Jay8: What you describe is a 'quartz restrike' option, usually on hi-bay HID fixtures, to provide illumination while the HID lamp is re-striking from a power interrupt.
Re-reading the OP, and his second comments, it sounds more like he's looking for some type of 2-level lighting that uses two different light sources. I've seen & installed 2-level lighting, but it was a single light source (MH).
