The red-eye effect in photography is the common appearance of red pupils in color photographs of eyes. Photography (fә'tɒgrәfi or fә'tɑːgrәfi (from Greek φωτο and γραφία is the process and Art of recording pictures by means of capturing Red is any of a number of similar Colors evoked by light consisting predominantly of the longest wavelengths of Light discernible by the human eye in the wavelength The pupil is the hole that is located in the center of the iris of the eye and that controls the amount of light that enters the Eye. A photograph (often shortened to photo) is an Image created by Light falling on a light-sensitive surface usually Photographic film or an electronic Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain It occurs when using a photographic flash very close to the camera lens (as with most compact cameras), in ambient low light. A flash is a device used in Photography that produces an instantaneous flash of artificial Light A point-and-shoot camera, also called a compact camera, is a Still camera designed primarily for simple operation Red-eye effect appears in the eyes of humans and animals that have no tapetum lucidum, hence no eyeshine, and rarely in animals that have a tapetum lucidum. The tapetum lucidum ( Latin: "bright tapestry" plural tapeta lucida) is a layer of tissue in the Eye of many Vertebrate animals that The tapetum lucidum ( Latin: "bright tapestry" plural tapeta lucida) is a layer of tissue in the Eye of many Vertebrate animals that The red-eye effect is a photographic effect, not seen in nature.
Contents |
Causes
Because the light of the flash occurs too fast for the pupil to close, much of the very bright light from the flash passes into the eye through the pupil, reflects off the fundus at the back of the eyeball (see diagram in Eye), and out through the pupil. Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 The pupil is the hole that is located in the center of the iris of the eye and that controls the amount of light that enters the Eye. The fundus of the Eye is the interior surface of the eye opposite the lens, and includes the Retina, Optic disc, Macula and Eyes are organs that detect Light, and send signals along the Optic nerve to the visual areas of the brain The camera records this reflected light. The fact that the reflected light is red often is attributed to the ample blood supply of the retina and/or chorium, but this is incorrect. The red-eye effect is due to the color of the fundus, which is due to melanin, a pigment, principally located in the retinal pigment epithelium (RPE). Melanin is a class of compounds found in the Plant, Animal and Protista kingdoms, where it serves predominantly as a Pigment. In Biology, a pigment or biochrome is any material resulting in Color of plant or animal cells which The retinal pigment epithelium ( RPE) is the Pigmented cell layer just outside the neurosensory Retina that nourishes retinal visual cells and is firmly
Although in many animals the RPE is black, in humans it is brown[1]. Red-eye effect is more pronounced in people and animals with grey or blue eyes, and in children. Eye color is a Polygenic trait and is determined by the amount and type of Pigments in the Eye 's iris. In both groups, all tissues of the eye have relatively less melanin. In a pale eye, and in a child's eye, not only does the iris have less melanin to stop stray light from passing through it, but also the retina and choroid have less melanin to absorb stray light that enters the eye. The vertebrate retina is a light sensitive part inside the inner layer of the Eye. The choroid, also known as the choroidea or choroid coat, is the vascular layer of the Eye lying between the Retina and the Sclera The role of melanin in red-eye effect is most clearly seen in animals with heterochromia: only the blue eye displays the effect. In anatomy heterochromia refers to a difference in Coloration usually of the iris but also of Hair or Skin. The effect is still more pronounced in humans and animals with albinism. Albinism (from Latin albus, "white" see extended etymology) is a form of hypopigmentary Congenital disorder, All forms of albinism involve abnormal production and/or deposition of melanin.
