Photography Colour Management
Whole books have been written on the topic of
colour management, so we shall only attempt to
provide a basic outline for you here. If you would
like to know more about this subject, please feel
free to contact
us.
Overview
Colour Management is a system that attempts to
provide an accurate representation of colour across
a wide variety of devices, such as monitors, digital
printers, offset printers, scanners, projectors,
and cameras. In effect, any device that either
captures or displays colour.
As a system, colour management is neither foolproof
nor complete, due to the great complexity with
which colour is determined by human eyesight and
our brains. However in the majority of circumstances,
and with foreknowledge of where the gaps in the
system are, colour management is an extremely
useful tool, and a necessary part of any desire
to create quality images.
Why do we need Colour Management?
Before digital, when dealing with film, we always
had a physical representation of colour (the film
itself) that we were able to compare output results
against.
With a digital workflow, from capture to final
output and display, colours are described purely
with numbers. These numbers tell a particular
device such as a monitor or printer, how to display
a certain colour. If a single set of number were
provided to a series of devices, the real colour
that is displayed to our eyes can be subtly affected
for example, by variations in the electronics,
dyes, or phosphors in a monitor, or the variations
in ink, type of paper, or brand of printer being
used. These variations can and do occur even between
devices of the same brand and model number.
These variations also change over time as parts
wear out, phosphors or inks age, and variations
in manufacturing occur. Additionally, the variations
can multiply as files are passed through a series
of devices, each with their own bias.
Colour Management is the system which allows
these variations to be normalised so that colours
will look the same (or very similar) across multiple
devices in multiple locations.
How is Colour Management important to
you?
If you are providing instructions as to the desired
treatment of a particular image, it is vital that
both yourself and the photographer / graphic designer
/ printer are on the same playing field (so to
speak), by having properly calibrated monitors
and profiles for output devices.
Monitor calibration is at the centre of colour
management, and it ensures that the image you
are reviewing on your screen is the same as the
one the photographer or designer expected you
to see. If for example, you were viewing an image
on an un-calibrated monitor that was biased towards
blue, you would see neutral colours as being more
blue than they should appear. If changes were made to this
image based upon its appearance on this monitor,
it would have potential negative consequences
in later output.
Device Profiling & Calibration
Profiling and calibration are flipsides to the
same coin.
Calibration alters the physical characteristics
of a device to alter the actual colours it is
outputting. For example, if you had a single set
of numbers that represented a mid-grey, and output
this colour to a monitor (say the blue biased
monitor from the above example), the mid-grey
would actually appear somewhat blue. It is possible
to adjust the monitor settings so that the blue
bias was removed and the grey is actually displayed
as grey.
Profiling works from the opposite side. Profiles
are created by sending a known set of colour numbers
to a device, and measuring how the device outputs
the colours. The profiles then act like filters
between the computer and the device, and alter
the colour numbers in such a way that the correct
colours are output. For example, with our blue
biased monitor, the grey would be measured with
more blue. A profile created would then change
the original numbers so that the blue was counteracted
and cancelled, with the result once again that
grey is actually displayed as grey onscreen.
Most colour management is a combination of both
calibration and profiling.
A Little Bit of Science - Colourspace,
Gamut, & Conversions
Whilst the human eye is capable of recognising
a very large range of colours, there are as yet
no devices with the capacity to reproduce all
those colours, even if it is possible to represent
them numerically. Moreso, there is a difference
in the way colours are produced when viewed on
a monitor for instance (where light travels from
the monitor to your eyes), to printed materials
(where external illumination is required, and
that light bounces off the surface of the printed
material and back to your eyes).
There are two general ways in which colour numbers
are presented (actually there are more, but we
shall only go into two here). These are called
Colourspaces. The two main colourspaces are RGB
(short for Red Green Blue), and CMYK (short for
Cyan Magenta Yellow blacK). As with the example
above, RGB is normally used in situations where
the light travel directly to your eyes, as in
from a monitor. CMYK is used where external illumination
is needed for printed materials, as the CMYK represent
amounts of those coloured ink put down onto paper.
Each of these colourspaces has the capacity to
represent colours that the other cannot. The range
of colours able to be represented by a particular
colourspace is called its "Colour Gamut".
When converting from one to the other (which in
most cases will happen when producing graphic
artwork from a digital file), colour management systems also tell
the devices how to deal with colours that fall
outside of the range, or "gamut".
Additional Factors Affecting Colour
A range of other factors can affect how colour
is viewed, and are some of the elements that must
be taken into consideration when highly accurate
colour is required.
The lighting conditions under which colours are
viewed can effect their appearance, as different
light sources impart their own colour bias to
any viewing situation. Additionally the physical
and chemical properties of some objects can cause
them to appear differently under various lighting
conditions. i.e. two objects that appear to be
the same colour under daylight will look different
under halogen lights.
When viewing critical colour on a monitor, it
is also important to note that your perception
of colours can be affected by any bright or colourful
background behind the monitor, as well as any
colourful background behind the viewer.
Finally, as colour perception is also an effect
of the human brain and eyesight, not all people
will view colours in the same way (take for instance
people who are colour blind). Colour Management
systems utilise the way in which the strong majority
of people perceive colour. Even in the cases where
people perceive colour differently than the norm,
there is still benefit gained through colour management
systems, though perhaps not to the same degree.
What We Can Offer
We use colour calibrated monitors and a colour
managed workflow. We offer monitor and printer
calibration services for businesses also wishing
to use a colour managed workflow.
If you would like to learn more about how colour
management may aid your business, please feel
free to contact us.
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