There has never been more pressure on offset productivity and efficiency than now. Print runs are continuing to get shorter – customers demanding faster job turnaround times – which translates to more make readies and reduced profit margins. There is no question that if you have made an investment in auto scanning hardware system you are already ahead of the game. But are you getting the most out of it?

There are a number of parts or components to a closed loop colour control system and it is the sum of all these elements that really decides how much money you save by reducing your make ready costs.

To start let’s look into the elements that make up a viable closed loop control system:

Ink Pre-Set software – This is the software that usually takes a ‘CIP’ file that has been created by your CtP RIP. The CIP file contains the ink coverage information for each separation (CMYK + spots) and the ink preset software converts the data to ink key and sweep settings for each unit on the press.

Auto Scanning Spectrophotometer – This is the physical hardware component – the actual scanning instrument that scans and measures the colour bar (CB) patches from the printed sheet. Usually configured on the press console – aligned with the CB and automatically scans measuring each patch for each ink zone or key.

• Ink Pre-Set software – This is the software that usually takes a ‘CIP’ file that has been created by your CtP RIP. The CIP file contains the ink coverage information for each separation (CMYK + spots) and the ink preset software converts the data to ink key and sweep settings for each unit on the press.
  
• Auto Scanning Spectrophotometer – This is the physical hardware component – the actual scanning instrument that scans and measures the colour bar (CB) patches from the printed sheet. Usually configured on the press console – aligned with the CB and automatically scans measuring each patch for each ink zone or key.
  
• Computer Control and Interface to the Press – A computer platform is required (usually Windows PC), with a combination of sophisticated software and hardware to connect with the press console.
  Press manufacturers use different ways and protocols to interface or communicate with the press console – it could be a DPI (direct press interface) or a disk drive or via LAN (local area network) or even special hardware that emulates a memory type card. There is usually a way to communicate and interface with every press console available.
  
• Press manufacturers use different ways and protocols to interface or communicate with the press console – it could be a DPI (direct press interface) or a disk drive or via LAN (local area network) or even special hardware that emulates a memory type card. There is usually a way to communicate and interface with every press console available.
  
  
  

How does it all work? First the operator chooses the designated job with the ink pre-set data and sends that data to the press console. The software also manages the measurement instrument and displays the scanned data in an easy to follow and understand format. Ink key correction data can then be sent to the press. This is closed loop colour control in a ‘sense’ as you are adjusting the printed result based on the scanned measurements, making automated ink key adjustments and then the process is repeated to correct and maintain the desired evenness and colour. And yes, we are saying closed loop in a ‘sense’ as there is more that can be done to completely close the loop!

The initial ink key setting may not be in tune with how you are running the press for production. Fine tuning of the incoming ink pre-set data is required over time so the press can achieve the desired printed colour faster with each start up and make ready. Depending on your kind of work this can be completed relatively quickly – sometimes within days and weeks when new closed loop goes in. How is it done? When each production job is finished the ink key settings are recorded and then over time this can be compared to the initial ink key pre-set data. The ink ‘profile’ can be fine-tuned and adjusted for each process and spot so that the initial ink pre-set is closer and closer to the optimum settings for how the press is run for continued and successful production. This translates to much faster make ready for each job. Closing this final and strategic loop can get you to 95% or better on being at the correct production quality level.

Now consider the savings over time – with a completely closed loop system you can reduce make ready from thousands and many hundreds of sheets down to a 100-200 sheets. Doesn’t sound like a lot – over time it can add up to a lot of savings when applied to every job on the press.

There additional benefits of closed loop as well. Targets and standards can be maintained easily from within the system – reprints can be achieved, with less hassle to the previous colour as the job is saved with all the ink settings. The press operator will have more time to ensure the print quality is up to scratch – registration spot on – hickeys and other defects that can occur from time to time will be picked up.

The return on investment can be faster than you think, often within 6 months. Colour is a very important part of overall print quality, but if you can get it right, every time, you will move to be being a more successful profitable company – saving money on each job is the power of complete closed loop control.

To find out more about print quality management and printer colour management colour management please contact us via our contact form

There is no such thing as a standard CYAN. You cannot go down to your local standards office, open the big safe and find a tin of standard Cyan inside.

