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Marianne Oelund, who is/was one of resident lens gurus of the Dpreview Nikon forum said this about it:

 

It's called doubling and it's normal.

Unless the lens is intentionally designed with some under-correction of SA (spherical aberration), high-contrast lines in backgrounds will provoke this kind of detail.  It is because the edges of the blur circles are abrupt, instead of diffuse.

It is difficult to maintain a pleasing background blur across the focal range of zoom lenses, and this aspect of design usually has a low priority for telephoto zooms.

 

And in a different post she explained the term for it:

It's "nisen bokeh." In Japanese, "ni" = two; "sen" = line. Double-line bokeh.  No capitalization needed.

 

Except of course it isn't normal if it disappears when the filter is removed. Or the pattern changes direction if the filter is rotated.

So the filter is causing it or exaggerating it in certain cases.

My theory at the moment is that the filter interferes with the solution the lens designers have come up with to reduce that normal nisen bokeh.

Now why? And is it just a certain sort of filter? We assume it's because it's a bad filter. But what if it is because it's a good filter?

 

First of all, putting a piece of glass or a lens in the optical path does alter the focus point slightly. So that could be it. Just a simple focus problem.

It could be that UV light has something to do with it. A bit like CA, but now with UV in stead of blue and red. Again basically a focus problem.

Both documented problems. However those two still do not explain the directional thing and that it changes with rotation.

 

I should read up on what a UV filter actually does and how it's achieved in the various types. What makes a UV filter cheap and what makes it expensive?

 

So here are some of the resources I have been reading/revisiting in the course of this:

 

Paul van Walree:

https://web.archive.org/web/20070823003700/http://www.vanwalree.com/optics/bokeh.html

https://web.archive.org/web/20120118221937/http://toothwalker.org/optics/spherical.html

 

Klaus Shuler:

http://www.bokehtests.com/styled/index.html

He thinks/explains it's caused by IS/VR: http://www.bokehtests.com/page2/index.html

So like always when a problem is difficult to understand or explain, there may be different things that cause it. Maybe even at the same time.

 

Dave Etchells: it's aspheric lenses.

 

Roger Cicala: one of many good articles: https://www.lensrentals.com/blog/2010/10/the-seven-deadly-aberrations/

And on using or not using protective filters: https://www.lensrentals.com/blog/2016/12/front-element-lens-protection-revisited/

And here again on filters with some images that show the problem with cheap filters https://www.lensrentals.com/blog/2017/05/yet-another-post-about-my-issues-with-uv-filters/

Which seems to answer my question if it could be that a good filter is causing the problems. At least it shows a bad filter causing problems that may lead to the dreaded nisen bokeh.

 

wim

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28 minutes ago, wiskerke said:

Marianne Oelund, who is/was one of resident lens gurus of the Dpreview Nikon forum said this about it:

 

It's called doubling and it's normal.


 

 

Klaus Shuler:

http://www.bokehtests.com/styled/index.html

He thinks/explains it's caused by IS/VR: http://www.bokehtests.com/page2/index.html

So like always when a problem is difficult to understand or explain, there may be different things that cause it. Maybe even at the same time.

 

 

Roger Cicala: one of many good articles: https://www.lensrentals.com/blog/2010/10/the-seven-deadly-aberrations/

And on using or not using protective filters: https://www.lensrentals.com/blog/2016/12/front-element-lens-protection-revisited/

And here again on filters with some images that show the problem with cheap filters https://www.lensrentals.com/blog/2017/05/yet-another-post-about-my-issues-with-uv-filters/

Which seems to answer my question if it could be that a good filter is causing the problems. At least it shows a bad filter causing problems that may lead to the dreaded nisen bokeh.

 

wim

 

Thanks for all that win. I haven’t read all yet. The Lens Rentals articles are great and written by someone who clearly knows what he is talking about. The idea that the lens cap itself can cause damage to the front element or filter coating, particularly in larger filter sizes, is very interesting. I reckon I have had that happen once or twice  
 

The IS/VR theory can be immediately binned as a single cause in itself as Shearwater has clearly demonstrated that the effect happens on non-VR lenses and disappeared when the first filter was removed. 

 

 

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3 minutes ago, MDM said:

 

Thanks for all that win. I haven’t read all yet. The Lens Rentals articles are great and written by someone who clearly knows what he is talking about. The idea that the lens cap itself can cause damage to the front element or filter coating, particularly in larger filter sizes, is very interesting. I reckon I have had that happen once or twice  
 

The IS/VR theory can be immediately binned as a single cause in itself as Shearwater has clearly demonstrated that the effect happens on non-VR lenses. 

