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What do you mean, 'orbs
aren't actually dust!'
This might seem like a
strange assertion, considering conventional wisdom -
including the contents of this website - but read on!
Dust usually doesn't look
like orbs!
In fact dust usually isn't
even round! A lot of dust are actually fibres. Orbs are caused by dust, but they are not
actually representations of dust particles or 'motes' as
many people believe.
Orbs are actually 'circles
of confusion' (CoCs). CoCs are out-of-focus points
of light caused by a reflection 'highlights' on
dust particles
How do highlights work?
Highlights are all around
us. You can see clusters of highlights on almost
any object. Look around you: the closest point to
you on most objects (when you have the light on) is
white.
You can see, below, the
highlight cluster caused by photographing this apple.
And this may well be how you see it with your naked eye,
too:
Because dust particles are
so small they usually only have 'one highlight' that is
reflected. It is this highlight, a pinprick of
light, that becomes out-of-focus and appears as an orb.
This helps to explain why the colour and shape of an
orbs is not the colour and shape of dust.
What are CoCs?
In photography, a CoC is the
smallest dot that a human eye can perceive in a photo.
When an object highlight is out of focus, this dot
expands to become a recognisable circle. In the case of
an out-of-focus dust particle caught in a flash, this
circle is seen as an orb. The CoC size is usually around
0.05mm can varies from camera to camera.
Because dust particles are
so small they usually only have one 'highlight' and thus
produce just one CoC - or orb. Larger objects have
more than one highlight and thus can appear to be made
up of a number of orbs:
Below is a good example of 'orbing'
of a normal object, from the ASSAP website. Notice
how you only see the bright highlights appear as orbs.
The darker areas produce no visible orbs.
Why is this important,
again?
The distinction of an orb
being "out of focus dust" and "a circle of confusion
resulting from a highlight on a dust particle" might
seem like a picky distinction in the greater scheme of
things but it isn't.
The fact that orbs are CoCs
affects the colour and shape of orbs. Some people
think coloured orbs are 'special' because they are not
dust coloured and that oddly shaped orbs are 'special'
because they are not the shape of dust.
In reality no orbs are the
shape or colour of dust. Orbs are the colour of
the light reflected and the shape of the aperture of the
camera!
Where the orbs-are-dust
theory falls down for many people is in explaining these
exceptional cases of 'odd looking' orbs. But by
understanding the role of CoCs we can understand why
these 'odd' orbs occur.
Learn more about CoCs:
CoCs are a complicated
subject which we have done justice to, but here are a
couple of websites where you can learn more:
Vanwalree on CoCs
Wikipedia on CoCs
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