The Darkroom Makes a Comeback (Part 2)

CreativePro Staff

8

Use D50 or Commercial 5,000°K Lighting
The most involved segment of your workspace overhaul may be shifting to 5,000°K D50 or commercial lighting, and upgrading your lighting can also be quite expensive. You don’t have to spend a lot to make big improvements over the everyday lighting most people use, however, and your options are numerous regardless of your budget.

D50 is just one of four hypothetical Standard Illuminants that represent various phases of natural daylight as defined by a group that sets international color standards — the CIE (Commission Internationale de L’Eclairage, or International Commission on Illumination). D50 is used for proofing purposes in the United States largely because it appears color neutral to the human eye and because it is close to the 4,100°K-fluorescent and warm 2,800°K-tungsten light sources typically found in offices and homes.

Depending on your needs and budget, you can spend between $35 and $1,200 for generic commercial or D50-compliant lighting products. Ultimately, you’ll want to decide between three types of 5000°K light sources:

• D50-compliant (daylight-balanced) halogen systems
• D50-compliant fluorescent lamps and luminaires (fixtures)
• Standard 5,000°K fluorescent lamps and commercial luminaires

D50 lighting systems will help you meet the ISO 3664:2000 and 12646 (draft) standards. Standard commercial 5,000°K sources merely are less-expensive daylight-balanced alternatives that allow for good but perhaps not perfectly accurate color viewing. Either of these choices should prove far better than common tungsten lamps and bulbs.

Fluorescent lamps are popular due to their energy efficiency, low cost, and widespread availability. Halogen lamps deliver a shorter average lamp life, generate more heat, consume more energy, and thus may be more expensive to operate. However, special daylight-balanced halogen lamps simulate natural sunlight more closely than any other manmade light source (including 5,000°K fluorescent), which actually skew some colors.

Because light is a form of radiant energy, it can be measured and charted using a spectral power distribution curve (SPD). The definition of SPD, along with the SPD curves of the D50 illuminant and some actual D50 light sources, are illustrated in Figure 3..

Lighting professionals analyze SPD curves like these to determine which man-made light sources most closely resemble the D50 standard. It is spectral power distribution, not color rendering index (so often printed on lighting packages), that is the most reliable indicator of the color accuracy of a light source. Unfortunately, SPD curves are not routinely communicated to consumers.

Lighting Suppliers: D50 Fluorescent
Purchasing D50 lamps and fixtures can be as simple as logging on to a graphic arts supplier’s Web site such as such as or Graphics Technology Inc. or Gretag-MacBeth LLC and ordering from online catalogs. Each company designs and manufactures color viewing and lighting products that meet the strict tolerance requirements of the graphic arts, photographic, and desktop publishing industries. Products include overhead luminaires for ceiling and recessed assemblies for countertop light tables, portable light boxes, desktop viewing booths, and custom 5,000°K fluorescent tubes in various lengths, all of which are manufactured to ISO specifications.

GTI will help design a lighting system if you articulate your needs and provide a measured drawing of the workspace. The company’s Soft-View desktop viewing booths, designed to sit next to a computer monitor, are very popular with photographers and pre-press professionals. Some models include a beam control system to adjust brightness levels that match your monitor’s output. A newer product line, the Professional Desktop Viewer, is a well-conceived viewing booth with a smaller footprint that is available in at least three sizes and eleven configurations.

In addition to overhead fluorescent fixtures, light boxes, and desktop-viewing booths, Gretag-MacBeth offers the Sol-Source line of filtered halogen task lamps The Sol-Source desk lamp provides daylight simulation using a patented, glass-filtered, tungsten-halogen light source (see Lighting Suppliers: The Halogen Option below). Gretag’s Prooflite Transparency Viewers are compact light boxes that can be placed on counters or hung on walls.

Lighting Suppliers: Standard, Commercial Fluorescent
At least one national building supplies chain — Atlanta-based Home Depot — sells Philips D50 fluorescent lamps and standard fixtures at comparatively low prices. The Philips Colortone 48-inch 5,000°K fluorescent tube (F40T12/C50) meets the ISO specifications for D50. Unfortunately, as of this publication’s deadline, Home Depot inexplicably stocked a different brand of D50/5,000°K lamp in the 24-inch (F20T12) and 18-inch (F15T8) sizes that are useful in smaller ceiling and under-cabinet luminaires — the General Electric Sunshine lamps. According to General Electric, the Sunshine lamps (F20T12/C50/24 inch and F15T8/C50/18 inch) offered by Home Depot do not meet the D50 illuminant specifications.

