A few months ago I started noticing an unusual "artifact" (or so I thought it was) in some of the footage I captured.
What I noticed could be sumarized as a hot-spot on the video frame, which only shows under certain conditions and, for the most part it is almost unnoticeable (which made me believe I was convincing myself to see things that weren't really there), but other times it was definitely there:
(levels adjusted to help see the hot-spot)
At first I thought it could be some defect or damage on the video sensor, but I quickly discarded this hypothesis when I noticed the Hot-spot moved along the screen consistently when the Typhoon moved or yawed.
It kind of bugged me, but since it's rarely noticeable I soon forgot about it. However, I recently started noticing this "artifact" again on 2 different CGO3+ cameras, so I decided to figure out what was happening..
It turns out it has a very simple explanation and its extremely common, however as previously mentioned, for the most part it's almost unnoticeable unless certain conditions are met.
What we're watching is known as the Opposition Surge (aka Opposition effect, opposition spike or Seeliger effect). And yes, it is just what I was seeing: a bright glow or Hot-spot around the observers´ shadow.
The technical explanation is: the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer.. When looking in a direction directly away from the sun, shadows are hidden by the object casting them. The point opposite to the sun and the adjacent areas therefore appear brighter than elsewhere because they have more sunlit surfaces and less shadow. (source: Opposition Effect)
The only times you will get to see this interesting effect (on your aerial footage at least) is when you're looking directly away from the sun (hence at the aircraft's shadow) while flying over a rough surface; a uniform colored surface will make the effect more obvious.
This effect is nothing new and isn't exclusive to aerial imagery, (it is the cause for a full moon to be so much brighter than when its on any phase, it can also be seen from an airplane or during a regular day just by taking a picture at your camera's shadow)
Anyway, I decided to compile some clips where this effect is noticeable. Each clip is followed by an edited version with adjusted contrast to better notice the effect (it can be sometimes very very faint, but it is there after all)
Some of you must have already known about this, but I just wanted to share with you my recently acquired knowledge along with some real-life video examples.
It might be something worth considering when planning your aerial captures!
Greetings!
What I noticed could be sumarized as a hot-spot on the video frame, which only shows under certain conditions and, for the most part it is almost unnoticeable (which made me believe I was convincing myself to see things that weren't really there), but other times it was definitely there:
(levels adjusted to help see the hot-spot)
At first I thought it could be some defect or damage on the video sensor, but I quickly discarded this hypothesis when I noticed the Hot-spot moved along the screen consistently when the Typhoon moved or yawed.
It kind of bugged me, but since it's rarely noticeable I soon forgot about it. However, I recently started noticing this "artifact" again on 2 different CGO3+ cameras, so I decided to figure out what was happening..
It turns out it has a very simple explanation and its extremely common, however as previously mentioned, for the most part it's almost unnoticeable unless certain conditions are met.
What we're watching is known as the Opposition Surge (aka Opposition effect, opposition spike or Seeliger effect). And yes, it is just what I was seeing: a bright glow or Hot-spot around the observers´ shadow.
The technical explanation is: the brightening of a rough surface, or an object with many particles, when illuminated from directly behind the observer.. When looking in a direction directly away from the sun, shadows are hidden by the object casting them. The point opposite to the sun and the adjacent areas therefore appear brighter than elsewhere because they have more sunlit surfaces and less shadow. (source: Opposition Effect)
The only times you will get to see this interesting effect (on your aerial footage at least) is when you're looking directly away from the sun (hence at the aircraft's shadow) while flying over a rough surface; a uniform colored surface will make the effect more obvious.
This effect is nothing new and isn't exclusive to aerial imagery, (it is the cause for a full moon to be so much brighter than when its on any phase, it can also be seen from an airplane or during a regular day just by taking a picture at your camera's shadow)
Anyway, I decided to compile some clips where this effect is noticeable. Each clip is followed by an edited version with adjusted contrast to better notice the effect (it can be sometimes very very faint, but it is there after all)
Some of you must have already known about this, but I just wanted to share with you my recently acquired knowledge along with some real-life video examples.
It might be something worth considering when planning your aerial captures!
Greetings!