 

 

 

Not so fast, IS/VR may cause some of it as well.

 

It occurred to me that a particular problem with the filters causing circular marks on the front lens (and I assume on the back of the filter as well) is that these are large diameter filters. Which may be made for wide angle lenses, and usually sold as slim filters. Some of these come (at least used to come) with a caveat: be careful that your front lenses don't protrude too much.

 

wim

 

 

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2 minutes ago, wiskerke said:

 

Not so fast, IS/VR may cause some of it as well.

 

 

wim

 

 


OK.  I actually didn’t read that link yet. I was using the basic logical principle that if a hypothesis can be proved wrong in one case, then that disproves the hypothesis but yes there may well be multiple causes for this effect (and I did qualify what I said with single cause). 😀

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3 hours ago, MDM said:


OK.  I actually didn’t read that link yet. I was using the basic logical principle that if a hypothesis can be proved wrong in one case, then that disproves the hypothesis but yes there may well be multiple causes for this effect (and I did qualify what I said with single cause). 😀

 

Yes Ockham's razor and all that.

 

wim

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On 13/08/2020 at 03:21, MDM said:


Depending on the volcano and the type of activity, you might need more than a protective lens filter. 

 

Nicaraguan volcanos tend to be more decorative than dangerous, but do put out lots of dust and sulfurous fumes.

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Looking thorough the various images of the phenomenum, it appears that the seperation between the finges gets wider the further in front or behind of the point of focus the area of the image is. As the point of focus the fringe spacing becomes so small it disappears. Long focal length mirror lens bokeh (and other lenses) show the same effect as shown admirably here. https://c1.staticflickr.com/5/4077/5394380056_55d1a78863_b.jpg

 

It suggests there's some non-uniformity in some filters (micro-waviness in the polishing or coating, or maybe the UV filtering bit is a polymer laminate with oriented polymer chain molecules)? Polarisers often have a sandwiched plastic film inside. No idea about UV filters.

 

Mark

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One thing strikes me about this effect, as someone who wears sunglasses a lot (I’m on meds that make me more susceptible to cataracts) the artefacts seen here seem vaguely reminiscent of some of the patterns you occasionally see on tempered glass when looking through polarised lenses. The fact that rotating the filter can influence the impact would seem to indicate that some sort of polarisation effect could be at play. I haven’t had chance to read any of the linked articles or research the issue in any way shape or form but it may be a possibility (or maybe not) 🤔

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2 hours ago, wiskerke said:

 

Yes Ockham's razor and all that.

 

wim


Having had a look at the Klaus Shuler bokeh site, I think I will continue my unwritten philosophy of concentrating on the subject and not worry too much about the bokeh. That guy is obsessed by bokeh. 
 

 

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2 hours ago, MizBrown said:

Nicaraguan volcanos tend to be more decorative than dangerous, but do put out lots of dust and sulfurous fumes


That is what I meant 😀. Sulfurous fumes are not good for the lungs and nor is the ash or secondary dust. 

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13 minutes ago, MDM said:


That is what I meant 😀. Sulfurous fumes are not good for the lungs and nor is the ash or secondary dust. 

And how do you make it to screw a lens protective filter in your face mask to avoid them?? Can't figure it out! 😁

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All I can say is, the filter that the retailer send me for free with my lens was this:
Green.L UV Series 77mm dHD Digital RoHS standards
You can read in the filter box: Reduce brillant light scaterring. More brillant, less flare
They forget to add: "bokeh fantasy lines included" 🙄
Price in Chinese pages: around 6€

 

The good filter I bought, put on the lens and have never take it apart since then (2014) is:
B+W XS-PRO NANO MRC UV-HAZE 77mm (ref. 1066125)
I think one of the best filters I could find/afford for that lens.
Price: between 50-90€ (it cost me 70€)

 

The lens was a brand new AF-S Nikkor 300mm f/4D IF-ED.
I used it, as most of the time, with a Kenko Teleplus Pro 300 AF 1.4X DGX, and a Nikon D90…so effective focal length is 630mm aprox.

 

With the cheap filter, used a couple of days waiting for the good one, many images show the lines. They appeared in out of focus areas, especially with variated patterns (branches, leaves, moving water surface…). The lines are most prominent in the background, and less in the foreground. Plain backgrounds like blue or gold skies doesn’t show any lines. 

 

With the expensive, and IMHO very good filter, no lines nor other side effects, in all kind of situations.

Haven’t used the lens without filter. Maybe i would find it is better without it! ;)

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14 minutes ago, shearwater said:

And how do you make it to screw a lens protective filter in your face mask to avoid them?? Can't figure it out! 😁

 

It was my understated sense of humour. I meant a respirator. I have been around a few active volcanoes in my previous life as a geologist. Some are very benign and some are very dangerous. 

