Why sunglasses fog, and what reduces it
Fogging is warm damp air meeting a cooler lens with nowhere to go. How the venting on SOA, DARA and NOA moves air across the back of the lens, and what airflow can and cannot do.
The cause
Fog forms when warm damp air from your face meets a lens that is cooler, and has nowhere to go. Running raises the temperature and humidity of the air right behind the lens. If that air sits still, it condenses.
Coatings are one answer. Moving the air is the other, and it is the one that keeps working after the coating has worn off.
SOA
SOA leaves a gap between the lens and the frame at both outer edges. Air pushed in behind the lens exits there instead of collecting. The temple arms are channelled, which gives it a second route out along the side of the head.
SOA has no adjustable nose pads, so the gap between lens and face is fixed by the frame geometry rather than set by the wearer.
DARA
DARA vents through a port at the upper outer corner of the lens. It also has adjustable nose pads, and raising them lifts the whole frame slightly off the face. That opens the gap between lens and face and increases the airflow across the back of the lens.
So on DARA the venting is adjustable. Set the pads low for a closer fit, higher when it is hot or humid.
The pads rotate about a fixed hinge. Raising them lifts the frame off the face, which widens the gap behind the lens and moves more air across it. Standoff in millimetres at both pad positions has not been measured.
NOA
NOA works the other way round. The windshield profile reduces how much air reaches the eye at speed, which is a cycling problem rather than a fogging one. Wind in the eye causes tearing and fatigue on long descents.
NOA also has silicone temples and takes a replaceable lens, but it has no adjustable nose pads.
Limits
Airflow reduces fogging. It does not eliminate it. Standing still in high humidity after a hard effort will fog any lens, and no frame design prevents that. What venting changes is how quickly it clears once you are moving again.
Venting by model
| Model | Venting | Adjustable | What it addresses |
|---|---|---|---|
| SOA | Side exhaust at both outer edges, plus channelled temple arms | Fixed | Fogging |
| DARA | Port at the upper outer corner, plus adjustable standoff | Yes, via the nose pads | Fogging |
| NOA | Windshield profile | Fixed | Wind in the eye |
Common questions
Will these fog up?
Less than a sealed frame, and they clear faster once you are moving. SOA vents at the sides and through the temples. DARA vents at the upper corner and lets you raise the frame off the face. Nothing prevents fogging entirely in high humidity.
Do they have an anti-fog coating?
No. The venting is mechanical, which means it keeps working for the life of the frame rather than wearing off the way a coating does.
