Why specify version 4 profiles?

ICC strongly recommends that writers of standards documents specify the v4 profile format, where possible referencing the most recent specification version ISO 15076-1:2010.

ISO 15076-1:2010 is a high quality specification which has been carefully edited to avoid ambiguity and enable the greatest possible interoperability. When referencing the ICC profile format in other standards and implementation workflows, ICC strongly recommends that such specification documents indicate that the user *should* use v4 profiles but *shall* use ICC profiles.

ICC recommends the v4 specification for the following reasons:

1. ISO 15076-1:2010 provides a clear and unambiguous reference for ICC color management, to resolve user and implementer conflicts and confusion, and encourages improved consistency in implementations

2. While v2 profiles made using the v4 features that are compatible with v2 may give equivalent results to v4 profiles for certain combinations of color encodings, conformance to the v2 specification does not ensure consistency and improved rendering across the full range of inputs and outputs in the same way that conformance to v4 does. Use of v4 thus provides a higher level of assurance of reproduction quality in workflows that involve data with a range of different sources and destinations.

3. Additional features in v4 offer a wider range of functionality which may be desirable in certain workflows, such as automation using profileID for profile identification and verification, support for non-Western fonts in test fields, the potential for better handling of spot colour and Device N, support for scene-referred source data, smaller profiles of equivalent quality and the removal of redundant tags.

4. Added transform flexibility through the use of lutAtoB and parametric curves makes it possible to create smaller, more accurate profiles

5. The chad tag required in v4 profiles enables CMMs to support varying levels of chromatic adaptation and to perform direct source to destination adaptation

6. Since it is not possible to convert v2 to v4 profiles without additional information and in some cases it is not possible to convert v4 profiles to v2 without loss of quality, there is the potential for issues such as loss of colour accuracy if workflows are limited to using only one version

7. The way in which CMMs should perform colour conversion when profiles of different versions are combined is not well defined, because the v2 specification is ambiguous. This means that unless both profiles are v4 there is a chance that the result will not be as the creator intended

V4 raison d'etre to enable intelligent CMMs and improve results for non-linear color spaces contains the V2 - V4 technical changes and benefits list.

While ICC recommends the use of v4 profiles wherever possible, it recognizes that v2 profiles continue to be used in some workflows and can give good results under limited conditions. Some recommendations on making v2 profiles are provided for developers.