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39 minutes ago, MDM said:


That is what I meant 😀. Sulfurous fumes are not good for the lungs and nor is the ash or secondary dust. 

 

Masaya Volcano has a ten minute maximum stay per car or truck and requires that vehicles be backed into the spaces so if the volcano acts up, the visitors can get out fast.  It's a regional park volcano occasionally dumps rocks -- one landed on the roof of a tourist's rental car.

 

I have photographed Momotombo after it went active for the first time since the early 20th Century, but from a distance.

 

 

 

 

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10 minutes ago, MizBrown said:

 

Masaya Volcano has a ten minute maximum stay per car or truck and requires that vehicles be backed into the spaces so if the volcano acts up, the visitors can get out fast.  It's a regional park volcano occasionally dumps rocks -- one landed on the roof of a tourist's rental car.

 

I have photographed Momotombo after it went active for the first time since the early 20th Century, but from a distance.
 

 

 

Sounds fascinating if dangerous. The explosive ones are the most dangerous and can be unpredictable as we saw in New Zealand last year. I've been to Chile but never to Central America. Maybe one day. So many amazing places 

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2 minutes ago, MDM said:

 

Sounds fascinating if dangerous. The explosive ones are the most dangerous and can be unpredictable as we saw in New Zealand last year. I've been to Chile but never to Central America. Maybe one day. So many amazing places 

 

I met a Swedish family on one flight back to the US who came to Nicaragua every December and who always visited Volcan Masaya.  People can drive up to overlook Santiago Crater.  Costa Rica and Guatamela also have volcano tourism, not sure who lets the tourists drive up the closest to active volcanos.

 

Momotomobo is near Leon (it destroyed Leon Viejo).  Best viewing is from Puerto Momotombo on Lake Managua.   This is with the 200mm end of a Sony 55-200mm lens for their APSC cameras.   From Puerto Momotombo at dusk.  peak-of-volcan-momotombo-showing-recent-

 

 

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15 hours ago, wiskerke said:

Marianne Oelund, who is/was one of resident lens gurus of the Dpreview Nikon forum said this about it:

 

It's called doubling and it's normal.

Unless the lens is intentionally designed with some under-correction of SA (spherical aberration), high-contrast lines in backgrounds will provoke this kind of detail.  It is because the edges of the blur circles are abrupt, instead of diffuse.

It is difficult to maintain a pleasing background blur across the focal range of zoom lenses, and this aspect of design usually has a low priority for telephoto zooms.

 

And in a different post she explained the term for it:

It's "nisen bokeh." In Japanese, "ni" = two; "sen" = line. Double-line bokeh.  No capitalization needed.

 

Except of course it isn't normal if it disappears when the filter is removed. Or the pattern changes direction if the filter is rotated.

So the filter is causing it or exaggerating it in certain cases.

My theory at the moment is that the filter interferes with the solution the lens designers have come up with to reduce that normal nisen bokeh.

Now why? And is it just a certain sort of filter? We assume it's because it's a bad filter. But what if it is because it's a good filter?

 

First of all, putting a piece of glass or a lens in the optical path does alter the focus point slightly. So that could be it. Just a simple focus problem.

It could be that UV light has something to do with it. A bit like CA, but now with UV in stead of blue and red. Again basically a focus problem.

Both documented problems. However those two still do not explain the directional thing and that it changes with rotation.

 

I should read up on what a UV filter actually does and how it's achieved in the various types. What makes a UV filter cheap and what makes it expensive?

 

So here are some of the resources I have been reading/revisiting in the course of this:

 

Paul van Walree:

https://web.archive.org/web/20070823003700/http://www.vanwalree.com/optics/bokeh.html

https://web.archive.org/web/20120118221937/http://toothwalker.org/optics/spherical.html

 

Klaus Shuler:

http://www.bokehtests.com/styled/index.html

He thinks/explains it's caused by IS/VR: http://www.bokehtests.com/page2/index.html

So like always when a problem is difficult to understand or explain, there may be different things that cause it. Maybe even at the same time.

 

Dave Etchells: it's aspheric lenses.

 

Roger Cicala: one of many good articles: https://www.lensrentals.com/blog/2010/10/the-seven-deadly-aberrations/

And on using or not using protective filters: https://www.lensrentals.com/blog/2016/12/front-element-lens-protection-revisited/

And here again on filters with some images that show the problem with cheap filters https://www.lensrentals.com/blog/2017/05/yet-another-post-about-my-issues-with-uv-filters/

Which seems to answer my question if it could be that a good filter is causing the problems. At least it shows a bad filter causing problems that may lead to the dreaded nisen bokeh.

