I sometimes come across such a phenomenon when the circles of confusion in the pictures have strange artifacts - dots, specks, lines, grooves, concentric rings, etc. Sometimes this mud in the bokeh is very annoying. But, in fact, why is it happening? In this article I will give an example and describe my findings.
Dirt on the bokeh
For the experiment, I used the lens Industar-50-2 3,5 / 50that I’m not sorry to torment. The shooting took place using a camera Nikon D80, I shot the Christmas garland in a defocused state (the lens was focused on MDF).
The first picture already has a characteristic canvas in the form of a strip and small spots on the circles of blur. I want to note that dirt on the side has nothing to do with sensor cleanliness. By the way, my camera Nikon D80 recently was in the service of cleaning the matrix. If the dirt were on the sensor, then it would appear not only in circles of blur, but also in any other parts of the pictures and always in the same place. In the case of mud on the side, one can observe the repeatability of the mud pattern in different parts of the frame.
Canvas. Best seen on the green circle on the right. Canvas is repeated in all circles of confusion.
The picture below was taken after carefully wiping the front and rear lenses of the lens with a special cloth with microfiber to care for the optics. The circles in the blur zone became almost completely clean.
After wiping the lenses
To see how real dirt affects the lenses, I sprayed Industar-50-2 3,5 / 50 rear lens with monitor cleaning fluid:
Monitor back lens splashed with monitor cleaner
After that, the nature of the dirt on the bokeh has changed:
With splattered back lens
Please note that when the lens is very dirty, a repeating pattern of dirt is clearly visible on the circles of blur. And another shot with stronger splashes:
Splashing bokeh
For the sake of interest, I completely filled the back lens with cleaning fluid, it turned out something very funny:
With fully flooded rear lens
On the rear lens of Industar-50-2 3,5 / 50, I glued the letter 'a', imitating a large speck of dust :).
The letter 'a' from the kit for children is glued to the rear lens of the lens
Bokeh has become like this:
Bokeh with a letter on the back of the lens
By the way, the letter 'a' is actually a kind of diaphragm located behind the rear lens. If this letter is placed on the front lens, then we get the effect 'homemade bokeh'.
The letter 'a' from the kit for children is glued to the front lens of the objective
Here's what happened:
The letter on the front lens
Then I wanted to scratch the lenses of the lens, but my conscience did not allow me, because I just covered the rear lens with kitchen salt, simulating a lot of dust :)
The back lens is covered with kitchen salt
With such a strong pollution, the following dirt turned out on the side:
Heavy mud
After that, I seemed to wipe the rear lens away from the salt qualitatively, but after the test shot it turned out that my efforts were not crowned with complete success, I left dirt at the edges of the lens, which then became very visible in the pictures:
A speck of poor rubbing of the rear lens from salt
Results
- Dirt on the bokeh (on circles of blur) in the first place connected with real dirtlocated on the lenses of the lens. This can be dust, scatter from the cleaning fluid, scratches, air bubbles in the optical glass, peeling off enlightenment, anything. Dirt can be not only on the front or rear lens, a similar effect is obtained from dirt on the inner lenses of the lens.
- The dirt that is visible on the circles of blur is not displayed on objects in the field of sharpness. Similarly, the diaphragm blades, their appearance and shape, not displayed on objects in the field of sharpness during everyday shooting.
- The dirt on the lenses works like aperture device, and just like the diaphragm blades are displayed on circles of blur, this dirt is also displayed on them.
Questions for which I do not have an exact answer:
- Do special elements (aspherics, low dispersion and other types of glasses) affect bokeh artifacts?
- Concentric circles on circles of blur come from poorly polished lenses? If not, then why? Example of such circles.
- Can a service center be required to have lens prophylaxis if severe 'bokeh contamination' is detected?
Leave your answers in the comments.
↓↓↓ Like it :) ↓↓↓ Thank you for your attention. Arkady Shapoval.
Porridge and hair are not enough on the lens.
and cat hair)))
and fungus ..
and semen rhino
Flame ban_set
XD
Concentric circles resemble interference ...
smc-da pentax 18-55 al shot right out of the box with some kind of dirty bokeh, sort of. Damage to the anti-reflective coating is also reflected on the side. Therefore, if the lenses are clean on the outside, and there are scratches in the side, it is likely that the lens was not very carefully opened.
Interesting ... It turns out to be a very good way to check the lens for all sorts of sores such as dust / fungus / scratches and other nasty things that are not very noticeable to the eye.
I read a lot of controversy and arguments in favor of the fact that a certain amount of dust and dirt almost does not affect the quality of the pictures. Even the lenses were specially scratched. He himself sacredly believed in this because he did not bother, especially with filters. Maybe it doesn’t influence much if the object is in the field of sharpness, but on the bokeh and the objects are out of focus it looks like any speck of dust is affected. Microbubbles in lenses can probably also influence, and all that refracts / delays / reflects light.
