flare, and can be caused by the overbright light sources in your shot. Ways to reduce it include a hood (although wouldn't make much of a difference here), lens coating (dunno if the 10-20 3.5 does anything in that regard), smaller aperture (although if you're seeing it at F10....) and not shooting at overbright light sources.

With regards to the lens, hopefully someone who has experience with the lens can chime in.
09-26-2011, 12:33 PM   #3
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I get these reflections in same situations with A50/1,7, but not so often with DA lenses, so I guess it`s the coatings...
09-26-2011, 12:58 PM   #4
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Standard question: do you have filter on the lens?
That is one of main causes for upside down reflections from lights.

09-26-2011, 01:00 PM   #5
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No filters on the lens and both shots were taken in low light.
09-26-2011, 01:02 PM   #6
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Low light yes, but you had those lamps in your shot for 4 and 30 seconds, which makes them overbright compared to everything else (and so their flare in your lens elements show up due to those exposures). For example, if you shoot into the sun, you'll get those flare as well. It's dependent on the coatings on the lens.
09-26-2011, 01:09 PM   #7
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I see. That makes sense. Is it possible that the lens did not have adequate coatings?
09-26-2011, 01:12 PM   #8
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Also, I have taken couple of more shots around the same time with same shutter speed and aperture and I do not see the flare in them. The only difference is focal length.

09-26-2011, 01:14 PM   #9
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Was it into direct light? Check the photos inside the 10-20mm club on this forum to try to find similar shots. I saw that shooting into the sun gives some pretty strong flare. I don't know if your lens is lacking something or not.
09-26-2011, 02:35 PM   #10
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QuoteOriginally posted by godavari Quote
Also, I have taken couple of more shots around the same time with same shutter speed and aperture and I do not see the flare in them. The only difference is focal length.
Just guessing here, but with the change in focal length are the street lamps still in the shot? If not, that's likely why you no longer see the flare that was previously produced in the 10-20mm shots. I wouldn't suspect that your lens has any less coatings on it, I'd more suspect your technique of including the lamps. It is difficult to overcome a direct light source and not get flare (hence why you try not to shoot into the sun).
09-26-2011, 02:55 PM   #11
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Street lights are in both shots. Attached other shot.
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09-26-2011, 03:00 PM   #12
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It could be - and only guessing here - that the longer focal length reduces the available angles of light refraction hitting the lens (by reducing the FOV), and gets rid of the flare.

My guess only though.
09-27-2011, 06:26 AM   #13
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I have the f/4-5.6 version of this lens and it is generally very good at avoiding flare, particularly the kind that can wash out a photo. But it is a wide angle lens, so any direct light source is likely to cause flare spots or internal reflections. The thing is, they are about as easy to edit out as sensor dust. Why worry?
09-27-2011, 06:38 AM   #14
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I was just concerned that there is manufacturing defect and I do not need to get the replacement. As it appears that it is fairly common then I wouldn't worry about it. Thanks for all the replies.
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