 

wim

 

This is very interesting Wim. I think your suggestion of a UV filter possibly creating a problem similar to CA sounds quite plausible. It's good to have a name for it now. I looked up info on nisen bokeh and found another clear example of it involving a UV filter on a telephoto lens: https://www.flickr.com/photos/peterschoen/5683825633

 

The photographer mentions he was using a mid-range multi-coated Kenko filter (this would be the same with my Kenko filter). I doubt the brand is the issue though, but particular filters in general when used on telephoto lenses. Cheap, mid-range and expensive filters may all have different characteristics.

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8 hours ago, shearwater said:

All I can say is, the filter that the retailer send me for free with my lens was this:
Green.L UV Series 77mm dHD Digital RoHS standards
You can read in the filter box: Reduce brillant light scaterring. More brillant, less flare
They forget to add: "bokeh fantasy lines included" 🙄
Price in Chinese pages: around 6€

 

The good filter I bought, put on the lens and have never take it apart since then (2014) is:
B+W XS-PRO NANO MRC UV-HAZE 77mm (ref. 1066125)
I think one of the best filters I could find/afford for that lens.
Price: between 50-90€ (it cost me 70€)

 

The lens was a brand new AF-S Nikkor 300mm f/4D IF-ED.
I used it, as most of the time, with a Kenko Teleplus Pro 300 AF 1.4X DGX, and a Nikon D90…so effective focal length is 630mm aprox.

 

With the cheap filter, used a couple of days waiting for the good one, many images show the lines. They appeared in out of focus areas, especially with variated patterns (branches, leaves, moving water surface…). The lines are most prominent in the background, and less in the foreground. Plain backgrounds like blue or gold skies doesn’t show any lines. 

 

With the expensive, and IMHO very good filter, no lines nor other side effects, in all kind of situations.

Haven’t used the lens without filter. Maybe i would find it is better without it! ;)

 

That's very interesting Shearwater and good to know. In your case, the higher quality filter seems to eliminate the problem. I think I will go without a filter on my telephoto lens for a while and rely on the hood to protect it. If I do ever get another UV filter in the future, I'll keep in mind the B+W one you mention there. I'm very much looking forward to taking wildlife images without the annoying lines from now on 🙂

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9 hours ago, MDM said:

 

It was my understated sense of humour. I meant a respirator. I have been around a few active volcanoes in my previous life as a geologist. Some are very benign and some are very dangerous. 

Yes, I understood. I only was trying to make a (bad) joke...but english is not my mother tonge...and spanish humor is different, and writing is less expresive...so it could sounds rude. Far away from my intentions. Sorry about that.

Never been near an active volcano...it sounds to be a heartbeating experience 😲

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1 hour ago, Sally R said:

 

That's very interesting Shearwater and good to know. In your case, the higher quality filter seems to eliminate the problem. I think I will go without a filter on my telephoto lens for a while and rely on the hood to protect it. If I do ever get another UV filter in the future, I'll keep in mind the B+W one you mention there. I'm very much looking forward to taking wildlife images without the annoying lines from now on 🙂

 

B+W, is a very reputade german brand. One of the best filters you can get. Quality and pricy. I have no shares of them ;)

I do also use Hoya filters, the pro series (they have many different qualities). Good price-quality ratio.

Great to know that you will get rid of the annoying lines. Enjoy it! :)

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17 minutes ago, shearwater said:

Yes, I understood. I only was trying to make a (bad) joke...but english is not my mother tonge...and spanish humor is different, and writing is less expresive...so it could sounds rude. Far away from my intentions. Sorry about that.

Never been near an active volcano...it sounds to be a heartbeating experience 😲

 

 

No pass nada hombre. 😀

I didn’t take your comment in any strange way at all. It can be hard enough to communicate in one’s native language on forums never mind in a second language. 
 

And if you have been to El Hierro and La Palma you have not just been near but effectively on active volcanoes. El Hierro is a series of very young volcanoes and could erupt in any one of several places including underwater. The whole of southern La Palma (Cumbre Viejo) is essentially a giant active stratovolcano. Similarly with Tenerife. The last eruption on La Palma in 1971 formed the Teneguia cone in the far south. Many people don’t realise what they are walking or living on. Fortunately they have extensive monitoring systems in place to warn of impending eruptions. 

 

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1 minute ago, MDM said:

 

 

No pass nada hombre. 😀

I didn’t take your comment in any strange way at all. It can be hard enough to communicate in one’s native language on forums never mind in a second language. 
 

