What are causing these artifacts that become prominent in lens flares?

[Mike Mali]

Hi,

I took some photos with lens flares to see how the coatings perform on this lens I purchased. I really love the colors but I'm noticing some artifacts when the lens flares. I'm thinking the very prominent ones that are squigly look like dust. The ones that are dots also seem like small speckles of dust. Also there is a small amount of haze near the rear element. Would that contribute to these artifacts?

Camera: Fuji XT2

Lens: Olympus OM Zuiko 40mm F2

Aperture: F2

Shutter speed and ISO are in the metadata on the photo

Thanks,

Mike



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Picture 2 (with artifacts not pointed out with red arrows)

 

[Holger Bargen]

Hi,

I took some photos with lens flares to see how the coatings perform on this lens I purchased. I really love the colors but I'm noticing some artifacts when the lens flares. I'm thinking the very prominent ones that are squigly look like dust. The ones that are dots also seem like small speckles of dust. Also there is a small amount of haze near the rear element. Would that contribute to these artifacts?

Camera: Fuji XT2

Lens: Olympus OM Zuiko 40mm F2

Aperture: F2

Shutter speed and ISO are in the metadata on the photo

Thanks,

Mike



Picture 1 (artifacts not pointed out)



Picture 1 (with artifacts not pointed out with red arrows)



Picture 2 (artifacts not pointed out)



Picture 2 (with artifacts not pointed out with red arrows)

Looks like dust on the sensor.

 

[alcelc]

[No message]

 

[kenw]

Huh, as you and others point out that sure looks like sensor dust. But you say you shot at F/2.0? Would usually not expect to see dust at that aperture.

Are you certain the lens was set to F/2 for these shots? The exposure seems to imply something more like F/8 (you have 1/3200 shutter speed at ISO 400 in daylight) but that's a coarse estimate. And doesn't seem like enough out of focus blur for F/2 on an APS-C, but again easy to get fooled here.

I presume you've tested with a different lens stopped down to F/16 or so to check that there isn't any sensor dust?

As to the flare that is indeed pretty bad but if their is a hazy lens element that could be expected.

--
Ken W
See profile for equipment list

 

[hotdog321]

You have a dust speck on the sensor. First try using a rocket blower and the camera's self-cleaning mechanism (if it has one). This normally does the trick, but if it is still stuck, you'll have to do a wet clean.

 

[Mike Mali]

Thanks for the reply! I appreciate it!

 

[Mike Mali]

Huh, as you and others point out that sure looks like sensor dust. But you say you shot at F/2.0? Would usually not expect to see dust at that aperture.

Are you certain the lens was set to F/2 for these shots? The exposure seems to imply something more like F/8 (you have 1/3200 shutter speed at ISO 400 in daylight) but that's a coarse estimate. And doesn't seem like enough out of focus blur for F/2 on an APS-C, but again easy to get fooled here.

I presume you've tested with a different lens stopped down to F/16 or so to check that there isn't any sensor dust?

As to the flare that is indeed pretty bad but if their is a hazy lens element that could be expected.

Hey Ken,

I shot wide open and tried to shoot near close focus. I noticed on a few other photos that the dust particles only show up when the lens flares heavily and would disappear when there would be no flares.

Thanks for the response, I really appreciate it.

 

[RichardSM]

It defiantly has dirt on the sensor. As for the optical lens flare, I would use a lens hood while shooting outside in the bright sun.

Could it be that most of you on this site are overthinking this issue with the lens? flare!

 

[Tom Axford]

Huh, as you and others point out that sure looks like sensor dust. But you say you shot at F/2.0? Would usually not expect to see dust at that aperture.

Are you certain the lens was set to F/2 for these shots? The exposure seems to imply something more like F/8 (you have 1/3200 shutter speed at ISO 400 in daylight) but that's a coarse estimate. And doesn't seem like enough out of focus blur for F/2 on an APS-C, but again easy to get fooled here.

I presume you've tested with a different lens stopped down to F/16 or so to check that there isn't any sensor dust?

As to the flare that is indeed pretty bad but if their is a hazy lens element that could be expected.

Hey Ken,

I shot wide open and tried to shoot near close focus. I noticed on a few other photos that the dust particles only show up when the lens flares heavily and would disappear when there would be no flares.

You still need to check with the lens at f/16 or f/22 as Ken suggested. If it is sensor dust, as is almost certainly the case, it will show up at very small apertures (large f-number) without the flare being necessary. Its best to photograph something quite plain, such as a clear sky. You don't even need to focus the lens. Indeed, it's best to have the lens completely out of focus for the test!

