Weird concentric circle pattern. 5d Mk2 Star Trails

[fokker]

Here is my photo.

Here is my problem. (1:1 crop in the centre of the frame)

Any ideas what this might be? I've never noticed it in any other photos, but this was the longest single exposure I've taken to date, at 2 hours and 400 ISO. I'm thinking that it must be some unusual noise artefact brought on by the long exposure at a moderate ISO level. I also neglected to have the in-camera long exposure noise reduction turned on for this shot, which led to a lot of 'speckles' of noise in the final shot which I had to remove in photoshop. But I'm stuck what to do on this one.

 

[Aloicious]

what lens were you using, any filters on it? the patterning of it is too organized and ordered to be noise IMO....I would think it would more likely be some kind of defect in a lens glass element (or more likely a filter) that is only manefesting itself under the extremely long exposure...I've never seen anything like it, but I really doubt it's any kind of sensor noise. that speckled noise is sensor noise, but not the circles IMO.

you could try to re-create the effect with the same exposure settings and different lenses (with and without any filters) to try and narrow down the source of the problem, but with a 2hr exposure, that would take quite a long time...

or maybe you captured some kind of rip in the fabric of the spacetime continuum happening heh j/k...

 

[fokker]

Lens used was a Sigma 28mm f/1.8 (pretty sure there was no filter on it), a pretty good lens although it suffers from lens flare fairly badly. I wonder if this is some kind of flare caused by the light of the stars? Or possibly from light coming in through the viewfinder and reflecting off the focusing screen?

 

[Tony S]

Does that show up in prints or only on a computer screen? Sometimes you get pattern like artifacts with jpegs being compressed too much that really stand out on computer screens.

 

[invisible]

(pretty sure there was no filter on it)

Those concentric circles indicate that a filter was used. There is a convoluted technical reason that explains why those artifacts appear, but the easy answer is: filters should never be used when shooting the night sky. I learned this the hard way

 

[amolitor]

That looks like a Moire pattern to me. Some sort of aliasing interaction between the finely spaced lines of the star trails and the grid nature of the sensor array. It's basic to what you're photographing, if so. Use a softer lens

Could be something else, I suppose, but that's my best guess.

 

[KmH]

Yep! I agree it's likely Moiré - Moiré pattern - Wikipedia, the free encyclopedia

But, both a clear filter or a UV filter can produce very similar concentric circles.

 

[Helen B]

It looks like an interference pattern rather than moire. As invisible says, likely to have been caused by a filter-lens front element interaction.

 

[TCampbell]

I don't think that's moire. Moire could appear anywhere in an image and this is in the center. I suspect the filter.

 

[christop]

I also vote for interference, a la Newton's Rings (Newton's rings - Wikipedia, the free encyclopedia). If there really was no filter in front of the lens, I'm thinking that it might be caused by adjacent lens elements inside the lens itself.

 

[amolitor]

Wha? Isn't Moire a form of interference pattern?

I see that it probably has nothing to do with the star trails per-se, being exactly centered in the frame. Probably something in the optical system, probably a filter as people have suggested! I'm no expert, but it makes sense to me.

 

[Garbz]

Moire patterns don't appear as perfect circle rings. More like interference between two lines. Also they only appear when there are crossing lines such as lines in the picture too small to resolve (and the anti-aliasing filter is missing from the camera) or when photographing a pattern which is slightly misaligned against the pattern of pixels on the sensor.

As others have mentioned these looks like Newton rings. They usually occur when two pieces of glass touch each other. Usual culprits are cheap filters but it can also be a sign of lens damage where two lens elements are starting to peel apart, or the anti-aliasing filter coming apart on the camera sensor. This goes doubly so for being in the very dead centre of the frame.

Check some of your other pictures. It's unlikely this has anything to do with a night exposure.

 

[Robin_Usagani]

Thats a sign from an alien. The end of our world is coming.

 

[Helen B]

You can get Newton's rings when the centre of the front element is close to the rear of the filter. You could try adding a spacer ring or rings, or tilting the filter plane slightly. Better to remove the filter, of course.

 

[invisible]

I'm going to add that the problem tends to be more visible when shooting the aurora borealis, of which there seems to be a hint on the OP's photo. For more info, see here: Aurora borealis photography - No lens filter! - Alaska Photography Blog