Out of focus light circles of Nikon AF-S 50mm/1.8 show 2 dark stripes

Goreb · Jan 5, 2017

Hi there,

recently I was doing some photos from our Christmas tree and was using my favourite Nikon AF-S 50mm 1.8. I like this lens very much as all the Bokeh is perfectly fine. However when I was using it wide open I got some strange out of focus behaviour, which I could not observe with any of my other Nikon/Sigma lenses.

The attached photos should illustrate my questions: In each of the out of focus circles I see 2 darker stripes. The aperture was around 1.8 to 2.2. The more I step down the more it disappears. However the plan was to take pictures with a completely wide open aperture and the results look really weird.

Example for the 2 darker stripes on the out of focus circles

Another example for the 2 darker stripes on the out of focus circles

After observing this I was not sure is it the camera or is it the lens. So I attached the AF-S 50mm/1.8 to both of my cameras the D500 and the D90. Both show the same results. Additionally I checked all my Nikons and Sigmas and none does have the same behaviour with the 2 stripes. Among them is also the Nikon AF-S 35mm/1.8 and the Nikon AF-S 85mm/1.8. Both lenses show awesome results here. Also the Nikon 16-80mm/2.8-4.0 is perfect under the same conditions as well as the Sigma 17-50mm/2.8 and many others.

Does anyone have a suggestion what the reason could be ? The result looks a bit irritating to me. To use these pictures for anything I would need to do a lot of post work which is tedious or even impossible...

Thanks for any suggestions, Heiko

Barlowephoto · Jan 6, 2017

Hi Goreb. Reading your description, it certainly seems your Nikkor 50mm/1.8 lens is suspect. Are you using a filter on the lens? I would remove the filter.

Additionally, I would check the lens for those two stripes, by removing the lens from the camera, holding the aperture wide open ( holding the pin on the back of the lens ) and shining a small flashlight through the lens while observing the inside glass elements within the lens. It would seem that you may have 2 very deep scratches somewhere on a glass surface. Bokeh irregularities can usually be traced to lens glass surface dirt or damage ( or filter irregularities ). Hope this might help....................Jeff Barlowe

Marianne Oelund · Jan 6, 2017

Barlowephoto said:
Hi Goreb. Reading your description, it certainly seems your Nikkor 50mm/1.8 lens is suspect. Are you using a filter on the lens? I would remove the filter.

Additionally, I would check the lens for those two stripes, by removing the lens from the camera, holding the aperture wide open ( holding the pin on the back of the lens ) and shining a small flashlight through the lens while observing the inside glass elements within the lens. It would seem that you may have 2 very deep scratches somewhere on a glass surface. Bokeh irregularities can usually be traced to lens glass surface dirt or damage ( or filter irregularities ).

All sound advice.

To the OP:

Bokeh circles from point light sources will reveal many details about the condition and quality of your lens. It is even possible that you are seeing the result of a manufacturing flaw on one of the lens surfaces - but let's hope that's not the case, and it is just some foreign material that can be removed by cleaning.

Let us know if you are able to identify the cause.

--
Source credit: Prov 2:6
- Marianne

Leonard Shepherd · Jan 6, 2017

Goreb said:
However when I was using it wide open I got some strange out of focus behaviour, which I could not observe with any of my other Nikon/Sigma lenses.

The attached photos should illustrate my questions: In each of the out of focus circles I see 2 darker stripes. The aperture was around 1.8 to 2.2. The more I step down the more it disappears.

Example for the 2 darker stripes on the out of focus circles

Another example for the 2 darker stripes on the out of focus circles

After observing this I was not sure is it the camera or is it the lens. So I attached the AF-S 50mm/1.8 to both of my cameras the D500 and the D90. Both show the same results. Additionally I checked all my Nikons and Sigmas and none does have the same behaviour with the 2 stripes. Among them is also the Nikon AF-S 35mm/1.8 and the Nikon AF-S 85mm/1.8. Both lenses show awesome results here. Also the Nikon 16-80mm/2.8-4.0 is perfect under the same conditions as well as the Sigma 17-50mm/2.8 and many others.

Does anyone have a suggestion what the reason could be ?

