Image Anomaly-What Is It and What Causes It?

LMB49

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Larry Burke
I have a Sony a6600 camera body and a Sigma 100-400 mm f5-6.3 DG DN OS Contemporary lens that I purchased for bird photography. I eventually noticed what appears to be an anomalous pattern in the background of some of my bird photos that, to my eye, ruins the image. It consists of close-together, fuzzy lines running at an angle from the top left to lower right of the image. It tends to show up in photos with a complex background such as reeds, grasses, tree leafs, sandy or pebbly beaches and similar environments. I took the a6600 and the lens, along with photo samples of the anomaly, to the dealer I bought them from. He thought that the problem was with the a6600’s sensor and recommended sending it in to Sony, which was done. Sony did a “complete repair and return to factory specs, AF test, check, recalibration and realignment.” This did not fix the problem, which is still there.

I have included some of my RAW unprocessed (but cropped) images that show the anomaly. Have any of you seen this anomaly before and know what it is? Is it the sensor or some other issue with the a6600 or a lens problem? I sure would like to know so that I can get it resolved. Thanks.
 

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Take some similar images at the same apertures with other lenses. This will tell you straight away if it's something to do with the camera.

The Sigma lens is a FF lens. Unlikely but could have something to do with it, maybe some type of weird glitch between it and the A6600...
 
The third one looks like there's a foreground green object.

The others might be something that I have seen called "double-line bokeh" (even though it can be triple line...). It's thought to be a lens artefact, not camera related, more associated with longer focal lengths. I can't give you the technical details, but if you search on that you may find more.

(hmm - some of the searches suggest it's related to image stabilisation - I hadn't seen that before, and apparently disagreement is rife!)
 
I shot one image when the bokeh looked super weird - in that case I was shooting through a net, and the net was invisible, but the effect on parts of the bokeh was horrid)
 
I like Clint's suggestion.

I have that lens but have never seen that kind of background. The shots of the Cedar Waxwings are particularly odd.

I use mine on an A7-IV and while I don't own an A6600, I do have an A6000. I can mess around and see if the same problem shows up.

There are uber crops and have all been processed. I don't think processing or not would make any difference unless you messed with blurs in the background, so they should be indicative. They were made with a 7RM3 and the Sigma 100-400. Just looking at yours, I would think the dog photo if any would exhibit the same behavior if it were the lens.

52205325943_569d6c6b94_o.jpg
  • ILCE-7RM3
  • 100-400mm F5-6.3 DG DN OS | Contemporary 020
  • 225.5 mm
  • ƒ/9
  • 1/100 sec
  • ISO 100
52204295382_ba317c8fd5_o.jpg
  • ILCE-7RM3
  • 100-400mm F5-6.3 DG DN OS | Contemporary 020
  • 313.9 mm
  • ƒ/6.3
  • 1/500 sec
  • ISO 100
52204295192_7e26dbcb19_o.jpg
  • ILCE-7RM3
  • 100-400mm F5-6.3 DG DN OS | Contemporary 020
  • 100.0 mm
  • ƒ/6.3
  • 1/500 sec
  • ISO 100
 
It's known as Nervous Bokeh, and it's one of those things that can't be helped. Often it's the wind moving things in the background, which kill any chance of a nice smooth backdrop, grass and bushes are the worst affected, or it's the way light is falling on the background. Have a google of that term, lots of ideas about it and it's causes.
 
It's known as Nervous Bokeh, and it's one of those things that can't be helped. Often it's the wind moving things in the background, which kill any chance of a nice smooth backdrop, grass and bushes are the worst affected, or it's the way light is falling on the background. Have a google of that term, lots of ideas about it and it's causes.
But Kev, haven't we seen other examples of nervous bokeh on this site with that lens? or am I imagining it?
 
Nervous bokeh is a term that can describe any kind of unwanted, busy bokeh. Soap bubble, donut, angular, etc. I don't think anyone even used the term 'bokeh' until the mid 90's. If you look at my images with the same lens, there is nothing that exhibits the same pattern as shown in the OP's post.

Of the three I posted the most 'nervous' to me is the dog. But is that bad bokeh or the background? The dog is laying in a field with blossoming white clover. I don't know how you get around that background other than processing it more in post. How much a different lens would matter in this case would be up for debate.

The bokeh in all three shots differs and is dependent on the background, the most pleasing (to me) is the sheep with the simplest and most plain background, while the drum major is in between, both in pleasant/unpleasant bokeh and the extent of a more complicated background.

The only way to tell if the lens is at fault is to do exactly what @Maskless Crusader suggested: Shoot the same scene with different lenses and view the results.

This is the most I've ever considered bokeh in my life. I typically ignore it in my photos unless it's a bird or person and I'm looking for it specifically. Having said that, the lines shown in the OP's images would absolutely bug the crap out of me.
 
But Kev, haven't we seen other examples of nervous bokeh on this site with that lens? or am I imagining it?
I think it occurs on any lens, it's not specific to a lens but more conditions. Other things that can cause this effect are shooting through double glazing, or using a filter, especially when using a very high res sensor, which picks up everything.
Take a look at Jabos Kingfisher post. Lots of this on there too
 
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