punasilmäisyyttä

Punasilmäisyyttä, known in English as red-eye effect, is a common photographic phenomenon that occurs when a camera's flash is too close to the lens and illuminates the retina at the back of a subject's eye. The retina contains a rich blood supply, and the light from the flash reflects off the blood vessels, causing the pupils to appear red in the resulting photograph. This effect is more pronounced in dim lighting conditions when the subject's pupils are dilated, allowing more light to enter the eye and thus more light to be reflected back.

The appearance of red-eye can vary in intensity and hue depending on factors such as the individual's eye color, the angle of the flash, and the camera's flash-to-lens distance. While most commonly associated with human eyes, red-eye can also occur in animals, though their eye coloration may differ.

Several methods exist to prevent or correct the red-eye effect. Many cameras offer a "red-eye reduction" mode that fires a pre-flash or an LED light to cause the subject's pupils to constrict before the main flash fires. Alternatively, red-eye can often be removed or reduced using photo editing software after the photograph has been taken. This typically involves selecting the red areas in the eyes and adjusting their color and brightness.