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When taking a photo towards the sun, I found there is a green dot on the photo. I'm pretty sure this is caused by the sun, the camera has no problem. Question: what is the cause of this green dot? why green and what is the size of it?

Camera information:

Rear camera     Samsung ISOCELL [2][3]
1/2.6 -inch 16 MP BSI sensor
ƒ/2.2 aperture
31 mm focal length

enter image description here

ps: is it bad for camera when taking photos facing very strong light?

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  • $\begingroup$ The left-bottom position? Just a guess, this is an image of the sun, being generated some-how in a certain layer of lens or filter or chemical coating on lens. That is probably very faint in normal-light, but clear in very-bright light. You could check taking image of a dimmer source like tube-light, etc of different shapes and from different angle, and could see is there any change in shape and position of green dot. Green colour is probably due to any characteristics of lens or layer material. $\endgroup$
    – user115953
    Commented Jul 27, 2016 at 18:10

2 Answers 2

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This is probably a better question for photography, not physics.

I believe that green dot is a lens flare. It's the effect of the sunlight reflecting off of the optics that, in an ideal world, would not reflect at all. Its position and size are based off the angle between you and the sun and the particular position of the elements in your lens.

As for whether its bad for cameras, you can damage your CCD that way. It is recommended that you avoid shooting directly into the sun. However, sometimes you can get away with it, especially near sunset where the brightness of the sun is at a minimum.

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    $\begingroup$ Lens flare used to be a very common abuse of Photoshop theoatmeal.com/comics/design_hell $\endgroup$ Commented Jul 27, 2016 at 9:42
  • $\begingroup$ My digital camera shows violet or pink colored patches and lines if mistakenly shot at very-bright source like a shining cloud or lake. $\endgroup$
    – user115953
    Commented Jul 27, 2016 at 18:21
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The lens elements in a camera contains anti-reflection coatings (thin films). Although they are intended to remove all internal reflections, they are not perfect. Their effectiveness generally depends on incident angle and wavelength. When you photograph an intense source of light, such as the sun, the little bit of light that is reflected is enough to show up in the photograph and the color is an indication of the wavelength dependence of the particular coating.

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  • $\begingroup$ You mean all light other than green is reflected by the lens, therefore, the dot is green? Therefore, the thickness of the coating is $\lambda_{green}/4$. $\endgroup$ Commented Jul 27, 2016 at 17:07
  • $\begingroup$ And what about the dot size, can you get from the camera info? $\endgroup$ Commented Jul 27, 2016 at 17:08
  • $\begingroup$ Diagram (Scroll down the page). $\endgroup$ Commented Jul 27, 2016 at 22:36
  • $\begingroup$ Since the green dot appears in the image and is caused by internal reflections in the lens system, it would need to have been reflected at least twice. Since the spot itself is green the light that has been reflected must have included the green wavelengths. AR coatings generally consist of multiple layers to make them broad band, as a result one cannot really make a statement about their thickness based on the reflected color. As for the size, it would also be a rather difficult thing to predict, due to the modified lens system, which now includes the reflections from curved surfaces. $\endgroup$ Commented Jul 29, 2016 at 4:34

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