PS Wasn't it scary to screw it into the carcass with salt? Abrasive after all ... Maybe by the way after that the lens never returned to its original form.
The lens returned to normal :)
"It may not be much of an effect if the object is in sharpness, but bokeh and objects out of focus seem to be affected by any speck of dust."
No, dust particles do not affect, even iron chips will not give a visible result. More affected by MS defects and stains. For clarity, I will say that the bokeh circle is a small display of your lens and one speck of dust cannot give such an effect: https://radojuva.com.ua/wp-content/uploads/2015/01/boken-dust-test-1.jpg on a lens with a large aperture. This cherished speck of dust can be displayed on lenses with a small diameter rear lens and low aperture. But only on such lenses bokeh is not in the first place. And in the photo, most likely divorces
I can assume that the cocentric circles in the bokeh may be misaligned / misaligned (violation of the optical axis, due to impact / repair / time due to micro-movement of the lenses) of the lens. May also affect the sharpness of the entire lens. Your version also has 100% "right to life".)))
About concentric circles. Today I was lying on the balcony, it is southern, the sun was shining bright, there were no clouds in the sky, the windows were wide. I was lying on the couch in the sun, but so as not to be blind, I put my hand over my eyes. The hand is hairy. And now I see on the ends of my hair - such very bright circles. I looked closely for a long time, but then I looked a little further behind the hair at the landscape and immediately turned the focus to the circles - they became large, concentric circles are visible in them, I counted 8 (eight) but they are endless, very small towards the center. and if you look at them for a long time without changing either the position of the eyes, let alone the head, you can see how the circle pulsates due to the change in the focus of the eyes. I will try to describe the circle precisely. Edge edges are like fractals edges. The whole is very bright and the edges are even brighter, the color is golden, the circles inside are very clear with thin borders. I was especially impressed by the edges of the circles - like millions of small stars stuck to the edges, and the inner circles that go inward endlessly.
After NG still not let go? ;)
It was really very beautiful, like in computer games. I do not use drugs, I do not smoke, I drink on holidays.
Although your revelations are alarming)), but I envy your worldview. And lately I've seen everything in gloomy tones. And the farther the worse.
Why are you alarmed here? Next time I’ll take a picture, I’ll specially fix my hair by 5 cm, the sun’s rays will reproduce everything, then these bokeh-fractals-concentric circles-stars on the edges will impress many.
Don’t worry, I'm joking, my mood is good. :)
The fractal that you observe is diffraction. There is such a school experiment: "observing the diffraction of waves at the tip of the needle located between the eye and the candle."
The thought was - that would take a picture, mdf needs about 5 cm.And about fractals too - how to take a picture of them and where
To fill up the lens with salt is of course bold. Salt dust after cleaning will remain, attract water ... ..He will not live for a long time. Salt + humidity + metal will do their dirty work. "2. Dirt visible in the circles of confusion does not show up on objects in the field of focus" is a bold statement. Sharpness and contrast in the field of focus in your examples will suffer for sure. This is not a scratch or a couple of dust particles.)
This is not about such dirt as shown in the examples, but about ordinary fine dust particles, which in real conditions do not affect the photo in the sharpness zone. As for the stained Hindu, believe me, he will still survive both me and you.
It remains only to pray for him.)
ogospade - salt is not an acid, it will rinse with distilled water and that's it, the salt will go away. like catch less salt by the sea. what the ***
Your cars rot in the winter because the roads are watered with sulfuric acid.
Some lenses (I looked at the tests), give "onion bokeh", I doubt that this is a bad grinding of the rear lens.
No, their lens is not round, but a lemon.
Doesn't the spherical aberration called “coma” affect?
No, what are you! This is all because the lenses are not round!
On the first question. I'm sure that specific elements - low-dispersion glasses, aspherical elements - do not greatly affect the nature of the blur. The only thing is that the aspheric removes the SfA, so the circles become even monotonous (for example, Zenitar-M, it is quite good in terms of the SfA) and WITHOUT a lighter edging, like in the Tessars (this is especially evident in the I-29, which suffers greatly from SfA). And low-dispersion glasses, they are also ED (Extra low Dispersion), are components of a- and apochromatic glues - doublets and triplets, respectively. Those. the presence of these elements (yes, in fact, it's just a kind of glass, such as a phosphate crown) implies a decent CA correction. How is she in bokeh - I did not notice. It doesn't seem to affect the circles of confusion.
And I took off the bokeh on my smartphone, in macro mode, damn it, no lemons, everything is perfectly round, and some of them even have multiple beams ... A thought flashed - what the fuck is my DSLR.
It seems that there are lens attachments for smartphones to make bokeh without self-torture or all the same, the size of the matrix solves everything. Tell me, if in the know.
