What is vertical illuminance for LED stadium lighting?
Vertical illuminance refers to the density of luminous flux falling on a vertical plane (usually facing the direction of the camera); it is also measured in lux (lx). Unlike horizontal illuminance (which illuminates the ground), vertical illuminance directly determines the brightness of athletes' faces, the fronts of their jerseys, and the sides of the ball. For television broadcasting, vertical illuminance is arguably even more critical than horizontal illuminance for the following reasons:
First, cameras primarily capture the front and side profiles of athletes. As athletes move, camera lenses remain focused on their bodies. If vertical illuminance is insufficient, athletes' faces appear dark and lose detail, making it difficult to distinguish jersey numbers or facial expressions.
Second, it determines image contrast and a sense of depth. Adequate vertical illuminance creates appropriate light and shadow, clearly defining human silhouettes and enhancing the three-dimensional effect.
Third, detail is essential for slow-motion replays. When reviewing moments like a goal or a foul, viewers want to see details—such as whether the ball crossed the line or if a player made contact—which relies on good vertical illuminance.
Fourth, it must meet broadcaster standards. International broadcasting organizations (such as the EBU and FIFA) explicitly require that vertical illuminance in the direction of the main camera be no less than 700 lux (with 1,000–1,500 lux typically recommended) and maintain high uniformity (minimum/average ratio ≥ 0.7).
Fifth, it must accommodate various camera angles. Stadiums utilize multiple camera positions beyond the main camera (located high in the midfield stand), including sideline cameras, cameras behind the goal, and drones. Lighting designs must ensure that vertical illuminance meets standards across all key viewing directions.
Therefore, professional stadium lighting design requires not only calculating horizontal illuminance but also simulating vertical illuminance using 3D software, typically by establishing multiple "camera points" for assessment. In practical application, vertical illuminance can be improved by increasing the number of luminaires, employing asymmetrical light distribution, and strategically positioning the fixtures.
