We use these HPS (high pressure sodium) from e-conolight. I see they're on sale right now. The 400w is a pretty hefty unit, but it will light things up. They take 2-3 minutes to attain full light. They are available in either HPS (high pressure sodium = orangish color), or metal halide (= blue-whitish color)

http://www.e-conolight.com/wall-packs/standard/standard-320-400-watt-hid.html

Following is copy/paste about HPS vs MH light advantages. I hesitantly bolded the last line:

Metal Halide vs. High Pressure Sodium

Metal halide lighting differs from High Pressure Sodium (HPS) in the color and quality of light delivered. Metal halide is a highly efficient light source capable of delivering a white light in the range of 2700 to 5500 Kelvin with typical CRIs in the mid-60s to mid-70s. Some lamp chemistries even obtain CRIs in the 80s. In contrast, high pressure sodium lamps yield yellow lighting (2200K) and have a very poor color rendering index of 22.

HPS lamps are available in color-corrected versions that shorten their life and only slightly improve color temperature. Even with greatly improved CRIs, the color temperature still delivers yellow light. This color limitation is present because the HPS lamp generates light through the excitation of sodium. Metal halide lamps, on the other hand, generate light through the excitation of 2 to 5 different chemicals in the arc tube. In addition, the exclusive Uni-Form formed body arc tube is a newly-designed, compact light source sculpted to follow the physical shape of the arc itself. The precise geometry of this unique arc tube, accurately reproducible from lamp to lamp, produces a metal halide lamp of greater efficiency, improved color uniformity, and longer life.

By varying the blend of chemicals in the arc tube, metal halide engineers are able to alter the characteristics of the light output. This flexibility in design makes metal halide so versatile. White light is a very important attribute of metal halide technology, because it is the closest to the natural sunlight that people prefer.

A number of independent research projects compare each option under low light levels and provide solid, reliable information to support the concept that the color of light strongly influences human perception. In fact, the sensitivity of the eye to different colors determines the true or effective lumen output of a lamp. The visual effectiveness of white metal halide light with a high blue/green content is shown to increase in reduced light while it decreases for the yellow light of sodium sources.

High pressure sodium has been used for years in less color critical applications such as parking lot and roadway lighting. Applications more sensitive to color have used metal halide. The availability of lower wattage metal halide lamps and the revolutionary Uni-Form pulse start system technology has greatly increased its application in indoor and outside commercial and industrial environments. Many applications, such as security and parking garage lighting, now use metal halide instead of HPS. HPS is used today mainly in areas where color temperature and color rendition are less important (i.e. warehouses, street lighting, security lighting). Metal halide is applicable in a wide range of commercial, industrial and municipal spaces and offers an excellent quality of light.

Studies show that people generally prefer to work and live in a white light environment, a fact that itself explains the dramatic shift toward metal halide.