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04-01-2017, 06:59 PM   #1
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Strange artifacts in photo - What could cause this?

I am wondering if anyone has any thoughts on what would cause the strange artifacts in the photo below. I shot this using a K-1 and 100mm WR macro. I noticed this recently when I was deleting photos i didn't want. You can see multi-coloured dots on the in focus red berries and there are white dots with halos in the out of focus red berries. I took about 6 photos of the same shot and they were all the same. This is the only time I have seen these in my photos and haven't seen them in photos taken after this. The camera was sitting right at ground level and it was under full sun. Any feedback would be appreciated. Thanks

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04-01-2017, 07:06 PM   #2
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Its called bokeh. The reflections / specular-highlights off the berries appears to be multicolored in many areas.
When out of focus the result can be multicolored-out-of-focus spots.
04-01-2017, 07:49 PM   #3
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A guess

It could be the sun's angle (or if a flash was used) was reflecting in incoming light off the internal lens elements
04-01-2017, 09:36 PM   #4
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I believe you are seeing reflections of the light source and objects in the room. Had the berries been misted?

Edit: I just noticed what the sprig is set on. Those are prismatic reflections off the ground glass below.


Steve


Last edited by stevebrot; 04-01-2017 at 09:46 PM.
04-02-2017, 07:26 AM   #5
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First thing I noticed was this area in the crop below... (didn't get a chance to get to my desktop until now to post what I was talking about).
Either surface is oily or some sort of metamerism is reflecting multiple colors off the berries.
It isn't terribly uncommon on all sorts of things. Nylon yarn/thread can also cause some prismatic highlights, as can pet hair sometimes.

04-02-2017, 01:17 PM   #6
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The patterns in the second photo look like airy disc diffraction patterns. Maybe coincidence, but it's very eerily similar.

Could this be aperture related?
04-02-2017, 07:20 PM   #7
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Thanks everyone for your comments. I took this photo when I was out for a walk and saw the sprig as a possibly interesting contrast to the snow. The sprig was actually just sitting on surface of the snow which had slightly melted then refroze creating ice crystals on the surface. The sun was really bright at the time. It almost does look like the sprig is sitting on glass. Its possible the berries could have had some moisture/frost or natural oils on them but i never really looked that closely at the time. I have now used an air blower to lightly remove dust from the mirror box area of the camera and my lens. I will also have a close look at my lens to see if there is any contaminants on the lens glass. I had not noticed anything previously.

If this is aperture related is there any way to test this.

Thanks again your replies are appreciated.
04-02-2017, 07:57 PM   #8
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QuoteOriginally posted by silvercamp Quote
If this is aperture related is there any way to test this.
There's probably nothing wrong with the lens- I was just pointing out a phenomenon of point sources of light and small apertures.

Hopefully an optics expert chimes in here, but what I was thinking was that the specular highlights on your berries are so small that they are essentially point sources of light. At high aperture values, after diffraction kicks in, those point sources could manifest as airy discs when you defocus (as is the case in photo #2).

Some more info here: Circular Aperture Diffraction

Every lens will do this-- I'm thinking that you just found a subject with very interesting highlights (as others have mentioned) which cause the effect to show. You can test this by slowly opening up the aperture and seeing if the effect gets fainter or disappears. Your images are f/13. Try f/11, then f/9.5, f/8, etc. If it is aperture related diffraction then it should disappear rather quickly.

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