Try it!

 

[sybersitizen]

... Aperture: F2

I don't think sensor dust would look like that at f/2 on APS-C.

Could be dust and other anomalies on or in the lens.

 

[Tom Axford]

... Aperture: F2

I don't think sensor dust would look like that at f/2 on APS-C.

You have ignored what he said about the spots occurring only if the flare was present. Flare indicates that the sun was shining directly into the lens. Its possible that a specular reflection from inside the camera body will produce the flare. It may be effectively coming from one small source and it will then produce exactly the same effect as having a very small aperture.

Could be dust and other anomalies on or in the lens.

Such dust in the lens would be so far out of focus as to not be visible in the image.

 

[sybersitizen]

... Aperture: F2

I don't think sensor dust would look like that at f/2 on APS-C.

You have ignored what he said about the spots occurring only if the flare was present. Flare indicates that the sun was shining directly into the lens. Its possible that a specular reflection from inside the camera body will produce the flare. It may be effectively coming from one small source and it will then produce exactly the same effect as having a very small aperture.

I'm not ignoring anything. You're proposing a possibility, but you don't seem to be saying you have seen sensor dust look like that at f/2 on APS-C under some conditions. Have you?

Could be dust and other anomalies on or in the lens.

Such dust in the lens would be so far out of focus as to not be visible in the image.

That's true in many cases but false as a general statement. I have seen personal results that show similar anomalies, and they were caused by the lenses.

Anyway, if the OP cleans his sensor thoroughly and the problem goes away, then we'll know you're right.

 

[Tom Axford]

... Aperture: F2

I don't think sensor dust would look like that at f/2 on APS-C.

You have ignored what he said about the spots occurring only if the flare was present. Flare indicates that the sun was shining directly into the lens. Its possible that a specular reflection from inside the camera body will produce the flare. It may be effectively coming from one small source and it will then produce exactly the same effect as having a very small aperture.

I'm not ignoring anything. You're proposing a possibility, but you don't seem to be saying you have seen sensor dust look like that at f/2 on APS-C under some conditions. Have you?

No, I haven't, but I am inclined to believe what the OP says - that the spots occur when the flare occurs and not if the flare doesn't occur. This clearly suggests that the light producing the flare also produces the spots. That is also consistent with the observation that those spots move slightly as the flare moves (compare his different images). It is all consistent with having a small source of light somewhere in the lens body or camera body that is generating the flare.

Could be dust and other anomalies on or in the lens.

Such dust in the lens would be so far out of focus as to not be visible in the image.

That's true in many cases but false as a general statement. I have seen personal results that show similar anomalies, and they were caused by the lenses.

The OPs spots are caused by the lens in the sense that using a different lens may not produce the same flare and hence not produce the spots. Are you completely sure this wasn't the case with your results?

Anyway, if the OP cleans his sensor thoroughly and the problem goes away, then we'll know you're right.

 

[kenw]

No, I haven't, but I am inclined to believe what the OP says - that the spots occur when the flare occurs and not if the flare doesn't occur. This clearly suggests that the light producing the flare also produces the spots. That is also consistent with the observation that those spots move slightly as the flare moves (compare his different images). It is all consistent with having a small source of light somewhere in the lens body or camera body that is generating the flare.

This is a very good working theory. I hadn't noticed the spots moved. Looking closely at them now some interesting observations:

1. IBIS wasn't on according to EXIF so that's not a factor.

2. The spots move relative to each other. Mostly they move up/down as a group but if you look at the spots on the left and right sides of the image you can see they also move inward/outward from the center of the image. So indeed like a fixed pattern of dust with a moving specular source illuminating them.

3. You can see the image from the lens still showing behind the large piece of dust. This seems to indicate the dust is just shielding the flare and not having much impact on the image forming light (as we'd expect it not to at F/2).

To the OP. Best guess you have two problems:

One is dust on the sensor. You should be able to use another lens at a very small aperture (F/22, F/32 - small as you can get) to likely see the largest piece of dust. Do that test.

Second is an internal specular reflection, most likely from the adapter for the lens. This is easy to check. With the lens mounted on the adapter hold it up to your eye with your eye about the right distance for the sensor. Using a flashlight or other bright flaring source in a dark room point the lens around in different directions. Likely at some angles you will see a bright specular reflection coming from some part of the adapter. If your eye sees it the sensor does to - that's the source of your horrible flare. Do something to make it go away (matte paint, flocking, whatever).

