The orb zone is an area in front of a camera where object highlights appear as orbs. Objects such as bits of dust, insects, water droplets, and so on, all form orbs. This page is concerned with illustrating some of the properties of the orb zone through video. It does not go into details of the theory which is discussed here. And there is an orb FAQ here.
Orb zone in theory
The orb zone is shown in the diagram, right. The following discussion refers only to the appearance of small airborne objects, like particles of dust, water droplets and insects which produce orbs when they appear on the zone. Larger objects will, when in the orb zone, not look like orbs.
The key for the diagram is:
- F flash
- L camera lens
- C area too close to camera for any small object to be visible at all
- Z area where objects are out of focus and strongly illuminated by the flash
- O area where objects are out of focus but not strongly illuminated by the flash as they are too far away from it
- I where all objects are in focus and not strongly illuminated by the flash as they are too far away from it.
- Shaded area: The orb zone is the area where objects are both out of focus and strongly illuminated so that they appear as orbs.
Orb zone explored
To illustrate how the orb zone works in practice here, a slightly different set up was used, in conjunction with a video camera, as shown in the diagram below. This alternative layout makes it easier to see what is going on in and outside the zone. For instance, a torch is used to provide a continuous illumination source so that orbs can be observed moving around. Real dust was used to produce the orbs for these videos!
Some orbs appear to 'pop' out of existence. This can be seen in the following video: here
Commentary on 'popping' video: This video shows orbs moving around and sometimes apparently 'popping' out of existence entirely. This happens to orbs that grow larger, which indicates that they are approaching the camera. As they get closer to the camera they move out of the area illuminated by the torch (see diagram above). In fact, they leave the orb zone! As a result they vanish. Because the orbs grow larger before they vanish, it appears as if they burst!
The 'popping' happens quickly because the edge of the area that is strongly illuminated is sharply delineated. The orb grows larger as it approaches the camera because it is going further and further out of focus. It also tends to fade as it grows. There is a particularly good example of the 'popping orb' near the end of the video.
Dust turning into orbs
In-focus dust particles are not usually seen in orb photos because they are too far away from the camera flash to show up (area 'I' in the diagram, at the top of this page). However, with the torch setup used here, dust CAN be seen when in focus because it is illuminated from the side (see here), instead of from the camera. Thus dust is just as strongly illuminated whether it is in or outside the orb zone. So it is possible to see dust particles become orbs as they drift into the orb zone. This can be seen in the following video: here
When the dust is in focus in the video it mainly appears as moving bright lines or streaks, rather than dots. This is because the dust is moving relatively quickly and the dots are motion-blurred to become bright streaks. Many of these dust particles turn into orbs as they move (and some 'pop' - see above). Just before they turn into orbs, some of the dust particles turn into the more obvious dots you might expect to see. That's because most of the particles swing upwards as they approach the torch. As they do so, their motion-blur disappears because we are watching them approaching from above. Also, this upward motion brings them into the orb zone which is why they then become orbs. If you follow individual dust particles in the slow motion sections you can see this happen.
The photo (above right) is a grab from the video. You can see the dust particles as motion-blurred light streaks going towards the torch on the right. Near the torch you can see the ones that have already arrived and turned into orbs. Notice how the orbs start out white when they are small and become blue as they expand. The colour probably comes from a blue tinge in the torch light. You can see hints of blue in the torch itself in the photo here.
House dust is mostly grey (see here for comment on this), as indeed are most orbs. From informal experiments at ASSAP it appears that orbs mostly derive their colour from their source of illumination. You can only see orbs because they are reflecting light, so that makes sense. In the videos here, most of the orbs have a distinct blue tinge. That is probably because there is a blue tinge to the torch light used to illuminate them. There were, however, a tiny number of differently coloured orbs seen.
The photo (right) is a grab shot from one of the videos used in producing this page. The linear object, top right, is the torch which has a similar blue colour to most of the orbs in view. However, in addition to the blue orbs, there is one that looks yellowish and another reddish. The most obvious explanation for these unusually coloured orbs is that these particular dust particles are predominantly yellow or red. Blue is quite a common colour for orbs.
As it happens there is good evidence for the presence of a few such highly coloured dust particles at the time. The background of the videos consists of rough paper where lots of the dust particles accumulated during the making of the videos. Looking at the paper after the experiments, there was lots of dust visible, much of it the expected grey colour. But there were one or two more highly coloured particles present too.
Here is a photo (right) showing one such red dust particle. It might look like the surface of the moon but it is just rough paper. It is covered in bits of dust but most are invisible because they blend in with the background. This red dust particle stands out and would certainly explain a red orb. In fact, you can see some other dust particles in this photo if you look carefully. They appear as irregular whitish grains, barely visible, lying on the rough surface.
