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Creating a Digital Darkroom for A Color-Managed Workflow

 By Marc Aguilera

Creating a digital darkroom is one of the final tasks in implementing a precision color-managed workflow. It’s one of the often overlooked aspects of most digital photographic setups, however when taken seriously, a properly controlled “darkroom” and use of ICC profiles for your devices will yield the closest possible screen-to- print match.

First let’s talk about viewing conditions in the digital darkroom. Note that if you really want to go deep into this subject then I recommend you purchase the ISO Standard 3664:2000 entitled Viewing Conditions – Graphic Technology and Photography. If you would simply prefer the ‘just-tell-me-what-I-need-to-know’ version, then continue reading.

ISO 3664 basically states the obvious: (1) Light affects color; and (2) Your individual experience of color ultimately is subjective. It also states that while color measurement plays an important role in color control, color measurement will never replace the human observer for final assessment of quality. Furthermore, without question the best viewing condition is one which the final print will be seen, Nevertheless, ISO 3664 aims to provide a standardized specification for illumination and viewing conditions that when properly implemented ”...will reduce errors and misunderstandings caused by such deficiencies and inconsistencies.”

In other words, adhering to certain standards for viewing conditions within a digital darkroom makes it possible to achieve the best possible environment for making critical comparisons between transparencies, reflective photographic or photochemical prints, as well as overall appraisal of images on color displays which are not viewed in comparison to a hard copy.

Viewing apparatus.
When creating your digital darkroom, pick a light source that has the spectral power distribution of D50 - Daylight – 5000 Kelvin. You can get these types of lights from a variety of sources, including Solux, Just Normlicht, GTI, and X-Rite. The light source is crucial if you want images on your display and prints to come close to matching. The most economical way to go is to go with a Solux Task Lamp, although I prefer a well designed light booth. If you decide to build your own light booth be sure to minimize specular reflectivity and be sure the color of the booth is neutral. The color rendering index of the light source shall be 90 or higher and the illumination shall be 2000 lux +/- 500. The most important things to remember are that: (1) Light can greatly affect how your experience color; and (2) The best light source for viewing is D50 with minimal reflectivity, neutral colors for the apparatus, and 2000 lux of light.

Shown here is the digital darkroom of Harvest Productions in Yorba Linda, CA, an encompus color services account for which I provide training and consultation in the integration of ISO 3664:2000. It is a non-manipulated image of a typical workday. The original paintings and inkjet-printed reproductions are compared under a D50-balanced fluorescent light from GTI. However, the light source is reflected at an angle to reduce specular reflectivity. This was a custom design by Harvest.



This image is on location at the Color Control Freak Seminar sponsored by X-Rite and PANTONE. To demonstrate ISO 3664 principles, I brought along my Just Normlicht mini 5000 light. 




Surroundings
ISO 3664 states that the area immediately surrounding the displayed image shall be neutral, preferably dark gray. Also, the display should be situated so there are no strongly colored areas (including clothing) directly in the field of view because these may cause reflections in the display screen. Ideally all walls, floors, and furniture in the field of view should be grey and free of any posters, notices, pictures, wording or any other object which may affect the vision of the viewer.

As far as any interior paint is concerned ISO 3664 does not mention a particular paint or even Lab* value as long as it is neutral gray. My personal preference is the equivalent to Munsell N5 Gray, which in a PANTONE interior paint translates to 17-4402 TPX Neutral Gray and sells for $135 with Key Primer. If you’d rather go for a less expensive but equally good paint try Dunn Edwards Galax-z DE 1087 Dash of Ebony for around $45 per gallon.

I should also stress that the level of ambient light (the light in the environment surrounding your display) should be quite low. In fact, ISO 3664 states that ambient light should be under 64 lux and preferably under 32 lux of light. You can use an instrument such as X-Rite’s i1 Display and i1 Pro with free software called i1 Share to measure the amount of ambient light and its color temperature.The more ambient light there is in the room the more your display will have to compete with it, making the the likelihood of screen-to-print match that much more difficult. Do what is necessary to lock out the ambient light, even if this means shielding windows or turning off the surrounding lights.

Display Calibration and Profiling
It goes without saying that when creating a color-managed digital darkroom the display must be calibrated and profiled. The question really becomes what set of criteria do we calibrate to?

Essentially when you calibrate, you should choose a particular white point. ISO 3664 uses D65 as a white point and luminance must be over 75 cd/m2 (candela’s per meter squared) and should be over 100 cd/m2. I prefer 110-130 cd/m2. Also gamma should be set to 2.2. You may prefer a white point of D50 and gamma 1.8 if you send most of your work to publication but this is a choice you must make.

I learned years ago from one of my teachers in color that your viewing white point must match your display white point in order for the colors to really match. This advice has been important. Sometimes a display white point needs a bit of tweaking in order to get the best screen-to-print match. At encompus, we all have our displays calibrated to D65, 120 cd/m2, gamma 2.2. I get a decent screen to print match with my Just Normlicht mini 5000 light box.

Final Considerations
The major advantage of creating a digital darkroom is that you will gain efficiency in precision editing, especially when viewing color on screen compared to color on your print. Your viewing environment greatly affects how the eyes perceives color. A neutral environment with the correct lighting and positioning combined with a calibrated and profiled display and ICC workflow are the key elements in creating a color-managed digital darkroom.
Posted 12-09-2008 4:22 AM by Eileen Fritsch
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Comments

Gordon Webb wrote re: Creating a Digital Darkroom for A Color-Managed Workflow
on 12-11-2008 6:04 PM

How do I set white point and gamma... this isn't described.

Bill Barley wrote re: Creating a Digital Darkroom for A Color-Managed Workflow
on 06-10-2009 8:56 PM

How do I measure 120 cd/m2 using a conventional Gosson Luna Prof F light meter?

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