Nozzles - yes, bokeh won't work (or not quite right, but you can); the size of the matrix decides when it is important.
By the way, here's what you can shoot on a smartphone.https://hi-tech.mail.ru/news/22-best-iphone-pics.html.... Personally, I have a double feeling from viewing these photos.
Concentric circles - et xs. M. b. blooper on the protective filter or front lens.
Bokeh circles are not Newton's Rings? Very similar, as in some lens designs certain lens groups can have a similar effect.
https://ru.wikipedia.org/wiki/%CA%EE%EB%FC%F6%E0_%CD%FC%FE%F2%EE%ED%E0
like this? here one wise guy said that this is diffraction from school experience with a candle and a needle in the eye
What you observed at the tip of the hair from your ... hand is the diffraction of light with its subsequent interference. Light waves go around the hair, the boundaries of the hair become secondary sources of waves, behind the hair, light waves from several sources are superimposed on each other, a pattern of alternating bright and dark circles occurs (the waves either reinforce each other or extinguish each other).
“Newton's rings” is an interference pattern from the re-reflection of light waves between two surfaces of different degrees of curvature. Two waves with different phases arise from one wave, and depending on the distance from the center of the lens, the pattern of alternating bright and dark circles occurs in the same way.
Now why am I guessing that the circles on the bokeh are not diffraction but possibly “Newton's rings”. Diffraction in the camera also takes place, as a result of the light bending around the obstacle-diaphragm, but the effect of diffraction has already been completely studied and understood, in the picture it is visually expressed only in the loss of sharpness. The diameter of the diffraction spot is expressed in several pixels. But the interference of light from a poorly matched radius of curvature of the lenses in a group can have an effect over the entire diameter of the lens, and theoretically can lead to such bokeh rings, as Arkady led.
Will there be more sarcasm? Or was it such a joke too? Could you suggest your versions with hair and bokeh other than “divine intervention”?
Do you understand what you wrote yourself? : The diameter of the diffraction spot is expressed in several pixels :. Let it be known to you that if the DDP is> = “area of several pixels”. then the photo will be soapy, like soapy water. And why are you signing this with Arkady? He created a blog. I don't know exactly what it is. Maybe this is both, or maybe just this or only that. But how do you explain fractals along the outer radius? And there really are fractals and not some Newtons with needles. Maybe divine intervention, or rather just his work. But while there is no photo there is nothing to discuss. Now, if someone brought a corresponding photo. And then the sun has gone somewhere and clouds with clouds in the sky.
It’s somehow not interesting to argue with you at all, you have only your own subjective denial for any arguments.
About DDP you can read the link. The smaller the aperture, the larger the diffraction spot. At the end of the page, you can see firsthand the f / 22 diffraction spot with a diameter of almost 5 pixels. The image is blurred in practice from diffraction, more or less, although the sharpness of the image is affected by a lot of things even without diffraction.
http://vladimirmedvedev.com/grip.html
PS Where am I signing up with Arkady? The fact that I referred to the rings in the bokeh in the photo of Arkady and on his own question # 2 - did I “subscribe” to them? IMHO you are a golimy troll who argues just for the sake of argument, without giving weighty counterarguments and without introducing a single share of constructiveness on his part. Hair fractals are of course interesting, but they do not answer any question asked by Arkady at the end of the article, and does not even bring the answer closer.
Outside the window is Christmas, and on Radozhiva bas_set.
Do not forget about the construction of the eye, as I understand it, that the fractal was seen by a person with the eye and not in the photo. The pupil we have is comparable to the diaphragm, so look at your pupils (even edges or flaws).
The end of the lens, and if salt gets into the camera ...
read the basics of general chemistry. A huge amount of sodium chloride is dissolved in seawater. The world's oceans contain 4 × 1015 tons of NaCl, that is, from every thousand tons of seawater, an average of 1,3 tons of sodium chloride can be obtained. Traces of NaCl are constantly present in the atmosphere as a result of the evaporation of spray from seawater. In clouds at an altitude of one and a half kilometers, 30% of droplets larger than 10 microns in size contain NaCl. It is also found in snow crystals. And what? No one at sea takes a camera, does not shoot snow in winter? the end of the lens can be if this lens is your eye and pour salt into it
I do not have such knowledge in chemistry, but salt causes corrosion of metal parts, I know that.
Pour salt into your eyes.
How is it no knowledge. Do you have an eye, i.e. a metal lens? Then you are the Lumberjack
why repeat this bad mantra?
Oh, Anonymous, what about all such alarmists, this is the Soviet lens, it can only go bad in the mouth of Orodruin, just like my d80 :).
Yeah. I saw how the Nikon lenses were hammered into the nails and nothing ... not even cracked. And the Soviet is a quality that will survive many. Then they knew what standards and GOSTs were ...
