The ICC profile format has served us well since 1995, enabling documents to be translated between different media while achieving consistent colour. While a few die-hards extol the relative virtues of the original v2 profile format, version four has been increasingly ubiquitous since 2001, and is now seen being used to define standard colour spaces and to connect cameras, scanners, displays and printers everywhere. Importantly from a standards point of view, every international standard that references the ICC profile (of which there are 39 ISO and IEC standards, plus another eight de-facto standards such as JDF, PNG and CSS) points to the v4 specification, generally to the 4.3 version which was published by ISO as ISO 15076-1:22010. ICC recently released a minor revision, ICC.1:2022 (also known as v4.4) which clarifies some ambiguities and adds support for HDR image processing. This newer version is being proposed as an update to ISO 15076-1.
Yet in the 27 years since the ICC profile first saw the light of day, the whole technology of communicating colour has changed, and would today perhaps be unrecognisable to an industry professional of 1995. The old CRT displays went some time ago, and the CRT-based sRGB colour space is on their heels. Images are supplied in digital format, and the high-end scanner used to digitise photographs and transparencies has long been redundant. Commercial printers now in the main ‘print to the numbers’, and have hugely reduced their wastage rates by doing so. Volumes have fallen markedly in most the commercial print sector, as many types of product have been replaced by a web-based alternative. The packaging sector has seen expansion, and an increase in job complexity with for example extensive use of special colours, metallics, embossing and so on. We have also seen major clients specify house colours, not in the form of Pantones, but in terms of their spectral reflectance, colour measurement and possibly other properties.
Although ICC v4 still handles most requirements, there is an increasing number of cases where the job requirements extend beyond the basic processing model of v4, which is to convert device channels to a single profile connection space (PCS) based on D50 colorimetry in order to exchange data. The ICC v4 specification allows up to 15 colorant channels, which for practical purposes are limited to about 7 due to the necessary memory allocation, yet we are seeing jobs which have many more colorants being used. In v4 we also have no way to connect spectral data, without first converting it to D50 colorimetry. And as the use of ICC extends beyond the traditional graphic arts into the web, medical imaging, cultural heritage and other display-based workflows, there is a demand to be able to connect using non-D50 colorimetry.
To meet these emerging demands, and to ensure that the needs of colour management can be met for a long time into the future, ICC established the ICC.2 specification (also known as iccMAX). ICC.2 represents a huge leap forward, and introduces many advanced technologies into colour management. It allows connection not just through colorimetry, but also through spectra and through arbitrary channels; it permits any colorimetry to be used for connection (with D50 still as a default in case the sender and receiver are not using the same custom colorimetry). It also incorporates a powerful Postscript-like scripting language so that the profile creator can craft a precise transform that exactly meets the requirements.
So far only a limited number of products support iccMAX. It is a rich and complex specification, and if you can achieve what you want to do with v4, ICC’s recommendation is that you should continue to do so. Rather than support every iccMAX feature, developers are able to create profiles to an Interoperability Conformance Specification, which defines a subset of iccMAX that may be needed in a particular industry.
iccMAX was published as ISO 20677:2019. The technology continues to be fast-moving and ICC are preparing an update to the ICC version, which will make it into the ISO process in due course. In the meantime an extensive set of ICS documents are available on the ICC web site.
Phil Green, ICC Technical Secretary