An ICC profile by itself by itself does nothing, it is simply a colour description waiting to be used. You need at least two profiles to achieve an outcome. Profiles only work in a transform or conversion – you need a source and a destination profile. e.g. a source profile could be “sRGB” and the destination a CMYK print profile. This means the RGB file with the assigned sRGB profile will be converted to the CMYK space of the destination profile, under the control of the chosen rendering intent – Saturation, Perceptual or Colorimetric. Profiles communicate with each other in a common language, such as “L*a*b*” or “XYZ”.

An ICC profile gives meaning to the RGB or CMYK numbers in a file. For example, a scanner captures RGB information. The scanner RGB ICC profile provides meaning to how the scanner behaves and captures the RGB colour. The profile does not correct how the scanner captures colour it simply describes how the colour is captured. Now if you wanted to display the scanned image correctly you would need to make a monitor ICC profile. Profiles always work in twos!

We have oversimplified it a bit here, as colour management can be complex, but all you have you to do is follow some rules.

C stands for?

Before building a new ICC profile for a scanner, camera, monitor or printer you should calibrate the device first.

Calibrating is the most important step before creating an ICC profile. Calibration is about getting your device into a known, quantifiable and repeatable state.

What does this mean? On a monitor you adjust the brightness and RGB controls until you hit predetermined luminance and colour temperature targets. On an inkjet printer outputting through a RIP, calibration means setting up per channel ink limits, overprint ink limits, CMYK linearisation and grey balance control – it’s about ink media compatibility. Both aforementioned required measurement with an instrument (colorimeter or spectrophotometer) which makes it quantifiable. And if it is quantifiable, then it is repeatable.

After your calibration is complete you can then create your ICC profile.

If your device changes or wanders over time you can re-calibrate it back to the known settings and your existing profile will still be valid.
This is the benefit of having a good calibration process in place.

Every device is unique

Every device colour behavior is going to be different, which is why calibration is so important. Especially if you have multiple devices that you want to simulate to a common output colour space – think ISO Coated v2 (Fogra 39) or PSO Coated v3 (Fogra 51).

Every device colour behavior is going to be different, which is why calibration is so important. Especially if you have multiple devices that you want to simulate to a common output colour space – think ISO Coated v2 (Fogra 39) or PSO Coated v3 (Fogra 51).

Colour management is not perfect – there are device and colour limitations. And sometimes our expectations are set unrealistically too high. Colour measurement, human vision and viewing conditions all need to be properly defined, described and explained.

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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!

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We are going to look at choosing a spectrophotometer for use within printing – covering offset, flexo, digital and wide format print. In these areas the substrate can be paper, carton material (board), flexible packaging material (plastics, polypropylene, etc.) and in the wide format area flexible (i.e. self-adhesive, banner, etc.) or rigid material (screen board, core flute, foam core, etc.)

When deciding which spectrophotometer is right for you there are a number of things to consider.

1. What sort of substrates are going to be measured?
   
   For ink on paper, sheet-fed offset, heat-set web offset, digital production print and digital proofs, using fairly standard thickness stocks (up to around 400 gsm) a bench top automated chart reading (Bench top) spectrophotometer may seem to be the right choice here. But there is another couple of areas to consider as well, which we will cover in the next steps.
   
   If you need to measure rigid type materials, such as “core flute”, foam core, screen board, plastic sheeting”, amongst others, a handheld instrument might seem like your only choice. But there are Bench top spectrophotometers that can measure substrates up to 20mm thick, according to manufacturer’s specifications. These instruments also offer the ability to measure transparent media, such as ‘backlit’ material.
   
   What if you need to measure flexible packaging material, like a thin ‘polypro’ used in flexo printing. You may be able to use either type of spectrophotometer here, but you will need to consider the use of a standard ‘backing’ (white or black) because of the colour show through with this type of substrate.
2. How will you use your Spectrophotometer?
   
   Will you be measuring charts for ICC profile colour management? Will you additionally need to spot measure or scan ‘patches’ of colour for QC and QA? Do you need your spectrophotometer to work with third party colour management software? Do you require portability? – i.e. taking a handheld to different areas/depts on site or even to other sites?
   
   How you wish to use your spectrophotometer may well be the determining factor here…
3. Are the ‘instruments’ going be part of a ‘workgroup’?
   
   Will all the usage of your instruments be centralized? Or will there be a number of instruments from across various sites that require correlation with measurement accuracy?
   
   If say, you are going to use three spectrophotometers across three sites then you should consider using the same type, model and specification. Not only are you dealing with one instrument repeatability, but you are also have to think about the tolerances of each instrument.
4. Does the instrument conform to ISO 13655:2009 for measurement modes M0, M1, M2, M3?
   
   This is important for ‘print’ measurements as quite often the substrate contains an amount of optical brightening agents (OBA’s). Many spectrophotometers available now can use the measurement conditions M0, M1, M2, M3.
   
   Many older spectrophotometers only used M0 – an incandescent lamp with relative spectral power close to CIE standard illuminant A.
   
   M1 aids in minimizing measurement differences between instruments due to OBA’s and fluorescence, by matching CIE illuminant D50. ISO 3664:2009 specifies D50 as the standard viewing condition for print, graphic arts and photography.
   
   M2 is similar to the previous usage of a UV Cut filter – to exclude differences in measurement due to fluorescence of OBA’s in the substrate.
   
   M3 is essentially the same as M2, but includes a polarising filter to remove and or minimize reflections – also differences between wet and dry inks (dry back).
5. Do you require your spectrophotometer to measure according to standards?
   
   The ISO 12647-2:2013 standard states that measurements “should be made using M1”. Therefore if you are using 12647-2:2013, or a later amendment, you should be using M1 mode, with white or black backing.
   If you are going to use an in house standard or something specified by your customer or brand owner then this should be clearly communicated stating the illuminant, observer, geometry, backing and /or alternate mode. i.e. M2.
6. What is your budget?
   
   I leave this obvious point to last – not that the above points are in any particular order. Price is always going to be a consideration – but the quality of a spectrophotometer will be remembered long after price is forgotten. You need to be realistic here as these are precision instruments that require care and looking after. You should have your spectrophotometer(s) checked, serviced and re-certified by a reputable instrument laboratory or the manufacturer at an interval according to the manufacturer or set by your quality management system policy. Either way it is best practice to have an in-house validation procedure in place, together with records.
   
   So, which spectrophotometer to choose – handheld or bench top?
   Your choice can be narrowed down depending on how your answer the previous 6 points.

For more information on setting up and looking after Printer Colour Management, Printer Colour Calibration, on site Colour Consulting and Colour Management training contact us via our contact form