Colour is a perception and not a property of an object!

It is important that you fully understand the concept of what colour is before measuring and communicating it.

 

Forget what you think you know about Colour, because Colour is not a constant property, it is something we perceive due to changes in light.

What we see is a reflection of light that is emitted off an object. Thus colour as we know it, is merely our perception of light under certain conditions.
The importance of colour is taken for granted, but it has a wide range of roles in our daily lives:

• It influences our preference in foods and other consumables
• It can reveal product quality and integrity
• It can indicate a persons health

Since colour has a ubiquitous influence on purchasing, colour measurement and colour control have become essential to manufacturers at all levels and across all applications.

What is colour measurement?

Based on the above diagram, we can see that Light strikes the Object (Car) and then gets reflected to the Observer (Eye). This information is then processed internally and we understand the colour to be “BLUE”. Measuring colour is replicating this action with known objective conditions. Under different lighting conditions or if we were to change the angle of observation, the “BLUE” colour would change in appearance.

This shows that the “BLUE” car is only blue under certain conditions, the colour of the car is a perception and not a property.

Components of Colour Measurement:

We require 3 compenents in order for us to be able to detect and measure colour:

1. Object
2. Observer
3. Light Source

Without all 3 of these components we cannot measure colour. In the same way that our eyes see, analytical instruments perform the same tasks to measure colour, with one major difference, Colour Measurement Instruments are objective and consistent.

Types of Measurement:

We perceive colour regardless of the nature of the object. An object that is completely opaque can be measured using similar principles to an object that is completely transparent. Depending on the object, we would either measure colour in Reflectance or Transmittance.

• Reflectance Measurements:

Reflectance measurements are performed for objects where the light does not completely pass through the object. These are typically opaque objects that can be in solid, powder, paste or granule form.

The light strikes the object, the light is then reflected off the object and the data is received by the detector. This is seen in our example with the “BLUE” car above or using the diagram below.

• Transmittance Measurements:

Transmittance measurements are performed for objects where some or all of the light passes through the object. These are typically transparent or transluscent objects such as films, sheeting or liquids.

The light is shone through the object and the data is received on the other side of the object by the detector. This can be seen in the diagram below.

If you are uncertain whether you should be performing a Reflectance or Transmittance measurement, follow these guidelines to test which measurement type is the best suited for your objects:

To test if the object is opaque, perform the following:

• Take a measurement under fixed conditions and record your reading.
• Take a second measurement, this time place your white standard behind your sample as you take the measurement.
• Compare the two readings. If the values differ, then the sample is not opaque as the transmitted light is reflected back.
• TIP: You could always use a white standard backing for a constant error.

Always remember that colour is a perception and NOT a property of the object. Conditions and instruments settings will alter the colour data you receive as you are changing the way your instrument may perceives the object.

For detailed explanations on colour measurement and colour physics, request an online or onsite visit with on of our experienced colour professisonals. This can be done conveniently by visiting The Narich Academy and completing a contact form.

Alternatively, if you want to get a comprehensive guide on colour and how to measure it, click HERE to download the Precise Colour Communication Booklet courtesy of Konica Minolta Sensing B.V.