Wavy patches in bokeh

Sudhakar Ravindranath wrote:

In the photo above, when you expand and view the background, instead of a smooth bokeh effect wavy lines occur. Can anyone explain why this happens?

Camera: Nikon D5300, Lens Sigma 150-600mm Contemporary

Pucture shot at 1/2000 ISO 3200 Aperture 5.6

I have seen this same effect shooting with a Nikon 80-400mm f4.5-5.6 AF VR on a Fuji S2 dslr.

At first I thought it was down to the VR but I don't think I ever resolved what caused it.

It was always the background that had the odd effects never the subject.

Mark_A

Thread for Sunrise & Sunset pictures (part 3!)
https://www.dpreview.com/forums/post/60273364

Thank you. Yes, but photos by many of my friends have smooth bokehs. That’s what makes me wonder if it is a mismatch of camera model with lens etc.

Thanks,  I don’t think it could be heat shimmer because even in much closer subjects shot early in morning I get the same effect.

This was shot early morning. Here too, in the background where the sky is seen, the same wavy bokeh occurs.

Sudhakar Ravindranath wrote:

In the photo above, when you expand and view the background, instead of a smooth bokeh effect wavy lines occur. Can anyone explain why this happens?

Camera: Nikon D5300, Lens Sigma 150-600mm Contemporary

Pucture shot at 1/2000 ISO 3200 Aperture 5.6

This sort of question has come up before and one likely explanation is interaction between foreground and background bokeh.  If, by chance, there was a twig crossing in front of the camera and much closer than the bird, it would be so out-of-focus that it would not be visible in the picture.  However, the bokeh produced by the twig can interact with the background bokeh to produce stripes such as in your picture.

See this post for some examples.

I wouldn't think it's caused by some object between the camera and the background because it appears to cover the entire background uniformly.

My best WAG, and that's all I represent it as being, is that it is related to the VR.  3rd party mfg.'s offerings are not always 100% compatible in every respect with all the bodies out there.

• I suggest you select a different VR mode and make some photos.
• Turn VR off and make some photos.
• Select a shutter speed below 1/500 and make some photos.
• Borrow one of your friend's lenses and make some photos.
• Put your lens on a friend's body and make some photos.

I found this photo from the same lens :

(see top left corner)

the author came to the conclusion that it was caused by the Optical Stabiliser .

https://www.flickr.com/photos/24408298@N08/22621700107/in/photostream/

One of the attributes of poor bokeh is nervousness.  This could well be the issue.

That article mentions a Canon lens, so I had a look and yes the results are very similar : https://www.dpreview.com/forums/thread/4141354

Excellent advice. Will try the lens on other bodies etc and experiment.

Exactly!!! It could be VR.

Sudhakar Ravindranath wrote:

Exactly!!! It could be VR.

That is very easy for you to check:  simply turn off the VR and use a tripod instead.

Schrodingers_cat wrote:

I wouldn't think it's caused by some object between the camera and the background because it appears to cover the entire background uniformly.

This conclusion is incorrect.  Rather than try to explain why, here is a simple experiment that you can easily repeat yourself that clearly shows that the stripes can cover the whole image.

I set up the camera on a tripod with a lens at 300mm f/5.6 and in manual focus with the focus set to a much closer distance than the background, thus throwing the background well out of focus.  The result was:

Out-of-focus background

Then, without moving the camera or changing the focus, I took the next shot while holding several narrow strips of black paper in front of the lens:

Out-of-focus background while strips of black paper are held horizontally across the front of the lens.  (The number of strips of paper was far less than the number of stripes visible in the image.)

Finally, I repeated the same shot, but this time with the strips of paper held at an angle to the horizontal:

Out-of-focus background while strips of black paper are held at an angle across the front of the lens.  The stripes in the image are at the same angle as the strips of paper.