Valuable production time can be lost due to the colour of ink the just not being right or not suited to job at hand. Other things can combine with this, such as, substrate type and using the correct colour measurement instrument and settings.

Let’s have a look at the key points to check in the press room.

1. Check the Ink
   For process inks, especially if you are printing offset sheet fed or heat set web to ISO 12647-2 your inks should meet ISO 2846-1, as a start. This is a normative reference in 12647-2.
   For special colour inks a draw down sample from your ink supplier is a good place to start. Even better if this is done on the substrate you will print with.
   The draw down can then be measured and the spectral data incorporated into your colour analysis and reporting software (e.g. Mellow Colour PrintSpec or InkSpec) as an in-house standard. If the draw down is supposed to match a ‘library’ colour you can use the in-house measurement data for reporting through your internal quality dept and for improving the match through further discussion with the ink supplier.
   Either of the above is really required otherwise you will be flying blind, so to speak.
   
   
2. Check you are using the right instrument
   You should be using a spectrophotometer with 0/45 or 45/0 illumination. This is the standard geometry instrument that suits most printing and packaging applications. Some highly glossy flexible materials, metallic inks and gold or silver foils may require a spherical spectrophotometer. These types of materials will not measure the same way that we see that colour when using a 0/45 or 45/0 instrument. A spherical spectrophotometer can be set up exclude or include the gloss component – excluding the gloss can provide an improved visual colour match depending on the material being measured.
   
   
   
   ‘SEE the sample diagram above’
   
   
3. Check your instrument measurement settings
   Make sure you are using the same, and correct, settings for the illumination and observer according to the standard. Most colour standards will specify D50/2 degrees – some brands and paper manufacturers may use D65/10 degrees. Check you are using the same illuminant and observer as specified.
   
   
4. Check your measurement mode
   This is like choosing a filter setting in your spectrophotometer. The latest ISO 12647-2:2013 specifies M1 mode, to adjust and allow for the increased use of optical brighteners in substrates today. You may have been or are currently using M0 mode which is the older ‘legacy’ setting for most older instruments. Check what is specified in the standard. Changing to M1 can mean a lot of re-measuring standards etc., but it is worth it in the long run. Other modes are M2 (UV cut) and M3 (Pol filter).
   
   
5. Check your Backing
   When you measure a thin or slightly transparent substrate you should always use the correctly specified backing material, underneath the substrate to be measured. Black backing ensures there will be no influence of what is underneath the sample or printed on the other side. White backing is the standard for measuring digital proofs. If you print flexo, and / or just print on one side, white backing will be fine. And there are ISO standards for backing.
   – It is worth noting that the next revision of ISO 12647-2, due in 2027, will only include data and co-ordinates for white backing.
   
   
6. Check your dE (delta E) setting
   What dE tolerance method should you be using? What is specified in the standard? ISO 12647-2 uses CIELAB dE or dE 76. Many print buyers and brands are specifying dE 2000. Make sure you are using the correct dE according to your job and standard.
   
   
7. Check your measurement and reporting procedures
   Measurement of printed samples and reporting should have a clearly defined step by step procedure. This will help avoid mis-reads of samples and strange report results appearing randomly. A procedure or set of procedures should be available to all who are responsible in the colour workflow. These are sometimes called standard operating procedures (SOP’s). A set of SOPs also enables new staff to be trained correctly and effectively.
   
   
8. Check the measurement data source
   Target L*a*b* values should be created from spectral measurement data. L*a*b* values require reference information, such as;
   
   a) illuminant and observer (e.g. D50/2 degrees)
   b) Type and Specification of Backing (White or Black)
   c) Measurement Mode (M0, M1, M2 or M3)
   d) Instrument Geometry, Instrument manufacturer, model, etc.
   e) Instrument certification (up to date?)
   f) Instrument aperture size (2mm, 3mm or ?)
   
   Straight L*a*b* values with no reference data will have no meaning and cannot be used to accurately communicate colour.
   
   

As you can see not all colour measurement is equal. Care and attention needs to be taken when measuring standards and samples!

For more information about the benefits of using a Colour Spectrophotometer training and the TECHKON 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