And if you have been to El Hierro and La Palma you have not just been near but effectively on active volcanoes. El Hierro is a series of very young volcanoes and could erupt in any one of several places including underwater. The whole of southern La Palma (Cumbre Viejo) is essentially a giant active stratovolcano. Similarly with Tenerife. The last eruption was on La Palma 1971 formed the Teneguia cone in the far south. Many people don’t realise what they are walking or living on. Fortunately they have extensive monitoring systems in place to warn of impending eruptions. 

 

Thanks, MDM :)

Yes, you are completely right. El Hierro and La Palma are two "floating", and by now asleep, volcanoes in the Atlantic sea. I really meant an active in the moment volcano.  Actually, as you mentioned, there was an underwater eruption near the south cape of El Hierro in october 2011. Diving tourism dissapeared. I went there one year later (nov2012) and as far as I was told the underwater life hadn't recovered completely at that time. Nor even diving tourism. Don't think it has fully recover.

I remember a volcanoes documentary taking about a possible future eruption in west La Palma, that could badly destroy east coast of America by its provoked tsunami. Terrifying.

 

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9 minutes ago, shearwater said:

Thanks, MDM :)

Yes, you are completely right. El Hierro and La Palma are two "floating", and by now asleep, volcanoes in the Atlantic sea. I really meant an active in the moment volcano.  Actually, as you mentioned, there was an underwater eruption near the south cape of El Hierro in october 2011. Diving tourism dissapeared. I went there one year later (nov2012) and as far as I was told the underwater life hadn't recovered completely at that time. Nor even diving tourism. Don't think it has fully recover.

I remember a volcanoes documentary taking about a possible future eruption in west La Palma, that could badly destroy east coast of America by its provoked tsunami. Terrifying.

 

 

Yes it shows how important exact language can be. If you ever want to see an erupting volcano then pay a visit to Stromboli, one of the Aeolian Islands in the Mediterranean north of Sicily. 

 

I know the documentary you are talking about. It was way too sensationalist and caused a lot of unnecessary fear. The BBC should be ashamed of itself for that one. The idea that the Cumbre Viejo of La Palma is on the verge of collapse is vastly exaggerated. The evidence used has been strongly refuted since the documentary was made in fact. That said, mega-collapses of volcanoes can and do happen but are very very rare.

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On nisen bokeh, Roger Cicala (of LensRentals) four years ago said this, and I tend to agree by now, even without having seen the why of the effect caused by some filters:

 

Cicala:
Dec 12, 2016
https://www.dpreview.com/forums/thread/4090070?page=2

 

One thing I would like to point out is we tend to over-generalize in this type of discussion somewhat. Nisen Bokeh can have a lot of causes.

Some are correctible: bad filter, a bit of oily film on the lens, etc.

Some are inherent to lens design: such as lenses with overcorrected spherical aberration, etc.

Some are for a bad copy of the lens with a decentered or tilted element.

Often it will only affect foreground or background bokeh.

The IS unit is a lens element and in certain positions could play a role, at least in theory. This will often be very random, only if the IS unit is in a certain (usually maximum correcting) position which will vary shot to shot or even among some of several shots in a burst.

Focusing distance also plays a role, with it being more apparent at some distances than others.

With ANY zoom lens, however awesome the zoom is, there will be certain focal lengths at which it is more likely appear or be more noticeable than other distances. And, of course, now we have the dual feature of focusing distance and zoom focal length coming into play.

So it isn't surprising to me that we see it in some shots and not others. If I had a lens that others all raved about showing Nisen bokeh, I'd be concerned something was wrong. If I sometimes saw it, and others sometimes saw it, I'd be trying to narrow down the conditions in which it occurred so I could avoid them when possible. Although that's a lot of work to do, so knowing myself I'd probably just accept the randomness of it.

 

 

Then there is this image of a (probably cheap) UV filter:

UV filters test - supplement - Introduction

translated https://www.lenstip.com/120.1-article-UV_filters_test_-_supplement_Introduction.html

from a well known Polish photography site https://www.optyczne.pl/

 

It's been disputed what we're seeing here, but whatever it is, it's totally not even:

  From https://www.lensrentals.com/blog/2017/06/the-comprehensive-ranking-of-the-major-uv-filters-on-the-market/

  Brandon Dube - Chris Jankowski 3 years ago

  In the second link (120...) they claim they've captured interference fringes. They most assuredly have not -- there is no type of interferometer (Fizeau, white light, michelson, lateral shearing, etc) that produces such sharp fringes with that large of a spacing.

  Their spectral transmission charts are difficult to comprehend, as is their notation for extinction coefficient. IMO.

 

wim

 

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