Choosing a rear-facing camera for close passes

Close passes happen behind you. That single fact rules out most of the advice written about cycling cameras, which is really advice about filming yourself descending nicely. What follows is what matters when the purpose is documenting a vehicle that you never saw coming.

Resolution matters less than you think. Until it doesn't.

For establishing that a pass happened and roughly how close it was, 1080p is genuinely sufficient. Where resolution becomes decisive is plate legibility, and there the binding constraint is usually not the sensor. It is motion blur and compression.

A plate is legible when enough pixels land on it, sharply, for at least one frame. A 4K camera with a slow shutter in poor light and an aggressive bitrate will produce a smeared, blocky plate. A well-exposed 1080p frame at a fast shutter can read cleanly. If a camera lets you bias toward shutter speed, that will do more for plate reads than doubling the pixel count.

Field of view is a genuine trade-off

Ultra-wide lenses capture more of the scene and make the overtaking vehicle look further away than it was. Narrower lenses put more pixels on the vehicle and make distance estimation more tractable, at the cost of losing things at the edge of frame.

For clearance measurement, what matters more than the number is that the field of view is known and stable. Any pixels-to-metres calculation depends on the lens geometry, so a camera that quietly changes its effective FOV between modes, or applies variable digital stabilisation crop, makes the measurement harder. Pick a configuration and leave it alone.

The specifications nobody prints on the box

• Loop recording that actually loops. The incident you want is the one you were not expecting. Continuous recording with automatic overwrite beats any manual trigger.
• Battery life at your real ride length. Quoted figures assume screen off, no GPS, mild temperature. Assume meaningfully less in winter.
• Mount rigidity. Seatpost mounts vibrate. Vibration means motion blur, and motion blur is what costs you the plate. A rigid mount is worth more than a sensor upgrade.
• Timestamp and GPS. Onboard GPS is ideal. Failing that, a camera whose clock you can set accurately, paired with a bike computer track you can align afterwards.
• Accessible files. Removable card or fast USB beats a proprietary app that transcodes over Bluetooth. If getting footage off the camera is painful, you will stop doing it.

Radar units and cameras solve different problems

Rear radar is excellent at telling you something is approaching, which is a live safety benefit a camera cannot offer. It is not evidence: it does not identify a vehicle or record a clearance. Several riders run both, and the combination is genuinely good: radar for awareness in the moment, camera for the record afterwards.

Position, and the boring conclusion

Seatpost mounting is the most common answer and works, provided the mount is rigid and a saddlebag is not clipping the frame. Helmet mounting gives a higher, more stable viewpoint and turns with your head: useful for context, worse for consistent measurement, because the geometry changes every time you look around. If you care about clearance numbers, a fixed mount on the bike beats a mount on you.

The boring conclusion: the best camera for this is the one that is charged, rigidly mounted, recording continuously, with the clock set correctly. Every rider who has tried to report an incident has at some point discovered the flat battery, the full card, or the clock still on factory time. The specification sheet is not usually what beat them.