Orb group morphs into dust fibre
Sometimes several orbs appear together in a close overlapping group. When such a tight group shows up in a still photo it can give the appearance of one fast moving orb. This video (here) shows how such a group happens. You see a torch with the far edge in focus but the nearer one not. Dust is floating around strongly illuminated. When they are out of focus, because they're too close to the camera (and inside the orb zone), dust particles appear as orbs.
Later, as the group of orbs drift away, they leave the orb zone, come into focus and are revealed as a single large dust particle. It is a fibre (pic right), a typical component of household dust. Because the fibre is drifting directly away from the camera, it is not motion-blurred into a light trail.
This video illustrates how orbs are not simply out of focus objects, they are out of focus highlights ON objects. This is why one fibre of dust becomes at least three overlapping orbs. However, the vast majority of dust orbs seen are singletons. That's because most dust particles are much smaller than the one shown here. They are so small that they only contain one highlight! Large bits of dust, like the one in the video, rarely form orbs because they quickly fall to the floor.
Another interesting thing to note is that the dust fibre is rotating. This means that the highlights shift around as different surfaces of the object are presented to the camera. In the video, the number of orbs in the group actually changes and they alter relative position, all due to the rotation of the dust fibre. Though dust rarely produces groups of orbs like this, insects commonly do because they are larger and generally have many highlights. In the video, the dust fibre finally vanishes because it leaves the orb zone. Though still in focus, it is no longer strongly illuminated by the torch.
In the second grab shot from the video (above right) the overlapping orbs caused by the individual highlights on the large dust fibre can be clearly seen. Though such an orb group might initially suggest a single orb moving quickly, that would produce a light trail with straight edges rather than the overlapping circles seen here.
This video (here) appears to show two orbs colliding. The reason for thinking that they collide, rather than simply pass close to each other, is that one of them goes off in a radically different direction after their encounter. Both orbs are in the middle of the frame. One (white) orb appears to be moving diagonally upwards from left to right. It continues on that track afterwards! The other (bluish) orb is going roughly horizontally, from left to right, and then goes vertically downwards after the encounter. At least that's what appears to happen, assuming the orbs don't somehow change colour during their encounter! After the apparent collision, both orbs come into focus ('de-orb') and reveal themselves to be dust fibres. The fact that they both come into focus at the same time shows they are at the same distance from the camera, increasing the likelihood that it is a real collision.
In the first photo (above right) you can see the orbs approaching each other. Notice how each 'orb' looks fuzzy. This is because they are actually both tight groups of overlapping orbs, indicating that the objects causing them both have multiple highlights. In the second photo (right) the orbs have apparently collided and appear as one single orb, brighter than both of its constituents.
In the third photo (below right) the two orbs are travelling apart following the apparent collision. The white orb is continuing on its upward journey. The blue one has apparently been diverted downwards. Both objects have 'de-orbed', as they are now in focus, and are revealed to be linear dust fibres. The fact that they both come into focus shows that they are each moving away from the camera. In fact, the orbs were already getting smaller before the collision, suggesting that they were moving away from the camera even then.
These orbs are, of course, the out of focus highlights of bits of dust. As we can see, these particular dust particles are fibres and large by the standards of domestic dust (explaining why they appeared as overlapping orbs before the encounter). This makes a physical collision more likely than it would be for typical dust particles (and typical orbs) which are significantly smaller. Given that the white orb continued more or less unaffected, it is probably rather heavier than the blue orb. Given that these two bits of dust are large, by normal standards, it is likely that orb collisions are quite rare.
Measuring the orb zone
The size of the orb zone determines how many orbs there are likely to occur in a photo, if any. For most photos, there will be no orbs at all. Even when taking flash photos using a camera with a physically small sensor, orbs only occur infrequently. The best chance of getting orbs is when the orb zone is large and there is plenty of dust floating around.
The size of the orb zone varies according to a number of variables. These vary according to camera model, lens used, flash unit model, distance of photo subject, reflectivity of dust (or water droplets, insects etc) and so on. To get an idea of the size of the orb zone it is, therefore, easier to measure it than work it out from theory.
In the photos above metal screws were used to illustrate where the orb zone is. In the left photo all three screws are out of focus, their shape being made up of orbs. In the middle photo the furthest screw is now in focus. The screws were not moved between shots nor was the camera but the orb zone changed. The difference is that the camera was zoomed between the two shots (by a factor of around 1.9) and the f-number altered (from 4.5 to 5.1 = not a big change). Zooming alters the focal length. The orb zone was reduced in size towards the camera with the furthest screw going out of it.
