For stage and studio lighting, designers work ‘hands on ’. Commands can be called (or even shouted) to minions, and the effects of aiming, focusing, filtering and dimming luminaires are immediately visible and can be explored until the required effect is achieved. This is not possible for architectural lighting. The concept may be developed before the space has been built. Even when lighting is being proposed for an existing space, it usually is part of a larger scheme for renovation or renewal, so that the design situation will be different. The concept has to be developed in the mind, and then translated into a schedule of lamps and luminaires, locations and controls, which will then be negotiated, tendered, and installed. According to the type of installation, the designer may have some scope for onsite adjustments, but basically the success of the lighting design depends on the designer’s skill in devising a technical specification that delivers the design concept. Technical competence is an essential skill for architectural lighting designers.