If the same shot was repeated with a uniform background (e.g. uniform blue sky), then the shot is entirely uniform in colour with no stripes.  This shows that the stripes are due to an interaction between the background bokeh and the strips of paper held close to the lens.

You should be able to repeat this experiment with any lens with a large aperture, by which I mean the aperture or entrance pupil in mm (got by dividing the focal length by the f-number).  The strips of paper (or any similar objects) which you put in front of the lens must be considerably narrower than the lens aperture in mm.  The background needs to have a lot of detail in it so the bokeh is quite complicated.

Tom Axford wrote:

Schrodingers_cat wrote:

I wouldn't think it's caused by some object between the camera and the background because it appears to cover the entire background uniformly.

This conclusion is incorrect. Rather than try to explain why, here is a simple experiment that you can easily repeat yourself that clearly shows that the stripes can cover the whole image.

I set up the camera on a tripod with a lens at 300mm f/5.6 and in manual focus with the focus set to a much closer distance than the background, thus throwing the background well out of focus. The result was:

Out-of-focus background

Then, without moving the camera or changing the focus, I took the next shot while holding several narrow strips of black paper in front of the lens:

Out-of-focus background while strips of black paper are held horizontally across the front of the lens. (The number of strips of paper was far less than the number of stripes visible in the image.)

Finally, I repeated the same shot, but this time with the strips of paper held at an angle to the horizontal:

Out-of-focus background while strips of black paper are held at an angle across the front of the lens. The stripes in the image are at the same angle as the strips of paper.

If the same shot was repeated with a uniform background (e.g. uniform blue sky), then the shot is entirely uniform in colour with no stripes. This shows that the stripes are due to an interaction between the background bokeh and the strips of paper held close to the lens.

You should be able to repeat this experiment with any lens with a large aperture, by which I mean the aperture or entrance pupil in mm (got by dividing the focal length by the f-number). The strips of paper (or any similar objects) which you put in front of the lens must be considerably narrower than the lens aperture in mm. The background needs to have a lot of detail in it so the bokeh is quite complicated.

Excellent and well documented experiment. Thanx for posting.

Based on the data provided, I think I will vote for your theory rather than my theory

Perhaps the OP will get back to us with the results of his testing.

Schrodingers_cat wrote:

Tom Axford wrote:

Schrodingers_cat wrote:

I wouldn't think it's caused by some object between the camera and the background because it appears to cover the entire background uniformly.

This conclusion is incorrect. Rather than try to explain why, here is a simple experiment that you can easily repeat yourself that clearly shows that the stripes can cover the whole image.

I set up the camera on a tripod with a lens at 300mm f/5.6 and in manual focus with the focus set to a much closer distance than the background, thus throwing the background well out of focus. The result was:

Out-of-focus background

Then, without moving the camera or changing the focus, I took the next shot while holding several narrow strips of black paper in front of the lens:

Out-of-focus background while strips of black paper are held horizontally across the front of the lens. (The number of strips of paper was far less than the number of stripes visible in the image.)

Finally, I repeated the same shot, but this time with the strips of paper held at an angle to the horizontal:

Out-of-focus background while strips of black paper are held at an angle across the front of the lens. The stripes in the image are at the same angle as the strips of paper.

If the same shot was repeated with a uniform background (e.g. uniform blue sky), then the shot is entirely uniform in colour with no stripes. This shows that the stripes are due to an interaction between the background bokeh and the strips of paper held close to the lens.

You should be able to repeat this experiment with any lens with a large aperture, by which I mean the aperture or entrance pupil in mm (got by dividing the focal length by the f-number). The strips of paper (or any similar objects) which you put in front of the lens must be considerably narrower than the lens aperture in mm. The background needs to have a lot of detail in it so the bokeh is quite complicated.

Excellent and well documented experiment. Thanx for posting.

Based on the data provided, I think I will vote for your theory rather than my theory

Perhaps the OP will get back to us with the results of his testing.

or maybe you could look at previous threads on the subject , including the one on the Canon lenses that I posted above.