A CPL (or Circular Polarization) filter is an attachment you place over the lens that reduces harmful radiation and annoying reflections. A CPL filter is particularly capable of blocking light from angled angles. You usually place a dashcam behind an angled windscreen, which can sometimes cause reflections from the dashboard to appear in the videos. A CPL filter can block these reflections to a large extent so that the image quality improves a lot.

Besides preventing annoying reflections, the CPL filter also protects the lens from harmful radiation. Prolonged filming in high sunshine can eventually cause damage to the lens and image sensor, for the same reason you can't look at the sun for too long. Using a CPL filter can therefore significantly extend the life of the dashcam - especially in sunny areas.

Polaroid sunglasses

Circular Polarisation is the same technique used in Polaroid sunglasses. These sunglasses prevent a lot of reflections, making vision a lot better and more pleasant, they are therefore ideally suited for while driving. However, a CPL filter also blocks a lot of light, making the image darker. It is advisable to remove the CPL filter at night or in cloudy conditions so that the image does not become too dark; after all, you do not put on sunglasses at night.

For this reason, using a CPL filter can sometimes be quite impractical, which is also why by no means all dashcams support a CPL filter. Despite the fact that it sometimes benefits image quality and durability, you probably don't feel like removing the CPL filter every night.

Mounting and other filters

Depending on the type of dashcam, the CPL filter is placed over the lens in different ways. With Viofo, the CPL filter is square and is slid over the lens using a click system. Mini and Kenwood's CPL filters are magnetic and thus ‘stick’ to the lens. With LUKAS and Qvia, the CPL filter is rotated onto the lens. The magnetic and twist mounts are the most practical because the CPL filter needs to be rotated a certain way to achieve the best result. Despite the fact that the square filter has a round lens, turning it is a bit more difficult.

Besides CPL filters, some dashcams from LUKAS and Qvia are also equipped with a UV filter as standard. This additionally protects the lens from harmful UV radiation. The UV filter has no negative effect on image quality and the optional CPL filter itself can be rotated on top of the UV filter so that the lens is protected in two ways.