Seeking advice on the round circles in the middle of the photos


kiattan

New Member
Jun 1, 2013
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Singapore
#1
Recently I went to Iceland and managed to capture northern lights. I realised that some/most photos having uniform round circles in the middle of the photos.
Anyone knows what causes it?

https://goo.gl/photos/4PzkGWyWWEDNy6sr6

I am using canon 550d and tamron 17-55 lens.
 

shierwin

Senior Member
Dec 29, 2008
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East Coast
#2
Are these white dots in the same position in most of the images? May be stars:) Let hear the views of the experts here
 

SkyStrike

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Nov 29, 2010
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#3
bro, if I'm not wrong, that happens is because it's out of focus....
 

kiattan

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Jun 1, 2013
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#4
It seems to happen on the same spot for my photos. I used manual focus.

I don't see such circles for the photos taken in the day.
 

kandinsky

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Apr 26, 2008
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#5
First thought is that those look like overexposed stars? What was the exposure time?
 

shierwin

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Dec 29, 2008
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#7
It seems to happen on the same spot for my photos. I used manual focus.

I don't see such circles for the photos taken in the day.
First thought is that those look like overexposed stars? What was the exposure time?
25 or 30 seconds.
These replies explain clearly the occurrence of "white circles" :)
 

SkyStrike

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#8
It seems to happen on the same spot for my photos. I used manual focus.

I don't see such circles for the photos taken in the day.
***Not sure if your question is about OOF or not... sry if I misinterpret ur question.

Since you mentioned manual focus, I suspect that there might be some form of mis-focus (especially during night where focusing becomes tough under such situation and 10x magnification isn't usable). From my past shoot, so long if I misfocus abit, those stars will turn round (OOF). If those at the edges or other parts of the lens is not rounded, then the lens element is probably shifted/tilted internally where it causes focus to be different.
 

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kiattan

New Member
Jun 1, 2013
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#9
The circles always centered in the center of the photos. Hence I am skeptical about mis focus? Maybe I am wrong too. Quite a newbie in photography.

Later I can post more photos to better illustrate my points. Thanks all for the reply so far
 

#11
I saw the rings. Very faint rings in the middle of the photos. Only when you zoom in all the way in the center of the photos.
Quite weird. Never saw anything like this before.

Have you took the northern lights with other lens?
 

kandinsky

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Apr 26, 2008
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#12
More photos. All with rings of circles in the center. Need to zoom in into the center to see it. Regardless portrait or landscape.
https://goo.gl/photos/4PzkGWyWWEDNy6sr6
https://goo.gl/photos/xDQx1Wd7e457ig5T7
https://goo.gl/photos/7xHvzF4Hff2NmHJ18
OH! I get what you're referring to now... you're not referring to the blown out circle dots but something else.

Here's a screenshot for those who haven't noticed it yet.



-------------

Did you have a UV filter on? Found a pretty cheem explanation:

With my Nikon lenses I have found that long exposures result in concentric circles showing up in the center of the images when I use a filter of any kind. Nikon says this is due to the high reflectivity of the aurora.

Thanks to the University of Alaska forecaster, Chuck Deehr, the explanation follows. "These are interference fringes due to the parallel faces of the filter and to the narrow spectral emission at 5577 Angstroms in the aurora. That green, atomic oxygen emission line is the strongest emission in the aurora near our film and eye peak sensitivity, so it shows up first when there is any device in the optical path which sorts out the spectral emissions." So, don't use filters!

http://www.eaglestation.com/dick/aurora.html
When I looked closely at the center of the pictures (at least in the original unscaled versions), I could see concentric rings. When I first saw them, I found them to be quite strange, but interesting nevertheless.

At first, I thought they were Airy rings, but after thinking for a while, I realized that there is no small aperture from which they could arise. After some more thought, I found the solution - they are interference rings from somewhere in the optics. My suspicion fell on the UV filter I bought for my lens, a suspicion which was confirmed once I photographed another aurora without the filter.

So, where does this interference pattern come from, and what can we learn from it?

The first thing to note, is that the fact that there is an interference pattern, implies that the light is monochromatic, or at least coming from a very narrow wave band. Since I can count at least 30 rings, the waveband should be no more than about 1/30 of the wavelength. Since green is about 5500Å, the emitted waveband has to be narrower than about 200Å. In fact, the radiation is monochromatic. It comes from a well known 5577Å forbidden line of Oxygen, namely, under lab conditions, they cannot be observed.

http://www.sciencebits.com/auroras
 

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kiattan

New Member
Jun 1, 2013
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Singapore
#13
Wow. Thanks for the explanation. I tried googling but can't get any answers.

The explanation is indeed chim. And yes! I am using UV filter. It's so sad!! Chance upon northern lights and the photos turned out with the rings of circles :(


OH! I get what you're referring to now... you're not referring to the blown out circle dots but something else.

Here's a screenshot for those who haven't noticed it yet.



-------------

Did you have a UV filter on? Found a pretty cheem explanation:
 

DSolZ

New Member
Mar 6, 2010
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#14
Good information. Will take off UV filter if I ever go see northern light!
 

DSolZ

New Member
Mar 6, 2010
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#15
One question. Does the northern light look that saturated as in the photo in real life or is the photo processed to increase saturation.
 

kiattan

New Member
Jun 1, 2013
14
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0
Singapore
#16
The photos that I have posted have not been processed. I captured in jpeg and raw. The photos uploaded to Google is jpeg.



One question. Does the northern light look that saturated as in the photo in real life or is the photo processed to increase saturation.
 

Sep 27, 2015
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#20
Nice shots nevertheless bro!

One day you'll look back and know how this experience has helped to improve your photography in some way. hahaha. Everyone learns from their past mistakes.

Hope I get some luck to see them in the future :p
 

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