Study: Damaged Lens Artifacts

Happy holidays, everybody! I wasn’t able to update the blog last weekend since I was busy and I had to work last Saturday. This coming Christmas is no different for me because I am going to have to work as well. This is Japan and Christmas is nothing more than a Western idea celebrating capitalist ideals. Speaking about Christmas, I have an assignment for you guys this season if you have ever bought an old lens or have inherited one. Read along!

Damaged Lens Artifacts:

Today, I will show you how to check wether a damaged lens element will affect an image or not by using light sources like Christmas lights! Some people claim that damage on a lens’ optic will not show up in the final image, while it is true for minor problems like a patch of fungus it is not true for something more serious like a scratch or chip. Sellers and people on the internet make this claim and I will show you how to test their statement by doing these simple tests.

Dirty Bokeh:

Some damages that are too feint to see with the naked eye without using the help of a light source such as a torch can fool you into thinking that nothing is wrong with a lens but this simple bokeh test can help you determine wether the lens is still OK or not. This test only works in darkness so I do this at night or inside a dark room.

First, focus your lens to it’s minimum focusing distance and stand 1.5-2m away from some Christmas lights or any bright sources of light. This also works on light sources that are far away like some street lamps 60m meters away from you. So long as you can produce clean and clear bokeh balls you are on the right track.

Second, set your lens to it’s maximum aperture and set your exposure settings so that you will get a nice picture with bokeh balls, ISO400 at 1/250s usually works for me. The key to this is to underexpose the bokeh balls a bit so that things will show up.

Examine your picture and zoom into your bokeh balls and look for artifacts. The following images show a few examples of bad bokeh from some of the lenses that I encountered.

HAW_5000.jpgDirt or a bad scratch can cause this artifact to appear. Depending on the cause, it can easily be fixed by cleaning the lens elements in case of dirt or having a professional re-polish the problem element for you and re-coat it after. This particular lens looks immaculately clean but as you can see from the picture above, the lens produces bad bokeh. I am yet to open it again to find the cause but I suspect that a minor scratch in the coating is the cause.

Some people are saying that damage on the front element is not going to affect the image much even if you removed a chunk of glass from it. Don’t believe it. Even a smaller crack is able to cause some sort of artifact in your bokeh balls. While it is true that it might not affect some lens designs much but with the right conditions you can make it appear on the images produced by the lens.

Cleaning marks that look like swirl marks will not affect the image much if they are not deep enough so do not worry too much about these. If the said swirl marks can be felt by running your nails on the surface of the lens, skip it or ask for refund. Those may show up!

haw_1577The irregular line on the edge of the bokeh is caused by lens separation while the feint dots that you see in each bokeh ball is caused by dirt or bubbles in the lens cement. The dirt is in another element so it’s not as well-defined as that irregular line. Fungus can also cause similar dots to appear in your bokeh balls because they block light or they ate the coating away, leaving a bald spot on the coating.

haw_4119Some more examples of dirty bokeh. I have serviced a lens some time ago and it has some bad irregular-looking marks in the front element that is deep enough to be felt by my nails when I ran it on it’s surface. The mark is replicated in each bokeh ball. If the said irregular marks resemble the face of Jesus as portrayed in the paintings then the Vatican would’ve called my lens miraculous and I can earn money by charging devotees to buy prints of my bokeh balls. This is all made in jest but you get the idea.

Irregular blobs:

Irregular blobs or ghosts are formed when one of the lens elements has a chip on the edges or the surface. These blobs usually look like spheres or a sharp but even teardrop but a lens with a chipped element will show something different.

HAW_0332.jpgA chip in any of the lens elements will produce an irregular-shaped blobby artifact when it is shot against a bright light source and it will coincide with where the chip is located. The distribution of light is not even due to the chip and that causes these things to appear.

Chips can be hard to discover when it is situated around the edge of the lens element since it is covered by it’s retention ring or whatever is used to secure it. Shining a small torch’ll show these while you peek at the lens at an angle. Even with this technique, a small chip will not show up easily and you may misdiagnose it as oil or cement separation.

