Yeah, chico, I suspect that they're less likely to install ugly lights in upscale neighborhoods, because people with clout will complain. I thought I heard somewhere that San Diego was switching to 100% sodium vapor streetlights to minimize the light pollution at Palomar, though.

Thanks for the explanation. LA probably used them to conserve power, but maybe, in some places, to assert it.

Chico, I think those yellow lights are sodium-vapor lights. They're used for street lighting where: you want to conserve power (they're relatively efficient); you don't care about pure white light and perfect color rendition; or you don't want to interfere with nearby astronomical observatories (obviously not relevant in LA, Griffith Park and Mt. Wilson notwithstanding).

After an optics lab session about holography many years ago, I also found out that they can be used for viewing holograms, because the energy is mostly at a single wavelength.

This is old stuff. I remember seeing photographs from another photographer, whose name escapes me, who took the photos at night and used a bunch of stobes to highlight objects, including moving ones. I believed these were referred to as "power photos" or something like that. Must have been 15 or 20 years ago, at least.

After a couple of riots in South Central LA, the city installed yellowish 'riot lights' in naughty neighborhoods. They cast a sickly orange glow like sunlight filtered through smoke from a forest fire. Unlike the cold, white cleaniliness of ballpark lights, these just said welcome to losertown.