Proof4press is a set of best practice guidelines oulining issues to be aware of when choosing a proofing system.
The importance of proofing
Specifying an appropriate proofing system is crucial to managing expectations in the supply chain. Clear and concise guidelines coupled with the effective use of International Colour Consortium (ICC) profiles will help you maintain consistency and accuracy.
Proof4press recommendations
Proofs provide an early view of the predicted final printed result, so you can either confirm that your page will print as expected or at least be warned of potential problems. Proofs help manage expectations, so without consistency, accuracy and relevance to the final product, a proof is effectively worthless. When selecting a proofing system, or specifying specifications for the proofs you will accept, several things must be taken into consideration: the paper stock you use; the device you print on; the measurement equipment you use to verify the printed result and the lighting of the environment in which you view it; and then it must all bear a good relation to the printed product. In addition, a publication that utilises a glossy bright substrate for proofs but prints on an uncoated paper will always set expectation levels unrealistically high. The only way to tackle proofing successfully is to take a holistic approach.
Proofing devices
The first step is to choose the specific proofing output device. The manufacturer and model should be chosen according to your quality expectations, but we would recommend using a system that has gained accreditation through an international body. Both FOGRA in Germany and UGRA in Switzerland offer these services, and the majority of major proofing vendors put their models through one or other process. In the UK, the British Printing Industries Federations (BPIF) is considering the provision of a certification process.
Colour space/profile
This must be based on your publication’s paper type and printing conditions, and agreed only after liaison with repro and printing partners.
Tolerances
The tolerances of ISO standards relating to print are far too high for use in proofing – for example, the FOGRA Media Wedge spreadsheet dictates a maximum Delta E value of 10 on a single patch and an average of 4 across all measured patches. They are at that level because they represent what is achievable on a large press, rather than a desktop proofer. For proofing, FOGRA has introduced an additional set of criteria that checks against the reduced tolerance values specified for proofing by ISO. These tolerance values will still be too large for high quality work. Bringing these to more acceptable values for proofing will require proof providers and receivers to locally agree acceptable tolerances by discussion and negotiation, set in relation to the quality threshold required. Extensive testing will likely be required to find the optimal numbers for acceptable maximum and average Delta E values. Any locally agreed values should also fall within the appropriate ISO and FOGRA tolerances.
Printing conditions and paper types
Gravure printing is increasing in popularity. Because of its specific nature, there are no current standards to represent general conditions. So always liaise with your print suppliers to agree specification and profiles. Although not currently part of the ISO standards, an SC paper profile is also available from the European Colour Initiative (ECI) as part of their web offset profiles package.
Soft proofing
In areas where quality is less critical, soft proofing systems are being used as viable alternatives to hard copy proofing. There are many systems on the market, but they do face challenges in regard to monitoring and maintaining consistency across remote users, and particularly with inter-operability between different vendors’ systems. However, large companies such as Time Inc in the USA and News International in the UK are successfully using soft proofing for receipt of advertising. It is still relatively early days for this technology, but a lot of innovative work is being done to find solutions. In the UK, the Digital Ad Lab, in conjunction with the Ghent Workgroup, have an initiative that is monitoring the soft proofing industry and working to effect consistent, metadata-based links between systems.
Profiles
Maintaining accurate colour throughout your workflow relies on effective colour management, and therefore the correct use of profiles. When dealing with the commonly used paper types in the UK which conform to ISO paper types 1-3, Pass4press version 9 recommends using the FOGRA 39L and 28L characterisation data and the ECI-produced profiles (ISO Coated V2 300 ECI and ISO Web Coated respectively). Adobe Creative Suite 3 contains a profile called Coated FOGRA39L – this has been created from the same characterisation data as the ECI profile, but has a higher TAC of 330%. This may be too high for some jobs, so check with your supply chain before utilising it. The equivalent FOGRA media wedges should be used for verification purposes, with appropriate tolerances. This data was measured from printed sheets produced under controlled conditions, and experience has shown that the data is typical of press conditions.
By using real press data as aim-points for colour proofing, colour is easier to match on press than using proofs made to values established from pre-press proofing systems. This results in less compromise on the press when trying to achieve a colour match. A characterisation data set contains CMYK (or RGB) combination values of test target patches, together with their measured CIE colour (CIE Lab and XYZ) values.
For proofing, the most commonly used test targets are known as ECI2002, which originated in Europe, and IT8.7/4 (from ISO12642), which contains all the patches in ECI2002 plus extra patches that meet flexo requirements. This is the data that is used to produce ICC colour profiles using specialise software packages. It is important to note that according to the ISO release the new FOGRA 39L characterisation data is a direct replacement for FOGRA 27. All workflows utilising FOGRA 27 should be upgraded to FOGRA 39L. Which specific ICC profiles you use for a colour conversion depends on the job, but the destination output device must always be taken into consideration. See the Pic4press Version 3 Guidelines for more details on profiles and their usage.
For more information on production issues and Proof4press email rose.benjamin@ppa.co.uk.