Since Gilles has mentioned “doped” metal halide lamps, I’m guessing some folks may be wondering just what that means, and while some may wonder what is the difference between metal halide and mercury vapor.[attachment file=“26311”]
The simple answer to the second question is that metal halide is a “new and improved” variety mercury vapor. Metal halide lamps are mercury vapor lamps doped (or dosed in some of the literature) with metal halide additives that modify the spectrum of the output. Gallium “doped” lamps have peak output in the 400-420nm range. I think it is safe to say that the Olec L900/L1250 are gallium doped, as are Gilles’s and Rafael’s based on the spectral charts they posted. [attachment file=26312]
The iron doped lamps include the Olec L1261/L1281. [attachment file=26313]
I’m guessing that the Olec L902/L1252/L1282 might be a combination.
If you are using a plateburner and don’t know what kind of lamp you have, one way to make a good guess is from the color of the light. A slight greenish hue indicates that it is probably plain mercury vapor. A blueish hue indicates iron-doped. And a purpleish hue indicates gallium-doped. At least that’s what I read somewhere. 