If you mean the horizontal dark area in the light source bottom left in the first picture and centre in the second picture they may be out of focus light bulbs which are not fully illuminated top to bottom. If this is right the effect would reduce on stopping down, which you say is what happened.

The effect might not show with different focal length lenses as the depth of field and angle of view are different.

--
Leonard Shepherd
Good photography is usually more about what you do with the equipment you own rather than what equipment you own.

Marianne Oelund · Jan 6, 2017

Leonard Shepherd said:
Goreb said:

However when I was using it wide open I got some strange out of focus behaviour, which I could not observe with any of my other Nikon/Sigma lenses.

The attached photos should illustrate my questions: In each of the out of focus circles I see 2 darker stripes. The aperture was around 1.8 to 2.2. The more I step down the more it disappears.

Example for the 2 darker stripes on the out of focus circles

Another example for the 2 darker stripes on the out of focus circles

After observing this I was not sure is it the camera or is it the lens. So I attached the AF-S 50mm/1.8 to both of my cameras the D500 and the D90. Both show the same results. Additionally I checked all my Nikons and Sigmas and none does have the same behaviour with the 2 stripes. Among them is also the Nikon AF-S 35mm/1.8 and the Nikon AF-S 85mm/1.8. Both lenses show awesome results here. Also the Nikon 16-80mm/2.8-4.0 is perfect under the same conditions as well as the Sigma 17-50mm/2.8 and many others.

Does anyone have a suggestion what the reason could be ?

Click to expand...

If you mean the horizontal dark area in the light source bottom left in the first picture and centre in the second picture they may be out of focus light bulbs which are not fully illuminated top to bottom.

No, the OP is referring to the two near-horizontal and parallel fine dark lines which are visible in all of the blur circles from background lights (not the foreground lights). Scan through his samples at 100% view and you will see them clearly.

--
Source credit: Prov 2:6
- Marianne

PatMann · Jan 6, 2017

Those lights are clearly alien robot spies. I would get them out of there right away.

PatMann · Jan 6, 2017

But seriously, this is a very strange effect. Has to be some opaque stripe in or on the lens or filter.

MrScrooge · Jan 6, 2017

PatMann said:
Those lights are clearly alien robot spies. I would get them out of there right away.

Leonard Shepherd · Jan 7, 2017

Marianne Oelund said:
No, the OP is referring to the two near-horizontal and parallel fine dark lines which are visible in all of the blur circles from background lights (not the foreground lights). Scan through his samples at 100% view and you will see them clearly.

Thanks for helping clarify

As the lines are at an angle they might be scratches on a filter (if used), the lens or maybe even the sensor.

These 2 black lines at an angle with equal spacing are most likely some sort of scratches somewhere in the system.

steras · Jan 7, 2017

The two lines shift position withing the blur circles as one moves from left/right and top/bottom.

embie · Jan 7, 2017

IMO it's a effect due to the manufacturing of the lightball materials.

How can "a" scratch on a lens or filter make these lines ONLY in the lightball circles, scratches don't choose their subjects.

briantilley · Jan 7, 2017

embie said:
IMO it's a effect due to the manufacturing of the lightball materials.

I don't think so - but it would be easy to check. Just take the same shot again but with the camera rotated 90 degrees. If the marks stay at the same angle in the photo then you're correct, but if (as I expect) they are also rotated by 90 degrees, it's something in the camera, the lens or a filter.

Leonard Shepherd · Jan 7, 2017

briantilley said:
Just take the same shot again but with the camera rotated 90 degrees. If the marks stay at the same angle in the photo then you're correct, but if (as I expect) they are also rotated by 90 degrees, it's something in the camera, the lens or a filter.

This would narrow down the options.

Marks on a surface within a lens system are not in the same plane as the image on the sensor, and could appear or disappear (as the OP reports) with different amounts of out of focus diffusion at different apertures.

Another option is to examine the lens front and rear and maybe even the sensor using a magnifier to look for any marks or scratches.

Hanno van Tartu · Jan 7, 2017

Marianne Oelund said:
Barlowephoto said:

Hi Goreb. Reading your description, it certainly seems your Nikkor 50mm/1.8 lens is suspect. Are you using a filter on the lens? I would remove the filter.

