Lens Flares explained


Senior Member.
We're sometimes explaining "white dot" UFO sightings as lens flares. I came across a short explanation video for this phenomenon, to show the uninitiated:

Source: https://youtu.be/z_WRaTsGbVE?si=d_0lSIovsD3wTxX_

1) Lens flares are typically symmetrical to the optical axis, which means that when you draw a line from the flare through the center of the image, the source of the flare should be on that line, if the image has not been cropped.
2) Image stabilisation moves the image around stealthily, so on videos, the flare source can appear stable while the flare moves around with the camera. (In an unstabilized video, both would move symetrically.)

Please add examples!
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Pretty hard to miss what this one is...
internal reflections camera 2.jpg

My colloquial understanding of "flare" would lead me to expect something like a glare, so those with a knowing of cameras can verify if this is indeed lens flare, or some related reflective phenomenon. Other examples I have on file:
internal reflections camera ufos.jpg

(I think UFO of Interest channel on YouTube is the source for this, red and green lines showing symmetry are by me.)

internal reflections camera.jpg
internal reflections camera 6.jpg
Those look mostly like "sensor reflections" where the strong light source reflects off the sensor back into the lens then back to the sensor again.

The terminology for optical/camera artefacts gets a bit mixed up and cross use is common.

Glare/flare/Bloom etc
Thanks jarlmai! "Internal reflections" is the term I'd used discussing them in other venues, sounds like that might be closer to the mark than "lens flare." Would I be correct in using this pic (not mine) as an example of lens flare, as opposed to sensor reflections in my previous post?

The terminology for optical/camera artefacts gets a bit mixed up and cross use is common.

Glare/flare/Bloom etc
Glare and bloom refer to a bright object appearing bigger than it is, hiding the object's true size and shape. (You can often see that on the objects causing the lens flares.) Bloom is technically something that happens inside the camera (and some would limit it to the sensor or film developing process itself), while glare is used when the cause is outside the camera, e.g. the atmosphere; though glare is often used regardless of the cause.

Lens flares, on the other hand, are located away from their original light source in the scene. (See the video in the OP.)
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