How does this change in lighting come from the camcorder?
That's a good one. Are there any more like this. Or is this unique?
I'll go ahead and give my explanation. If more like this are found I'll look at them.
If we assume my projector idea:
You hold a finger in front of the projector lens. The finger close to the projector lens creates a blurry area on the image projected on the glass. Where the blur meets the image on the glass, you get that dark area where you can still see some of the features of the image projected on the glass. Move your finger carefully, and you get a moving band of darkness on the object.
During this segment Yalcin periodically
also changes the aperture setting on the camcorder.
More detail:
What we see is a bright, focused image. The object is lit by a single light source. The top of the rounded object shows no details because of over exposure. On our left, a band of darkness starts moving across the object on our left. It moves until the center 2/3 of the object is obscured. It moves back to our left.
Note that in the area of darkness, details of the object can still be seen but they appear less sharply defined. That area of the image is darker, less contrasty and the image has poorer resolution.
If this image were steady, instead of characteristically jittery, I'd say this:
An object, very possibly a finger, was held close to the camcorder lens. I'm going to call it a finger.
The finger is too close for a telephoto lens to focus upon. It's distance is below the minimum focusing distance of the lens. It's night and the finger is not illuminated, so it's just a dark thing in the way of the light coming from the illuminated object. A silhouette.
Nevertheless it's an unfocused image. The unfocussed image is spread out over the focused image of the object on the sensor. Or part of it, really. Where the unfocused image of the finger and the focused image of the bright object meet, there's an area, not of total darkness, but where the two blend together.
The result: In that area we see a darker, less contrasty, lower resolution image of the the bright object. If you carefully move the finger, it looks like a dark band is moving across the object. If you perceive the object as self-illuminating, it looks like a light show on the surface of the object. Something like the chromatophores on a squid.
But... because the camera was unsteady, this finger in front of the lens scenario is impossible.
The finger in front of the projector lens is possible, and rather easy to do.