Color Management - or "How to make sure the grass looks just as green on both sides of the fence"

Color management is something you ought to be familiar with. Cameras, monitors, printers  and everything in between all process digital color in some way. Color management aims to relate device-dependent colors to standards in a predictable and consistent way, with the goal that photos always look the same as they transfer between devices, platforms and users.

Both Apple and Windows operating systems have a color management system (CMS) built in. A CMS maps color between devices such as monitors, scanners and printers, transforms color from one color space to another (for example, RGB to CMYK); and provides accurate on-screen or print previews.

Best practices and industry standards are applied on my side, but all these efforts are in vain and picture quality can suffer considerably, if image files are not handled correctly on the receiving end. You can even ruin images for good if you handle them wrongly.

To avoid any mishaps, some basics should be understood and observed. The following is meant to give you an introductory overview and equip you with some key knowledge about color management.

Color temperature, color space, color management, RGB mode, calibration, profiling, mismatch, rendering intent, gamut - what's it all about?

Well, just to put you at ease from the get go: I won't cover all of the above here in detail - that might be overwhelming. Some things I will even simplify slightly to enhance understanding.
Let's start slowly and look at the basic framework.

Modes and Color spaces

Digital Cameras and monitors work in values of Red, Green and Blue (RGB mode - additive). When such devices record or display photographs, each pixel ("picture element") has a value for each of these primary color assigned and combined this results in one of 16,7 million colors (in an 8-bit system).

Printers in contrast need to work in another color mode: Cyan, Magenta, Yellow, Black (CMYK - subtractive) - the colors of the inks that get printed. Images in the RGB mode need to be converted into CMYK mode for printing - but this involves an irreversible loss of color.

Therefore, photographs are generally delivered and archived in the RGB color space, since it holds more color information. It is best to keep images in RGB as far as possible in the workflow. This preserves color and makes it easiest to re-purpose image files for different types of print output, display or web use.

Various RGB color spaces are in use, with different characteristics. They particularly diverge in gamut (the ability to display a range of colors). The main ones are:

• sRGB - Represents "the lowest common denominator" and is suited for the web and used by many consumer cameras and monitors. It is a widely used color space - but being smaller in gamut, it clips (cuts off) some colors that can be printed and therefore is not well suited for professional imaging.
• AdobeRGB (1998) - Is a wider-gamut color space, well suited for printing and in common use
• ECI RGB - Also is an excellent, broad color space, used widely in the European printing industry

Color profiles

Color profiles link color characteristics of a device to the color management system; they are used for color matching and color conversion.

Some color profiles are device-dependent, e.g. for a camera, scanner or monitor. Associating the correct color profile with all of your devices helps to ensure consistent application of color throughout the publishing process.

Other profiles are device-independent: these are used by graphics software programs to define a "working" color space for editing images.
Profiles should be embedded into images to help the color management system match colors in the image to colors on an output device such as a monitor or printer.

Be on the same page

I choose to work in a large-gamut color space and therefore generally deliver images in AdobeRGB, it being most universally used.
This is also recommended for any image editing possibly done on your end, because you can always "down-convert" from a wider gamut to a narrow space such as sRGB. Conversely though, "up-converting" from a narrower to a wider-gamut space will not bring back the same fidelity and detail in color - it's gone for good.

Calibration and Color Profiles

To evaluate color accurately and reproduce it faithfully and consistently, the devices used should be color calibrated and color profiled.

Calibration is the process of matching a device as close as possible to a well defined, standard state.
Most consumer monitors and notebook displays are quite limited in quality and the gamut (range) of colors they can display. But, while the best results can only be achieved with high-end monitors, a good first step would be to adjust the brightness and contrast values, using a test chart (see links at end of article). A gamma value of 2,2 with a whitepoint of 6500K is a good target when working with images. To tune color, some basic software is available (e.g. Adobe Gamma) - but while this is certainly better than nothing, it leaves much to be desired.

To truly get dependable results though, one needs to use a Colorimeter, a device that measures the luminosity of RGB light, and matching software that takes care of both calibration and profiling.

ICC color profiles provide the translation between what an actual physical device can actually do, and the standards.
In photographs, an embedded profile does not change the image, rather it is the description of the color in the image. It communicates to a CMS (Color Management System), so your monitor and other color devices can use the color in the image correctly.