Hazy images:

A lens with haze caused by crazing of the element’s surface due to chemical or mechanical means will affect the resulting image made from that lens. Haze from condensation or oil will also affect the lens similarly. Haze is easy enough to detect so I will not explain how to do it. This is easy to fix if it’s just condensation or dirt.

haw_4132The image looks fine here but is hazy overall, making the contrast low and the image a bit washed-off. Some people actually like this and they buy “soft focus” filters just to get this effect to make their images look dreamy.

haw_4135Shooting away from the sun might be fine but check out that bright reflection found in the upper-left hand corner of the image. The reflection looks like a dull hazy bloom instead of a nice sunstar. The lens is stopped-down to about f/5.6 in this image so I expected a pretty sunstar to appear but instead I got this ugly grey blob.

haw_4137Here is another example of the milky haze that forms in bright highlights or reflection. It is very unnatural because the highlight is diffused.

haw_4141Over-exposing the shot might give you a nice hazy veil over your image, resulting in a very dreamy image. Directors of photography would use a filter smudged with petroleum jelly to achieve this same effect. I would certainly use this technique for a bride in her wedding dress (if it’s white). This is certainly an unwanted effect but you can certainly use this for your creative needs.

haw_4148Here is another example of the flaw used to it’s advantage, just imagine if the street’s wet!

Psychedelic Images:

This is probably the easiest to fix since nothing is damaged when you find that your lens is producing images like it was made with a Petzval lens. This is just some repair guy putting the lens back incorrectly and if you know the sequence of the lens elements than you can fix this yourself if you have the experience and tools.

The image below is the result of me putting back a lens element facing the wrong direction and I ended up with a uniquely weird lens.

haw_0502Now I got myself an “ART” lens. People pay a lot of money to buy that Petzval lens but now you can modify your own lens to achieve something similar for free! It is very trippy but this is not how this lens is supposed to perform so I had to fix it.

Lenses with an element facing the wrong direction would have the center usually in focus but the rest of the image is blurred in a funky way. You can position the lens a few inches above a piece of white paper under a light source and if you see uneven refraction on the paper, then that is one sure indication that one of the lens elements is not facing the right direction. Uneven refraction will show as a bright/dull spot in the middle of the resulting bright area on the piece of paper. A normal lens should give you even illumination.

I once reversed one of the lens elements on one of my primes on purpose to reproduce this effect and I ended up with a lens that is VERY sharp even wide-open but the focusing is off as it will not focus past 10m or so.


This post is not enough to cover a topic this broad but I tried to put the most common ones here and how to make them appear. While the dirty bokeh balls won’t be visible in normal daylight shooting conditions, it will certainly appear in dark conditions where the bokeh balls is most obvious. If your lens has this dirty bokeh problem and you need to show some bokeh in your pictures, be sure to overexpose the scene a bit so that the bokeh balls will be bright enough to hide whatever flaws that can appear within each of them.

The hazy look can be avoided by not shooting against the sun or not having any reflections of bright things or bright any lights in the scene and just like my samples above, you can even exploit this flaw to produce unique looking pictures.

The last problem is possibly the hardest one to avoid because the optical formula is wrong to begin with and it will show in all lighting conditions.

I hope that you enjoyed this short article. I will continue next with an important telephoto lens for Nikon and I need time to prepare for that so I will not be publishing anything next week but I may find some time to publish it in the coming new year’s vacation so check my  blog and see if something is published or not. Alternatively, you can “like” the companion facebook page of this blog and get updates on what is published or interact with other guys who are also into the same thing.

That’s it for this week! Now it’s time for me to get a power nap! Love, Ric.

Help Support this Blog:

Maintaining this blog requires money to operate. If you think that this site has helped you or you want to show your support by helping with the upkeep of this site, you can simple make a small donation to my account ( Money is not my prime motivation for this blog and I believe that I have enough to run this but you can help me make this site (and the companion facebook page) grow.

Helping support this site will ensure that this will be kept going as long as I have the time and energy for this. I would appreciate it if you just leave out your name or details like your country and other information so that the donations will totally be anonymous it is at all possible. This is a labor of love and I intend to keep it that way for as long as I can. Ric.


5 Comments (+add yours?)

  1. Peter Ng
    Feb 02, 2017 @ 09:13:00

    Really interesting as I start collecting non AI lenses and wondering how to store and upkeep them, Richard. Thank you for documenting and sharing.


    • richardhaw
      Feb 02, 2017 @ 09:17:01

      Hello, Peter.

      Just make sure that you keep them in the drybox and see to it that the moisture level is not high. This is not a sure way to prevent fungus because it can sometimes form even when kept in a dry place. For better measure, I add the chemical that I mentioned in my post as a fungal retardant. They are cheap and you can buy them from the camera shops. Still, the best way is to use your gear from time-to-time and let sunlight do it’s job and keep away the stale air. Ric.


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