You have taken the utmost care with the latest ‘XYZ’ brand packaging print job.

Measured and verified the digital proof is within the required ISO 12647-7 tolerances for CMYK and for the brands spot colours.
Measured and checked that the viewing conditions on press and your viewing system in the quality department are within ISO 3664.
Measured, checked and reported that the required number of printed samples are within the customer requested tolerances (dE, TVI, Grey Balance).
Checked and completed in the in-house validation of the measurement instruments used.


Checked that the instruments used are up to date for manufacturers maintenance, service and certification.

All ok from your side, right! But your customer is complaining that the colour is no good, out of tolerance….

Why is this happening?

We often get called in to help and assist sort out situations like this. The solution is fairly straight forward. 


• You need a documented Colour Quality Measurement procedure that clearly defines how colour is going to be measured, analysed, reported and viewed.
• There needs to be agreement by all parties concerned.

• All parties then need to follow and adhere to the agreement.


What do you need to include into the colour assessment procedure?

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1. Instruments: You and your customer maybe be carrying out colour measurement but that does not mean you will get measurement agreement. What do need to consider about colour measurement instruments?


   
   Type?

There are various types of instruments – Densitometers, Colorimeters & Spectrophotometers.

   
   Densitometers are mainly used to measure the ink film thickness. i.e. ink on paper, more ink = higher density. Good for process control for hitting target densities when printing and checking if the inking is even across the sheet. A densitometer can also tell you about dot% and/or dot gain-TVI (tone value increase). A densitometer is a colour-blind instrument.

A Colorimeter is a low-cost way to measure and do basic evaluation. 

   
   A Colorimeter uses only 3 filters (RGB) to capture colour…


   
   Spectrophotometers are at the top of the pile! They provide the most accurate capture of colour.




   
   Geometry and Model?

There are basically three types of spectrophotometer geometry – 0/45 or 45/0, Sphere and Multi- Angle.


   
   All three of the aforementioned have their place, but they work entirely differently. Two spectrophotometers with the same geometry will not measure colour exactly the same due to manufacturer differences and instrument specifications.


   
   To confirm measurement consistency everyone should use the same type, and model of spectrophotometer.



   
   What Aperture Size?

All spectrophotometers have an aperture that is a fixed size. It could range from 1.5mm to more than 20mm. The size of the aperture definitely has an effect on the measurements. You need to use the right size aperture to suit your ‘job’ at hand. Measuring 3mm square printed patches? You will need to use a 1.5mm aperture for spot measurement.



   
   Using a larger aperture for spot measuring 3mm patches and you run the risk of including the background or surrounding colour outside the patches.


   
   Everyone should be using the same size aperture.





   
   Measurement Mode?


   
   Spectrophotometers can have different measurement modes and settings. In 45/0 instruments the measurement mode is usually set and controlled by the M condition. i.e. M0, M1, M2 and M3.



   
   It is vital that everyone uses the same mode!

   
   Measurement Backing?

For print measurement this is very important. Black or White Backing?
For double sided print material, on a thin substrate (e.g. 80gsm paper) you should use Black Backing to stop the show through or to stop the influence of printed colour on the other side of the substrate 2∘. Information about the standard for backing is contained in ISO 13655. You can also use some software tools to evaluate whether your backing is within the tolerances of the specification.


   
   Everyone should the same specification of Backing.


   
   Illuminant and Observer?


   
   The Observer angle will directly affect the measurement results. For ‘print’ colour measurement the Observer is usually set to 2∘. Spectral measurement data for print is usually converted to L*a*b* using D50/2∘ – (Illuminant and Observer).



   
   Make sure everyone uses the same Illuminant and Observer.


   
   In-House Validation, Calibration and Manufacturers service and re-certification?



   
   Like all things mechanical, your instrument requires scheduled checks and service. Having a procedure and for in-house validation and keeping records is a great way to track your instrument ‘behaviour’ or condition.


   
   Your spectrophotometer is a significant investment – look after it – keep it clean, well maintained. Keep your measurement check samples clean. Follow a good calibration procedure – Calibrate every time your start a ‘job’ and at least once a day. 


   
   No one likes to be without their favourite instrument! But sending your instrument back to the manufacturer ensures the instrument is measuring and performing within specification. Manufacturers service and re-certification provides peace of mind and also ensures you are up to date for compliance.


   
2. Viewing Conditions (Illuminant)


   
   The viewing conditions used to assess your colour print results should be standardised across departments, sites and customers.



   
   For print this means conforming to ISO 3664:2025, which means using D50 for colour assessment, evaluation and measurement (as mentioned in the previous point in this blog!).


   
   I see all too often a casual approach taken to critical visual colour assessment being completed under non-standard factory lighting or office lighting. THIS IS USUALLY THE EASIEST THING TO FIX AND CONTROL! More often than not, someone’s comments about ‘bad’ colour issue from looking at a printed result or digital proof under non-standard lighting conditions.




   
   ISO 3664:2025 viewing conditions, of the same type, should be strictly adhered to wherever the print samples are to be visually checked for ‘colour’.
3. Colour Definition and Tolerance


   
   There are many ways to define and describe colour, which has caused a huge amount of angst among colour specifiers, quality departments, manufacturers and suppliers.



   
   We would recommend using L*a*b* as the means to define a colour target or reference. You will also need to describe how the L*a*b* co-ordinates were achieved.


   
   – Illuminant and Observer?


   – Aperture size?

   – Measurement Mode?

   – Backing?

   – Instrument Geometry, Type and Model


   
   What is the tolerance amount and the tolerance methodology?


