CHAPTER 7 — Red Eye/Golden Eye Correction

Figure-39Red eyes in your photos are unnatural and are caused by the light from a flash source bouncing off the back of the retina of the person in the photo. Generally speaking, this happens when the light of the flash enters the person’s eyes in a straight line [which is why red eye is most prevalent when people are looking straight into the camera]. Today’s camera’s have the flash located very close to the lens, increasing the likelihood that the people in your photos will have light from the flash enter their eyes directly and strike the back of their retinas. Needless to say, red eyes are color distortion, but it’s a distortion easily fixed by Perfectly Clear.

It starts with the Flash

Normally the pupil constricts when subjected to light. That is why a very small amount of light will reach the retina under normal lighting conditions. For this reason the eyes do not appear in natural conditions. With flash strobes, the red-eye effect appears because the pupil does not have the time to constrict so the retina is very well lit.

Figure40

Figure-40-2

Red Eye is related to the Angle of the light

Figure 41However the retinal region that is lit by flash must coincide with the one that is projected to the camera sensor in order for the red-eye effect to occur. This translates into the existence of a critical angle between the flash position, retina and camera lens, above which the effect does not occur. The value of this angle is approximately 3 degrees but if varies with the subject’s physiological characteristics as well as gaze angle.

Three parameters define this critical angle: the flash to lens distance of the camera, the camera to subject distance and the pupil dilations. Thus, the red-eye effect is most prevalent in photographs taken with compact digital still cameras and camera-enabled cell phones where the flash is normally very close to the lens. Additionally, the incidence of red eye increases with the subject distance and pupil size. The latter relates to the amount of light in the field of view of the subject. In daylight, when the pupil is almost as small as a pinhead the red-eye effect appears very scarcely. Conversely, the pupil is dilated in dark environments so the chance of the effect to occur is high.

Red eye results from a specific limitation in camera design.

Tessera is the world leader in removing Red-Eye

Tessera purchased FotoNation in 2008. We’ve incorporated this automatic red-eye and golden-eye solution into Perfectly Clear. Tessera is a leader in providing mulitple solutions to the photo industry. Although their focus is on embedded solutions – red eye for example is embedded in over 80 million digital comeras – Athentech has arranged for this powerful algorithm to be used by you in the post processing world. The novel Tessera red-eye detection and removal process is protected by multiple patents. Tessera maintains a database of 20,000 images containing challenging red-eye photos. Its solution is run against this extensive database to improve detection and removal.

Athentech Imaging’s intensive testing of multiple red-eye solutions resulted in Tessera’s being chosen because:
1. their solution automatically detected the highest percentage of true positive red-eye circumstances
2. While generating the lowest false positives
3. the fastest speed of detection and correction
4. the wide range of eye problems (both red-eye and golden-eye) it addresses
5. the fact that the corrected images are realistic and life-like in retaining the highlights on the eyes.

Athentech Imaging’s testing showed the automatic detection to be within the 80 percentile of accuracy.

The eyes and Red Eye

Red & golden eye is the result of a camera limitation and is an obvious color distortion that must be removed to reproduce your original experience. Better matching the original image in the mind’s eye requires accurate colors, exposure and requires your eyes seeing an accurate replication of the eyes of the subjects in your photo. Photo Accuracy demands Real Color.

The Red Eye Correction in Perfectly Clear is designed by Tessera to remove the red-eyes and reproduce photos with true, accurate color … Real Color. Perfectly Clear overcomes your camera’s limitation of red eyes in your photos, a very common problem of digital cameras shooting in low lighting conditions. The results are Accurate Photos that match the original image in the mind’s eye and serve to preserve Precious Memories perfectly. Accurate Photos are Superior Photos and science shows superior photos have the greatest emotional impact with viewers.