It should be pointed out that dust has a lower reflectivity than metal so the orb zone for dust would not be as big. In the right-most photo dust was deliberately released into the area for the flash, resulting in an orb in front of the word 'spotlight'. The dust orb was much fainter the orbs on the metal screws. The actual orb zone for metal in this test was up to some 25 cm from the camera! For dust it would be smaller than this.
Looking at a more realistic example, here is a tailed orb (right). It is actually a raindrop photographed at night using flash. The tail is caused by the motion of a falling raindrop in the orb zone. The reason it appears to be going upwards is explained here. Because of the motion of the orb / raindrop, it should be possible to work out its distance from the camera.
It can only be a rough calculation because of the assumptions that need to be made. Let's assume. for instance, that the raindrop is falling at around 5m/s, though it can vary between 1 and 9 m/s depending on the size of the drop. Let's further assume that the flash duration was around 2/1000 s. A typical flash lasts around 1/1000 s but this one was extended as the tail shows (see earlier link to explain this). This means the raindrop should fall around 1 cm through the air during the flash.
I set the same camera to the same focal length as used during the tailed orb photo. I then placed a ruler at various measured distances from the camera taking its photo each time. I wanted to see what distance would make 1 cm occupy the same percentage of the frame as the tailed orb did in the original full size photo (the picture here is a cropped version).
The answer was around 15 cm. So, though the orb / raindrop looks as though it is just in front of a bush, which was 2 or 3 metres from the camera, it was actually only around 15 cm away. This gives some idea of where the orb zone, for water droplets at least, was for this camera on this particular occasion. The zone itself would have extended some distance around that 15 cm. Note once again that this is only an approximate figure. Interestingly, the 15 cm for the tailed orb is not wildly different to the 25 cm for the metal screws suggesting that the orb zone may sometimes extend out to 30 cm or so from the camera, at least for objects like water droplets.
Orbs with motion-blurred background
Occasionally orb photos show a motion-blurred background. There is an example here (right). Behind the bright orb the background consists of the leaves of a bush. However, these are difficult to see because they are blurred by camera shake. The leaves appear as streaks, all aligned in the same direction. This is typical of a photo affected by camera shake. The photo has been brightened slightly and had its contrast increased a little to show the dark leaves better.
So why is the orb not affected by the motion blur? The orb is an out of focus bit of dust close to the camera. It was only visible because of the flash, which lasted about 1/1000s. However, the camera shutter was open for 1/60s. The bush in the background was too far away to be illuminated by the flash being lit by daylight instead. The camera shake was enough to blur the background during 1/60s but not enough to affect the orb in 1/1000s.
This situation occurs when a flash is used with dust near the camera lens but the background is distant and well illuminated by some other source, like daylight or artificial lighting. So why doesn't the camera just use a shutter speed of 1/1000s with flash? This 'flash synchronisation speed', which is typically much linger than 1/1000s, is explained here.
The fact that the orb is sharp while the background is motion-blurred is, as explained above, easily explained by orb zone theory. Any rival theory would need to explain this phenomenon which might be difficult!
It has been suggested that orbs cannot be dust because dust particles are too small for ordinary cameras to photograph. Though dust is omnipresent in the air, we do not normally see it because the particles are too small and have low reflectivity. But it is easily possible to see dust in a shaft of sunlight with the naked eye. So can these same dust particles also be photographed? When taking an orb photo, the camera flash provides the brilliant light source that makes dust visible. To take a photo of dust IN FOCUS (not appearing as an orb) it is easier to use a torch which acts like a shaft of sunlight or camera flash.
In the first photo (above left) there is a particle of dust illuminated by a torch. An uncropped version of the photo (above right) shows the dust particle floating in front of the torch that is illuminating it. It is clear that the dust particle is not an orb! It appears to be a fibre of some kind. A lot of household dust consists of such fibres, shed by furniture, clothing and paper. This one might come from paper!
The next photo is more typical, showing a long fibre which is also clearly not an orb. It was photographed in the same way at the dust fibre above. An ordinary camera was used to take these photos used at normal settings - nothing unusual. The dust arrived by itself, it was not generated by shaking or blowing any dusty object.
Such dust particles turned up in ones or twos, in an ordinary indoors domestic environment, every few seconds or so. It is likely that only dust particles of this size, or larger, produce orbs. There are many more dust particles in the air but they are too small to be photographed by ordinary camera equipment. This would explain why orbs are not very common. To be seen as orbs, dust particles also need to be in the camera's orb zone.
