Final answer:
The red eye effect is caused by the camera flash bouncing off the retina, which can be reduced with red-eye reduction mode. Adjusting the angle of incidence and using fill flash help prevent flash glare and properly expose photos.
Step-by-step explanation:
The red eye effect in photography occurs when the camera flash bounces off the retinal pigment and blood vessels of the eyes. This happens because the camera flash illuminates the eyes from close to the camera's lens, causing light to reflect back from the retina's rich blood supply. This effect is most common in low-light conditions when the subject's pupils are dilated. To reduce or avoid the red eye effect, many cameras have a red-eye reduction mode that pre-flashes to contract the pupils before the main flash.
To combat the reflective properties leading to both the red eye effect and flash glare in photography, the angle of incidence can be adjusted. For instance, if taking a photo of someone with glasses, you can tilt the glasses slightly to prevent the flash from reflecting directly back into the camera lens. Similarly, positioning the camera at an angle to reflective surfaces can prevent direct reflection. Using a fill flash technique can also counteract the challenges of backlit subjects by adding enough light to balance the foreground lighting with the brighter background. Underexposed photos lack light, while overexposed images have too much light, which can result in areas being 'blown out' or lacking in detail due to excessive brightness.