Flicker in floodlighting: TV, slow motion and video

The flicker factor states in percent how strongly the brightness on a plane fluctuates during a full cycle. Whether the picture visibly flickers depends on the modulation of the light, the mains frequency and the frame rate of the camera. According to UEFA, a flicker factor below 3% usually causes no problems in slow motion up to 300 frames per second.

The UEFA Stadium Lighting Guide 2023 gives these maximum values for the average and the single value:

• Elite level A: below 3% on average, below 3% as a single value
• Level A: below 5%, below 5%
• Level B: below 12%, below 15%
• Level C: below 20%, below 30%

For televised hockey, the FIH guide of 2020 gives a maximum of 5% in category TV1 for top international hockey, 15% in TV2 and 30% in TV3. A reliable value therefore depends on the sport, the competition and the camera operation.

The DFL requires 1,600 lx and 1,200 lx in camera direction for the Bundesliga and 2. Bundesliga, and a system that meets the requirements of media productions. Details are set out in the media guidelines. The 3. Liga statute sets 800 lx Ecam on average, and new systems should reach 1,200 lx. Neither text gives a flicker value of its own.

You should therefore clarify early with the league, the association and the production company which value applies to your facility. The association guide from the football associations of Saxony, Saxony-Anhalt and Thuringia also names flicker-free light as a feature of good lighting, and as necessary for slow-motion footage.

As a rough guide, UEFA gives below 1% for LED luminaires, although the value depends on the LED driver. For high-intensity discharge lamps (HID) it gives below 3% with an electronic ballast, 8 to 20% with a magnetic ballast on three phases and 30 to 50% on a single phase. According to UEFA, existing systems can usually be retrofitted with electronic ballasts.

The stands count too: if only the pitch is flicker-free, the spectator area in the background of high-frame-rate recordings can still flicker. UEFA therefore recommends also checking the lighting of the spectator areas.

The UEFA and FIH guides give values for television broadcasts, not for phone videos or club streams. For video recordings of training, licht.de writes that no special requirements need to be observed and that standard-compliant general lighting is usually sufficient.

Because the frame rate also decides whether the picture flickers, it is best to test with your own camera and in the mode you will use later, including in slow motion. If you plan regular broadcasts, say so in your enquiry. For television pictures, the vertical light in camera direction also counts, and you should plan for it early.

UEFA has vertical measurements taken at a height of 1 m at six positions in two directions, i.e. at twelve points, by a qualified technician with a measuring device calibrated every year. The FIH requires measurements at every point of the measuring grid. These questions help in planning:

• Which flicker factor applies to the league, competition or production?
• Does the value refer to the measured system or only to a single luminaire?
• Was the association's measuring procedure applied?
• Are spectator areas and ancillary areas taken into account if they are in the picture?

Watch the metric: the EU Ecodesign Regulation limits the values Pst LM and SVM at full load for LED light sources, and the SVM limit does not apply to light sources intended for outdoor applications. These are different metrics from the flicker factor that UEFA and FIH require.