When the focus of the camera was shifted to a point further away, it put these dust illuminated particles into the camera's orb zone. The photo (left) shows the result - an orb. You can still see the torch (top centre) which is now too close to be in focus. This confirms the suggestion above that particles which appear in torch light are of the correct size to be photographed as orbs. The dust particles were also visible to the naked eye while these photographs were being taken. So, it is clear from these photographs that an ordinary camera can, with the help of a torch, photograph some larger particles of household dust that are floating in the air, without any deliberately produced dust clouds. Further, these dust particles become orbs when they are inside the camera's orb zone.
There is a video here showing dust illuminated by a torch in and out of focus. The dust starts in focus because it is at the same distance from the camera as the torch. Then the cameras focus shifts to a pen some 0.9m away. In doing so, the dust particles go out of focus and become orbs. In the first still from the video here (left) the torch is in focus and dust as well. Some of the dust particles appear as light streaks because they are moving primarily sideways, as opposed to towards or away from the camera.
In the second still (right) the torch is out of focus and the dust has turned into circular orbs. In the video the visible dust and orbs are confined to the area just in front of the torch which is highly illuminated. Both dust particles and orbs vanish when they exit this highly illuminated area. The orbs get larger and fainter towards the end of the video. That's because the focus is still shifting to make the pen sharp. In doing so, it moves the orb zone further away from the camera putting the dust particles more out of focus.
This video shows how an ordinary camera using ordinary settings can photograph dust both in and out of focus when they are highly illuminated. In still photos the light source is usually the camera's flash. This setup does not produce in focus dust particles because they are too far away from the flash to be visible. By using a torch it is possible to show dust both in and out of focus, to illustrate how orbs are formed.
Why do orb numbers vary so much?
Why do many photographers never get orbs while others get many? And why do the number of orbs seen vary so much between photographs, even those taken just seconds apart? It is obviously related to how many objects that can produce orbs, like dust particles, insects, rain droplets and so on, are present. But the other factor, just as important, is the size of the orb zone which can vary hugely between consecutive photographs. That's because the factors affecting the orb zone can change a lot between each shot, especially with automatic cameras (as nearly all are nowadays).
It is theoretically possible to calculate the size of an orb zone for a particular camera but in practice it is very difficult. The zone size depends on:
- the depth of field of lens in use
- the brightness and duration of the flash
- the distance and reflectivity of any possible orb zone causing particles present
- the orb causing particles size (needs to be above a minimum)
- background shade / colour
The first two factors are not too difficult to calculate. Depth of field depends on the focal length and f-number of the lens and the distance of the subject from the camera. The brightness of the flash depends on its guide number. However, the amount of illumination a flash unit gives also depends on flash duration. A camera will detect how much light is being reflected during a flash and if it is insufficient it will extend the time the flash goes on for. Typical flash durations are around 1/1000s bit they can last several times as long.
Then there are the orb causing objects (OCOs) themselves. These vary in reflectivity (how much light they reflect). Effectively, more reflective objects have a larger orb zone. Whether they are bright enough to be seen as orbs also depends on their distance from the camera lens AND from the flash unit. The OCOs need to be a minimum size for a camera to record them, whether in or out of focus. Experiments suggest that if you can see a particle of dust in a shaft of sunlight then it can be photographed and produce an orb. Such objects are on the large size for airborne dust and probably only take to the air indoors due to physical disturbances, like people moving around. The number of such dust particles airborne at any one time will therefore vary a lot.
So the number of orbs appearing on photographs will vary a lot. Someone using a camera with a physically larger sensor (and so a smaller depth of field) will seldom, if ever get orbs. Though you can get orbs without a flash unit, someone who never uses flash will, again, seldom if ever get orbs. Someone whose camera has a physically small sensor, who uses flash a lot, may well get orbs from time to time. But even then it can vary a lot between shots. One thing that matters a lot, for instance, is subject distance. For a distant subject, the depth of field will be large and the flash duration long. Both of these factors will make getting orbs more likely compared to a close up. Since someone might take a photo of a nearby subject followed by a distant one immediately afterwards, this might explain why there are lots of orbs in one photo and none in the other. And the camera will make adjustments that affect the orb zone size automatically between shots without the photographer being aware of it.
So, in summary, the number of orbs seen in photographs will depend on many different factors, some of which can vary from second to second. These include, physical sensor size, distance of subject, focal length of lens, darkness of background, physical disturbance in the area and so on. Anyone who wants to see orbs a lot could use these theoretical factors to increase their chances or may simply discover them by trial and error.
© Maurice Townsend 2013, 2014, 2016, 2017