Well, at least they knew how to cook steel in the USSR ...
They knew that, but they did not observe it. Five of my Nikon lenses fit into the bayonet like a glove, even two sets of Chinese macro rings, and these are six pieces, and each individually fits perfectly and is removed (specially tested), and only one heroic HELIOS-81n, like Zhiharka from a fairy tale, his arms spread out his legs , so as not to get into the stove, and he always strives first not to get in, and then not to get out.
And there is a hole in the old woman.))) Anything can happen ...
My HELIOS-81n behaves similarly :)
With drops of water, it turned out interestingly. :)
About a year ago, looking at similar pictures, I noticed the silhouette of a small insect on the circles, it was a surprise, and even later we saw each other again in the viewfinder. More our paths did not intersect))
Arkady, what about the dust inside the lens? On my Nikkor 1.8 / 50 AF I "licked" both the rear lens and the front one, but all the same, in the circles of confusion, a couple of small dots are noticeable, and barely noticeable round specks, transparent.
The article also states:
"A similar effect is obtained from dirt on the inner lens elements."
sure missed
Do you print photo books yourself or give them to print to other people?
I heard that it is possible to illuminate with a flashlight through the lens with an open aperture, then it will show its purity ...
when we turned off the lights, I did so, checked, the fungus and dirt are fine
All with Christmas, yesterday I photographed a glass of champagne against the background of a Christmas tree and on the tree a garland with multi-colored lights and I got dirty bokeh but not on all the circles the same where more and where less and I got scared they say a dirty lens and picked up another lens and made the same the photo and dirt on the bokeh remained in the same places, I made the following conclusion that since the garland on the tree and on the tree, the needles obscure some of the light, these same needles and give the dirt on the side, the dirt on the side is not only objects (garbage) on glass obye tive and objects from the camera and lights up themselves
Can the garland be dirty?
Arkady, I noticed that people are looking for active, that is, new topics, and put in their questions that may not be on the topic but they really concern them, and because new topics are actually discussed, they write there, and sometimes to the old ones topics, you can see them there, like trash. There is 1 question and 1 sentence:
The question is - is there a cleaning of the comments?
Suggestion - to create a topic / thread / article - like "flood / offtopic / quick question for the photographer", where you could get quick answers, and where you could ask such questions like:
"I'm a g * fotographer, how can I become a professional?"
"What and where do you print?"
"Buy better D810"
and so on.
For the most curious https://radojuva.com.ua/2013/04/faq/ 60% of comments make me nauseous. No flame, flood and offtopic! And so the whole Internet is filthy. First of all, those who concern politics on the pages of Radozhiva are ruthlessly banned.
Vasily show you a photo or send a garland for study
You can at least have a photo.
Mine here:
This is Nikon 1 J1 + MC Triplet T-3 2,8 / 80 Etude-2c Diaproektor Export
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1. http://src24.ru/ev
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2. http://src24.ru/e6
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3. http://src24.ru/eH
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4. http://src24.ru/eS
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5. http://src24.ru/eE
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6. http://src24.ru/eR
Browsed the Internet in search of those same concentric rings in bokeh, for example, the M.ZUIKO Digital ED 14-42mm f3.5-5.6 EZ lens. And in one of the reviews I saw them, at the end of the page on the second link - the top right picture. Despite the poor picture quality, we can say with 99% certainty about the interference nature of the rings (enlarge the picture).
http://img.photographyblog.com/reviews/olympus_m_zuiko_digital_ed_14_42mm_f_35_56_ez/bokeh2.jpg
http://www.photographyblog.com/reviews/olympus_m_zuiko_digital_ed_14_42mm_f_35_56_ez_review/
https://vk.com/album114445294_177637208
this is a link to my photos in contacts, how to put a specific photo, I didn’t think much here,
but even by clicking on the link at the end you can see a photo on the New Year theme with that blurry_ dirty bokeh, so this tree will be always glad to see the whole vein
And what to think about, I always have hosting in my bookmarks, it’s very convenient. Really some kind of dirt on the lenses
the lenses are clean this tree because when the dirt is all circles with garbage and here only a few
And for me - if you raise ISO to 800, then the noise reduction eats everything, and the fungus with mold, and the dirt eats. But on the 3rd, 4th and 100th photo Iso XNUMX and the balls are clean, xs
Concentric circles are likely to be traces of not completely removed contamination, i.e. Simply put, not completely wiped off.
It is not difficult to check - breathing and stains, as a rule, become visible.
And I have Helios-81N, it still works like a Kalashnikov assault rifle. And I got another one, just released later, so the diaphragm does not close well on it, it seems that there is a lot of lubrication and it has frozen. And my dear, I have already worked since 1987 without failures. And now I use it on Nikon. And it gets on the camera and is shot like clockwork! This is me to the fact that Helios-81N was mentioned here.