Additionally, I would check the lens for those two stripes, by removing the lens from the camera, holding the aperture wide open ( holding the pin on the back of the lens ) and shining a small flashlight through the lens while observing the inside glass elements within the lens. It would seem that you may have 2 very deep scratches somewhere on a glass surface. Bokeh irregularities can usually be traced to lens glass surface dirt or damage ( or filter irregularities ).

Click to expand...

All sound advice.

To the OP:

Bokeh circles from point light sources will reveal many details about the condition and quality of your lens. It is even possible that you are seeing the result of a manufacturing flaw on one of the lens surfaces - but let's hope that's not the case, and it is just some foreign material that can be removed by cleaning.

Let us know if you are able to identify the cause.

embie · Jan 7, 2017

Hanno van Tartu said:
Marianne Oelund said:

Barlowephoto said:

Hi Goreb. Reading your description, it certainly seems your Nikkor 50mm/1.8 lens is suspect. Are you using a filter on the lens? I would remove the filter.

Additionally, I would check the lens for those two stripes, by removing the lens from the camera, holding the aperture wide open ( holding the pin on the back of the lens ) and shining a small flashlight through the lens while observing the inside glass elements within the lens. It would seem that you may have 2 very deep scratches somewhere on a glass surface. Bokeh irregularities can usually be traced to lens glass surface dirt or damage ( or filter irregularities ).

Click to expand...

All sound advice.

To the OP:

Bokeh circles from point light sources will reveal many details about the condition and quality of your lens. It is even possible that you are seeing the result of a manufacturing flaw on one of the lens surfaces - but let's hope that's not the case, and it is just some foreign material that can be removed by cleaning.

Let us know if you are able to identify the cause.

Click to expand...

Leonard Shepherd · Jan 7, 2017

Hanno van Tartu said:
Richard Haw has written an article that includes a section on what one may learn about a lens from bokeh circles: https://richardhaw.com/2016/12/24/study-damaged-lens-artifacts/

Interestingly this link starts with a similar single line to the OP's two lines and concludes

"Dirt 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"

Edit - posted just 1 minute after the previous post - we agree the richardhaw conclusion is the most likely cause.

--
Leonard Shepherd
Good photography is usually more about what you do with the equipment you own rather than what equipment you own.

embie · Jan 7, 2017

Leonard Shepherd said:
Hanno van Tartu said:

Richard Haw has written an article that includes a section on what one may learn about a lens from bokeh circles: https://richardhaw.com/2016/12/24/study-damaged-lens-artifacts/

Click to expand...

Interestingly this link starts with a similar single line to the OP's two lines and concludes

"Dirt 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"

Edit - posted just 1 minute after the previous post - we agree the richardhaw conclusion is the most likely cause.

Marianne Oelund · Jan 7, 2017

embie said:
This type of scene build-up should be a "test setup" before buying second hand lenses ;-)

The problem is that the test is so sensitive that it reveals qualities of the lens which have no impact on photography. If used by people who do not understand optics very well, they risk rejecting perfectly good lenses.

This kind of thing could raise "scandals" that would make the long history of AF fine-tuning woes look like a minor annoyance.

BasilG · Jan 7, 2017

Leonard Shepherd said:
Marianne Oelund said:

No, the OP is referring to the two near-horizontal and parallel fine dark lines which are visible in all of the blur circles from background lights (not the foreground lights). Scan through his samples at 100% view and you will see them clearly.

Click to expand...

Thanks for helping clarify

As the lines are at an angle they might be scratches on a filter (if used), the lens or maybe even the sensor.

These 2 black lines at an angle with equal spacing are most likely some sort of scratches somewhere in the system.

Probably not the sensor given that a) they disappear when using other lenses and b) appear on two cameras when that lens is used on them...

Marianne Oelund · Jan 7, 2017

embie said:
IMO it's a effect due to the manufacturing of the lightball materials.

There are no lightballs. There are pinpoint sources of light, which appear as "balls" since they are far out of focus.

Member said:
How can "a" scratch on a lens or filter make these lines ONLY in the lightball circles, scratches don't choose their subjects.

The bokeh circles ("lightballs") are images of the lens exit pupil. Anything in the lens, at or near the aperture diaphragm, casts its shadow into the bokeh circle.

Out of focus light circles of Nikon AF-S 50mm/1.8 show 2 dark stripes

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