Reading about the 400 W Phillips Mastercolor I got the impression that the vertical bulb is designed to be in a fixture with reflector casting light in a downward direction. But it was a bit confusing to me. Is my interpretation right here? If so then it wouldn't be that useful as a bare bulb in a vertical grow.
This has me confused also. there's much discussion in this thread about using vertical lamps in horizontal reflectors. If you ask me, thread should not be allowed to get this large. Over 300 pages of arguing and very little actual information.
The lamp orientation has nothing to do with how the reflector casts the light. There are flood lights that are meant to cast light a primarily horizontal plane that use either a horizontal lamp or a vertical lamp. There are also downlight fixtures that position the lamp either horizontally or vertically. The lamp orientation within the fixture is what determines which lamp design you use - if the long axis of the lamp is parallel to the ground, then you need a horizontal lamp. If the long axis is at right angles to the ground, then a vertical lamp is needed. There are also some vertical lamps that are designed for base up orientation, and others that are for base down. "Universal" lamps can be used in any orientation.