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How to detect sensor burn in an image

Marion Muirhead , Sep 06, 2009; 11:07 a.m.

One evening I was out shooting Egrets and was excited about the opportunity to photograph an Egret in flight at close range. Usually the birds are too wary for this sort of opportunity, but a bird flew right in front of me, and a little voice in the back of my head said, "Don't go there" as the bird flew across the sun, but, I had read in my 40D manual that mirror lockup would be required to cause sensor damage, so I continued following the bird.
I was using a 400mm telephoto lens and as the bird crossed the sun the light was so intense that I felt a severe pain in my eye. My eye later became inflamed and was extremely red for a few days, and oddly I developed a swollen gland in my neck on the same side, which I still have a week later.
I began to notice that images taken later were fine if the background was dark, but if the background was sky a series of roundish gray spots would be visible. I tried cleaning the lens filter several times, but it hasn't made a difference.
Could this be sensor burn? If so, can anything be done for it?
Thank you

Responses


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Curtis Harkrider , Sep 06, 2009; 09:40 p.m.

Sensor damage is possible but unlikely since most sensors have overload protection. The roundish gray spots could be lens flare from the sun outside the field of view. You could take some shots against a blank white wall to see if the artifacts are still there. Another possibility is there is dust on the sensor or on the back of the lens. If you clean the back of the lens and the sensor window and you still see spots you might want to send your camera in for evaluation.

David Long , Sep 07, 2009; 06:58 a.m.

I think you should see an eye doctor. Worry about the camera later.

Marion Muirhead , Sep 07, 2009; 01:26 p.m.

Thanks for your replies!
The only other thing I can think of is condensation on the back of the lens or the sensor; I was out early the following morning and it was cold and dewy. (I only change lenses a few times a year and in a dust-free space.)
The spots in the images look like dust rather than dead pixels, and I think that they may have appeared a day later than immediately after the incident; also, the whited out area in the images of the Egret are on the right side of the image, whereas the spots appear at the top centre and upper right quadrant.
Thanks for your concern about my eye, David! I've had long-term problems mainly with the left eye, and I think it is eye strain from looking through the viewfinder. The pain was only for a fraction of a second, but I won't be taking that chance again. Better to lose tracking on the bird.
I'm going to check the back of the lens and sensor for dust.

Bill Tuthill , Sep 07, 2009; 03:23 p.m.

I have heard of this phenomenon (CCD damage from direct sun) but this dpreview forum post debunks the idea.

Marion Muirhead , Sep 07, 2009; 04:57 p.m.

Thank you for the link, Bill.
After many attempts, I managed to determine that dust had somehow gotten onto the lens. I never take the filter off, but it does loosen on its own while I'm hiking, so something must've gotten onto the threads and worked its way in--maybe a fibre from clothing.
Using a manual dust blower only moved the dust around, so I finally had to use compressed air.
I try to avoid that because it's possible for the liquid in the can to get onto the lens if you hold it too close to the glass. I don't know how harmful liquid nitrogen is to lens coatings, but it can't be good. I once managed to get some on the filter and wiped it off immediately, but wanted to avoid taking a risk with the lens, so I held the can about a foot away.

Thanks, all.

Steven F , Sep 08, 2009; 02:49 a.m.

Thanks for your concern about my eye, David! I've had long-term problems mainly with the left eye, and I think it is eye strain from looking through the viewfinder. The pain was only for a fraction of a second, but I won't be taking that chance again. Better to lose tracking on the bird.

It was not eye strain. Inflammation and redness are not cause by eye strain. Lenses concentrate the suns light in a smaller brighter spot which causes high temperature on the eye. What you had was a burn cause by the intense light. If you had looked at the sun a little longer it would have blinded you permanently. Go see a Doctor to insure the eye is healing properly. Never look at the sun or the moon through the viewfinder in the camera.

As to the camera, the sensor is somewhat more durable than your eye and was exposed to the sun for a very short time. It probably was not damaged. You would need to to have the sun in the same spot of the image for at least a second, probably much more, for the heat to fry the sensor. When live view is on the sun would be on the sensor for a much longer period of time.

I don't know how harmful liquid nitrogen is to lens coatings, but it can't be good.

Canned compressed air doesn't contain air. Nitrogen doesn't liquefy under high pressure and therefore it is never in canned air because the can would only supply a second or so of air. Canned air typically contains a hydrocarbon or hydrofluorocarbon. These are liquid under low pressure but are a gas in air. These compound can under the right condition briefly liquefy when they leave the can. They shouldn't cause any permanent damage to the glass of the lens. However compressed gases can bend and damage the delicate shutter curtains and reflex mirror mechanism in the camera which is why it is not recommended for cleaning the sensor.

Steven F , Sep 08, 2009; 03:01 a.m.

I have heard of this phenomenon (CCD damage from direct sun) but this dpreview forum post debunks the idea.

In one museum I visited I saw some equipment that was used 200 to 300 years ago in experiments. Basically it was noting more than one large lens with a metal target at the focus point. The lens was used to melt the metal or rock targets. It was very successful in doing this based on the used targets I saw.

For short exposures the sensor would be fine. However with a long exposure, which could be minutes with live view on and the camera on a tripod, the sensor can get hot enough to melt the circuits on it. If you put a film camera on a tripod and set it to bulb you can melt a hole in the film. The comment on DPreview is only valid if the exposure is short, which was typically the case before live view was available.

Curtis Harkrider , Sep 10, 2009; 02:06 a.m.

When you look through a camera viewfinder, you're looking at a ground glass screen which is at the focal point of the camera lens. The light that hits that screen is scattered by the ground glass, some of which makes it into your eye, but most of the light energy is scattered elsewhere. This is different than a telescope, in which there is no ground glass screen. With a telescope, all the light goes through a small part of the eyepiece, so you would be in big trouble if you looked at the sun through a telescope. If you notice, with a telescope your eye has to be in the proper place to see anything (the exit pupil of the system). With a camera viewfinder you can look through it any way you like and still see the image (exit pupil is much larger). While it's smart to avoid looking at the sun through the camera viewfinder, it's not nearly as dangerous as looking at the sun with a telescope or pointing a laser pointer at your eye.

Steven F , Sep 11, 2009; 01:50 a.m.

The light that hits that screen is scattered by the ground glass, some of which makes it into your eye, but most of the light energy is scattered elsewhere.

Some light is scattered, but not all. Additionally when you look at the sun through the view finder your eye isn't just seeing visible light. You also are hit with a large amount of IR light. if you have a fast lens on the camera the spot will be much more intense that the spot created with 5.6 lens. Also some cameras have brighter screens than others. Also the sun at sunset and sunrise is not as intense as it is at noon.

I was using a 400mm telephoto lens and as the bird crossed the sun the light was so intense that I felt a severe pain in my eye. My eye later became inflamed and was extremely red for a few days, and oddly I developed a swollen gland in my neck on the same side, which I still have a week later.


The fact that he instantly felt pain indicates injury. Inflamation and redness is another indication of injury. And all of that was with sun in the viewfinder only briefly. If the exposure was longer the injury would have been worse and possibly perminate. And speaking from personal experience the full moon under the right conditions can be much worse than a laser pointer. Fortunately I wasn't injured.


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