Though a convenient source, Home Depot’s use of two different brands of 5,000°K fluorescent lamps makes it difficult to standardize lighting when different lamp sizes are needed. You also should consider that individual commercial lamps from a mass-market assembly line might vary from nominal specifications unless every lamp is inspected or tested. This level of control is costly to implement, and it is one reason why the D50 lamps offered by companies such as Gretag-MacBeth are more expensive than ordinary 5,000°K lamps.

To some extent, replacing mass-market lamps long before usage reaches the 10,000- or 20,000-hour limits noted on packages can minimize this problem. In other words, for a low-cost solution that approximates D50 lighting, go with standard 5,000°K fluorescent lamps but change them out often — say, every few thousand hours.

Lighting Suppliers: D50 Halogen
The original Solux Daylight Lamp is a halogen lamp that has been called “the perfect light source for digital imaging.” In contrast to the 3,200°K color temperature of most other halogen lamps, one of the SoLux models (see Figure 5) has a 4,700°K white point and smooth spectral power distribution that closely simulates the D50 standard. Distributed (and sold directly) by Tailored Lighting, Inc. and USA Light & Electric, the product line is available via phone or Internet orders. Both Tailored Lighting and USA Light & Electric employ designers to help you create lighting plans.

The SoLux is a 50-watt MR-16 type lamp with a high color-rendering index (CRI) of 98 to 99 (out of 100). A 35-watt model is under development. It has been engineered to emit reduced infrared heat (IR) and ultraviolet (UV) light, but the actual color temperature can vary between 4,500° and 4,900°K, especially if the lamp fixture doesn’t operate at a full 12 volts (SoLux fixtures are designed to deliver 12 volts — and maintain color stability). The average life of a SoLux lamp is about 3,000 hours, but power fluctuations can affect performance. The lamp also is available in 3,500°K and 4,100°K models. Each MR-16 lamp retails for about $13. The lamps are available in 36° narrow flood, 10° narrow spot, and 17° spot models.

SoLux Track Lights are 12-volt fixtures in a stylized housing. SoLux Recessed Fixtures can include a reflector cone, wall wash, black baffle, eyeball with baffle, or gimble ring with baffle. A desktop Task Lamp, Clip-On Fixture, and a stand-alone fixture (Solar Simulator) also are available. Task lamps and two-light track systems sell for about $150.

Gretag-MacBeth, noted previously, offers a filtered-halogen task lamp, the Sol-Source, which sells for about $445 (with a weighted base).

Lighting Suppliers: Inexpensive Commercial Fluorescents
If you’re on a tighter budget, you may want to check with your favorite office-supply superstore. Stores such as Staples, Office Depot, and OfficeMax carry a selection of low-cost, fluorescent task lights for desktops at prices under $30.

Manufactured by a variety of companies, these plastic lamps usually have a small footprint, a flexible neck, and a weighted base. Most are equipped with a tiny, cool white twin-tube (4,150°K) fluorescent lamp (F13TT) that is unsuitable for digital imaging environments, but this lamp can be replaced with an Osram 5,000°K lamp (Dulux S F13TT50K) from specialty lighting stores for about $5. The 13-watt lamps (equivalent to a 60-watt tungsten bulb) provide just enough light to inspect a color print or proof. Unfortunately, these 5,000°K tubes do not meet the ISO/ANSI D50 specification, according to Osram Sylvania. Rated at 10,000 hours, the tubes should be replaced at about 2,500 hours to maintain color accuracy.

Finally, there is the venerable Ott-Lite, a fluorescent lamp originally marketed as a healthy, natural light system to reduce glare and eyestrain while improving your mood on dreary winter days. Environmental Lighting Concepts, Inc. of Tampa, Florida, is the parent company of Ott-Lite Technology. Ott-Lite’s $70 TrueColor Task Lamp is used by some as a low-cost color matching light source, but the firm’s newer VisionSaver Task Lamps are marketed to computer professionals as $80 (13W) or $130 (18W) models. Desktop, clamp-on, and floor model task lights all use the firm’s custom twin-tube (see Figure 5), 13-watt or 18-watt lamps with proprietary connectors.

Ott-Lite uses either six or seven rare earth phosphors in its lamps, depending on the product. Its design emits more mesopic (middle) lumens in the 470mm-to-500nm-wavelength range than most other lamps to increase visual acuity and improve color rendering. Since the Ott-Lite is rated at about 5,500°K, it technically does not meet the CIE/ISO color temperature specification for a D50 illuminant (5,000°K). And unlike other fluorescent manufacturers, Ott-Lite does not make high-resolution spectral power distribution data available so that its lamps can be easily compared with competing products. However, the lamps do produce a noticeably bright, relatively white (but perhaps slightly blue) light that is far better for proofing than tungsten or warm halogen lamps. Ott-Lite products are available direct from the manufacturer or through some retailers, such as Office Depot.

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