For our test, we decided to go real-life instead of laboratory based, so we set our long-term Suzuki SV650X upright and level in a wheel chock on an unlit farm track. We swapped H4 bulbs and photographed how both dipped and main beam illuminated the track ahead. We placed cones every 15m to show how far the light travelled and took light readings, measured in lux, using a light meter at the first cone, 15m ahead of the bike. We also photographed the beam pattern against a sheet of wood in the workshop to show the spread and the colour and took a light reading here as well. We set the camera at the rider’s head position with a 55mm lens (very roughly what the eye sees) and used the same manually set ISO, shutter speed and aperture for every photo, so the differences you see in the photos are what your eye would see. As we were testing the bulbs, we were looking for certain criteria:
The light pattern should be crisply cut-off to prevent dazzling other traffic while still illuminating the road ahead and the near-side verge.
The distance ahead of the bike that the bulb illuminated the road, both for dipped and main beam.
How far the light travelled outward from a line directly ahead of the bike, illuminating the edges of both sides of the road.
The amount of light at the two measurement points and how it compares with manufacturer claims.