   
   Defining a pass/fail tolerance should be in line with industry standards (i.e. ISO 12647-2), as well the capability of the production process. And, best of all discuss this at length with your customers, as they are the ones whom you are endeavouring to please and look after!
You may use a tolerance of dE 2~3 for spot or custom printed colours…


   
   The tolerance methodology could be:

   – CIELab (1976) – dE

   – CIE94 – dE94

   – CIE2000 – dE2000
The latter is now commonly used for brand or spot colours…


   
   The colour definition, tolerance amount and tolerance methodology should ALL be clearly defined, documented and followed by you and your customer(s)!

   
   
4. Measurement Method


   
   We covered most of this in the previous point when we discussed about using L*a*b* and how those numbers arrived at.
Importantly the measurement method should be same across departments, sites and with your customer.


   This may include using ‘averaging’ when measuring samples and creating a colour definition or standard. 

   
   
5. Environmental considerations and the effects on the standard and sample(s)

   
   Factory and Office environments can vary widely depending on the manufacturing and production process. This can obviously have an effect on the measurement instrument performance and the condition of the sample(s) to be measured.


   
   Therefore, measurement should always be done within the same environmental conditions to ensure consistency.


   
   Printed samples can be affected by ink dry back, UV inks, aqueous coating and varnishes. 


   
   ISO 12647-2 (Offset print standard) states that the measurement is based on dry samples…


How do you eliminate customer disagreements with colour assessment and measurement?

1. You need a documented Colour Quality Measurement procedure that clearly defines how colour is going to be measured, analysed, reported and viewed. It has to be standardised!
Include specifications for:
   – Instruments 

   – Viewing Conditions

   – Colour Definition and Tolerance amount and methodology

   – Measurement Method

   – Environmental considerations

2. Identify the variables in the production process
3. There needs to be agreement by all parties concerned, and test the process
4. All parties then need to follow and adhere to the agreement.


   
   It is possible to improve and maintain predictability with colour. It takes some effort to set up colour assessment and a Colour Quality Management system, but the long-term benefits far outweigh the on-going arguments, disagreements, loss of production, job re-prints, etc…

   
   

For more information about Colour Spectrophotometer training and the TECHKON SpectroDens instrument range please contact us via our contact form

D
ensitometer and Spectrophotometer – What is the difference?

These are the two colour measurement instruments we get asked the most about. Each has their place, and purpose, so in order to decide which is appropriate it is essential that we delve into each devices characteristics, details and functionality.



1. Densitometers

Densitometers traditionally come up with a density ‘figure’ when measuring a solid patch of colour, usually Cyan or Magenta or Yellow or Black (print process colours). Printers will recognise densities like 1.45 for Cyan and Magenta, 1.05 for Yellow and 1.7 for Black, based on ISO or ANSI Status T.



A densitometer uses a filter that is complimentary to the colour being measured.

Cyan -> Red filter

Magenta -> Green filter
Yellow -> Blue filter



As such we can describe a densitometer as a colour-blind instrument. Simply put the filter makes the colour appear a shade of black and density is based on a logarithmic calculation. i.e. Density = Log₁₀ (remission).
Remission is a measurement of reflected light, which means 1.0 is perfectly reflective and 0.0 is perfectly absorbent. Using the equation above, a grey patch that has a remission of 0.50 (or 50% reflection), would yield a density of 0.30 D.



This makes a densitometer great for determining ink film thickness (density) and when used correctly will easily pick up large, and subtle, variations in density that the human eye cannot detect.

A densitometer easily becomes the printer’s friend as they can also provide additional measurement data for;

• Dot Area
• Ink Trapping
• Dot Gain
• Print Contrast
• Slur and Doubling

  

It is important to understand that a densitometer does NOT measure the actual half tone dots – it measures the density or tone value. Mathematics is then used for dot area and dot gain calculations.


Monitoring tone reproduction quality is especially important across all print processes, offset, flexo and digital. Just getting the solid densities in tolerance does not guarantee good quality colour reproduction.



Some densitometers are capable of measuring according to one status type.
Therefore, it is important to know what density status you are using and to always identify that when communicating or reporting density measurement values.

As a guide:

1. Status T, with no polarisation filter is commonly used in the USA
2. Status E, with polarisation filter is used throughout Europe
3. Status A, M and I may be used in other applications like photographic

2. Spectrophotometers

A spectrophotometer is a complex precision instrument and therefore will always cost more than a densitometer.



A Spectrophotometer typically captures a colour sample from across the visible spectrum (400 ~ 700 nanometres) and provides a spectral data curve or spectral ‘fingerprint’. With spectral data you are able to qualify paper and ink. Is the ink supplied within the required tolerance? i.e. A spectrophotometer can tell you if your CMYK ink set can print within ISO 12647-2 tolerances. Or if the spot colour is within dE (delta E) tolerance to match the required brand colour?



The spectral data is usually converted to metrics to describe the colour, such as LCh* (Lightness, Chroma and Hue) or Lab*. These metrics closely resemble how we perceive colour.

There are different types of spectrophotometers used in industrial applications, like automotive paints, architectural finishes and coatings, paint formulation and finishes, ink formulation and finishes, plastics and, in print areas, for paper and substrate manufacture, ink and colourant formulation, proofing calibration and verification, press room colour control and print QC/QA.

Spectrophotometers are also commonly used in colour management across image capture (think colour scanners and digital cameras), displays (colour monitors), inkjet, digital and wide format printers for CMYK or RGB output, in fact anywhere in print where colour measurement and colour reporting is required.

For more information about Colour Management training and the full TECHKON instrument range please contact us via our contact form