--
Ken W
See profile for equipment list

 

[sybersitizen]

... Aperture: F2

I don't think sensor dust would look like that at f/2 on APS-C.

You have ignored what he said about the spots occurring only if the flare was present. Flare indicates that the sun was shining directly into the lens. Its possible that a specular reflection from inside the camera body will produce the flare. It may be effectively coming from one small source and it will then produce exactly the same effect as having a very small aperture.

I'm not ignoring anything. You're proposing a possibility, but you don't seem to be saying you have seen sensor dust look like that at f/2 on APS-C under some conditions. Have you?

No, I haven't, but I am inclined to believe what the OP says - that the spots occur when the flare occurs and not if the flare doesn't occur. This clearly suggests that the light producing the flare also produces the spots. That is also consistent with the observation that those spots move slightly as the flare moves (compare his different images). It is all consistent with having a small source of light somewhere in the lens body or camera body that is generating the flare.

Could be dust and other anomalies on or in the lens.

Such dust in the lens would be so far out of focus as to not be visible in the image.

That's true in many cases but false as a general statement. I have seen personal results that show similar anomalies, and they were caused by the lenses.

The OPs spots are caused by the lens in the sense that using a different lens may not produce the same flare and hence not produce the spots. Are you completely sure this wasn't the case with your results?

I'm not completely sure because I didn't keep all of them. However, right now I can closely duplicate the sort of anomalies we're seeing in the OP's examples, and they are indeed caused by things on the APS-C sensor, not on or in the lens. So I withdraw my comment about stuff in the lens. But my spots are nearly invisible at f/2, so I presume any reflection-causing flare generated by my setup is quite different from that of the OP's setup.

Anyway, if the OP cleans his sensor thoroughly and the problem goes away, then we'll know you're right.

 

[mdmarqphoto]

Did anyone else notice that the larger item appears to be made up of many the single spots? The single spots have a light center, then a dark ring, then a light ring. Looking at the candy cane shaped spot, you can see the same circles creating it.

 

[bclaff]

It's unclear where exact those artifacts originate but it's definitely not "dust" on the sensor (cover glass); that would show in a consistent place and is very unlikely to show at f/2

 

[sybersitizen]

It's unclear where exact those artifacts originate but it's definitely not "dust" on the sensor (cover glass); that would show in a consistent place

We've been over that earlier in the thread. Dust on the top surface of the sensor sandwich can indeed appear to move - when focal length changes, for example.

and is very unlikely to show at f/2

We've been over that earlier in the thread as well. The hypothesis is that the illumination for those artifacts is coming from a point source reflection originating inside the lens, not the actual aperture, and the point source moves depending on the position of the external light source.

 

[bclaff]

It's unclear where exact those artifacts originate but it's definitely not "dust" on the sensor (cover glass); that would show in a consistent place

We've been over that earlier in the thread. Dust on the top surface of the sensor sandwich can indeed appear to move - when focal length changes, for example.

I don't believe this. The cover glass is attached to the sensor not something seprate.

and is very unlikely to show at f/2

We've been over that earlier in the thread as well. The hypothesis is that the illumination for those artifacts is coming from a point source reflection originating inside the lens, not the actual aperture, and the point source moves depending on the position of the external light source.

For it to be on the cover glass the cone of light has to be very narrow which won't happen at f/2

 

[jerry1]

Hi,

I took some photos with lens flares to see how the coatings perform on this lens I purchased. I really love the colors but I'm noticing some artifacts when the lens flares. I'm thinking the very prominent ones that are squigly look like dust. The ones that are dots also seem like small speckles of dust. Also there is a small amount of haze near the rear element. Would that contribute to these artifacts?

Camera: Fuji XT2

Lens: Olympus OM Zuiko 40mm F2

Aperture: F2

Shutter speed and ISO are in the metadata on the photo

Thanks,

Mike



Picture 1 (artifacts not pointed out)



Picture 1 (with artifacts not pointed out with red arrows)



Picture 2 (artifacts not pointed out)



Picture 2 (with artifacts not pointed out with red arrows)

Did you shoot raw and did you develop in Lightroom? I don't have a Fuji but have heard that Lightroom can cause funny things with Fuji raw files. If you do a search on Fuji raw and Lightroom you will probably find some reading that may help you. Good luck.