In a correctly configured color managed workflow, with the proper equipment, an image coming from my desk should look nearly identical on your end and in print. (Why only "nearly identical"? Because color perception is subjective, i.e. everyone sees color somewhat differently, and influences, such as ambient lighting, print surfaces, rendering intent settings, monitor quality etc., come into play as well.)

Use current imaging tools

By now you might also see, why it is crucial to work with current imaging tools, as recommended and detailed in my write-up on Digital Asset Management & Metadata.
Such tools insure that color-related information contained in the exif data stays intact throughout any photo handling process and color profiles and instructions are retained! Having access to the color data embedded in the photograph helps the publisher/ graphic designer/ printer/ web-designer etc.. It takes out guess work and allows correct handling, resulting in consistent reproduction and optimal results.

A note on sharpening - Why I generally don’t presharpen images

It's simple - images differ greatly and I don't want to compromise or second-guess the intent of your final use of the image. A ‘generic’ level of sharpening limits your creativity and the quality of your output could be sacrificed; sharpening is subjective. Printing environments and intent can vary widely. Different processes, environments and output sizes require different amounts of sharpening and what looks good on screen could look terrible in print, or vice versa. Ideally, sharpening is applied only as a final step before output.

In summary - what should all this mean to you?

To best benefit from me adopting Best Practices and applying industry standards and for optimal reproduction of images, you ought to:

• Be aware of color management and that color profiles are contained in image files.
• Evaluate your workflow in handling images.
• Encourage everyone involved in the workflow to understand and use color management, correct file handling and output sharpening.
• Always embed color profiles to images when saving, and preserve them when opening, for correct viewing, editing and handling. They contain crucial information about the color space they are in.
• Be aware that it is impossible to interpret the color numbers in an image correctly and with certainty if the color space is not known.
• Make mode and profile conversions carefully and only when they are needed in the workflow, keeping the originals intact.
• Use suitable, current imaging tools which incorporate color management - and take the time once to set them up correctly.
• Realize that if your monitor and system is not properly calibrated and profiled, any color and tonal evaluation or changes of photos you attempt is guess work.

If you adhere to these recommendations, you are well on your road to WYSIWIS (What You See Is What I Saw).
The effort is worth it, the results rewarding - and the images and your company will shine!

Should you have questions or are unsure about the correct processing of images you have received from me, do not hesitate to contact me. I'd be glad to help you make it all look good!

Depending on your needs and budget, I also offer additional retouching, as well as image optimization with individual tonal corrections. Just let me know how I can help.

On the following last page are some links you might find helpful.

Selected recommended links and reading:

• Image Receivers Guidelines - prepared by a coalition of the cream of the crop in imaging. With extensive list of resources and hints for monitor calibration
  www.updig.org
• European Color Initiative - a group of experts. Profiles, download monitor test images, infos
  www.eci.org
• Monitor Grayscale Test Image
  www.drycreekphoto.com/Learn/Calibration/monitor_gradient.htm
• International Color Consortium - Huge selection of excellent links
  http://www.color.org/info_profiles2.xalter
• "Advanced colour management for digital photography" - Presentation by Jack Holm/ HP, with sample images showing possibilities for drastic improvements by retaining exif data and color profiles in images
  http://www.color.org/documents/AdvColMgmt_for_DP.pdf
• Tests, if your browser is configured and able to accurately process color profile information
  
  • http://www.northlight-images.co.uk/article_pages/web-browser-color-management.html
  • http://www.color.org/version4html.xalter
• Practical Colour Management book which offers simple, practical advice on color management for photography etc.
  http://www.nativedigital.co.uk/shop/product.php/790/practical-colour-management---digital-download
• Digital-Image Color Spaces - a down-to-earth discussion/ explanation with many good links
  http://regex.info/blog/photo-tech/color-spaces-page7
• An Adobe glossary on Color Management terminology
  http://kb2.adobe.com/cps/320/320624.html
• Digipix3 Compendium for digital photography (as pdf)
  http://www.eci.org/lib/exe/fetch.php?id=en%3Adownloads&cache=cache&media=downloads:digital_photography:digipix3_v300_en.pdf

• Links in German:
  • Digipix3 Leitfaden Digitale Fotografie
    http://www.adf.de/apps/mediawiki/index.php?title=Digipix:Portal
    http://www.adf.de/wiki/index.php/Leitfaden_Digitale_Fotografie:Portal
  • Digipix3 (als pdf)
    http://www.eci.org/lib/exe/fetch.php?id=en%3Adownloads&cache=cache&media=downloads:digital_photography:digipix3_v301.pdf