Sunglint

Sunglint is the mirror-like reflection of sunlight from a water surface. It occurs when the angle of incidence equals the angle of reflection, causing a bright patch or streak of high radiance that travels across water as the observer or sun moves. The effect is governed by surface roughness, wind-driven waves, the sun’s altitude, viewing geometry, and the optical properties of water. Calm, smooth surfaces tend to produce more pronounced glints than rough, choppy seas.

In remote sensing and aerial photography, sunglint can saturate optical sensors and obscure spectral features used to characterize water quality, plankton, and suspended matter. Because glint depends strongly on sun–sensor geometry, it moves with the sun and camera position, often creating a bright region that complicates radiometric correction. Glint is typically mitigated by masking, specialized processing, or choosing sensor geometry that minimizes reflective angles.

From a physical perspective, sunglint contains information about surface roughness and wind conditions; some models relate the distribution of surface slopes to wind speed and fetch, allowing indirect estimation from glint patterns. Practically, it provides a calibration reference but poses a challenge for quantitative ocean color retrievals and coastal studies unless properly addressed.

Beyond science, sunglint is a common source of glare in boating and photography, reducing visibility and causing discomfort. Mitigation strategies include polarization, anti-glare devices, choosing times of day with less direct reflection, and data processing techniques to mask or correct glint in imagery.