Red-eye effect is seen in photographs of children also because children's eyes have more rapid dark adaption: in low light a child's pupils enlarge sooner, and an enlarged pupil accentuates the red-eye effect. In ocular physiology adaptation is the ability of the Eye to adjust to various levels of darkness and light
Similar effects
Similar effects, some related to red-eye effect, are of several kinds:
- In many flash photographs, even those without perceptible red-eye effect, many animals' pupils display eyeshine. An odd-eyed cat is a Cat with one Blue Eye and one Green, Yellow or Brown eye The tapetum lucidum ( Latin: "bright tapestry" plural tapeta lucida) is a layer of tissue in the Eye of many Vertebrate animals that Although eyeshine is an unrelated effect, animals with blue eyes may display the red-eye effect in addition to eyeshine (see Tapetum lucidum). The tapetum lucidum ( Latin: "bright tapestry" plural tapeta lucida) is a layer of tissue in the Eye of many Vertebrate animals that
- Numerous diseases of the eye cause a "white-eye effect" instead of the expected red-eye effect (see Leukocoria). Leukocoria (also leukokoria) is an abnormal white reflection from the Retina.
- A related effect, red reflex, is seen in fundoscopy; unlike the red-eye effect, it is not a photographic effect. The red reflex refers to the reddish-orange reflection from the Eye 's Retina that is observed when using an Ophthalmoscope or Retinoscope from The ophthalmoscope (or funduscope) is an instrument used to examine the Eye.
- In photographs recorded with infrared-sensitive passive (non-IR emitting) equipment, the eyes (not only the pupils) usually appear very bright. Infrared ( IR) radiation is Electromagnetic radiation whose Wavelength is longer than that of Visible light, but shorter than that of This is due not to reflection, but to radiation of core body heat in the form of infrared light (see Night vision). Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy Night vision is the ability to see in a dark environment Whether by biological or technological means night vision is made possible by a combination of two approaches sufficient
Photography techniques for prevention
The red-eye effect can be prevented in a number of ways.
- Using bounce flash in which the flash head is aimed at a nearby pale coloured surface such as a ceiling or wall or at a specialist photographic reflector. This both changes the direction of the flash and ensures that only diffused flash light enters the eye.
- Placing the flash away from the camera's optical axis ensures that the light from the flash hits the eye at an oblique angle. The light enters the eye in a direction away from the optical axis of the camera and is refocused by the eye lens back along the same axis. Because of this the retina will not be visible to the camera and the eyes will appear natural.
- Taking pictures without flash by increasing the ambient lighting, opening the lens aperture, using a faster film or detector, or reducing the shutter speed.
- Using ambient light and then
- digitally post-processing the image to increase its brightness, or
- Pushing the film development to increase the apparent film speed
- Utilising red-eye reduction capabilities built into many modern cameras. In Photography, push printing and push developing refer to a process where a picture is printed as if it were a Film speed higher than intended by These precede the flash with a series of short, low-power flashes triggering the iris to contract.
- Having the subject not look straight at the camera, instead look at the photographer's shoulder.
- Increase the lighting in the room so that the subject's pupils are more constricted.
- Some computer digital image editors have the ability to lessen the red eye by adding a hint of blue to it.
If direct flash must be used, a good rule of thumb is to separate the flash from the lens by 1/20 of the distance of the camera to the subject. For example, if the subject is 2 metres (6 feet) away, the flash head should be at least 10 cm (4 inches) away from the lens.
Professional photographers prefer to use ambient light or indirect flash as the red-eye reduction system does not always prevent red eyes, for example if people look away during the pre-flash. In addition, people do not look natural with small pupils, and direct lighting from close to the camera lens is considered to produce unflattering photographs.
Red-eye reduction techniques will be less effective when photographing people with dilated pupils.
Photography techniques for removal
Various graphics editing software packages have functions to remove red eyes from digital photographs. A raster graphics editor is a Computer program that allows users to paint and edit Pictures interactively on the computer screen and save them in one Some have automated this process, and can apply it to many photos at once. Red-eye removal is also built into many popular consumer programs like Microsoft Windows Vista Photo Gallery, Apple's iPhoto and The Gimp. Windows Photo Gallery is a photo management tagging and editing tool that is included in Windows Vista. iPhoto is a software application made by Apple Inc exclusively for their Mac OS X operating system The GNU Image Manipulation Program, or GIMP, is a free Raster graphics editor used to process digital graphics and photographs The downside to fully automatic software-based red-eye removal is that it is only accurate to approximately 75%. [2]
External links
- BBC Home, Edited Guide Entry: Determination of Eye Color
- Photocritic.org: Red eye and how to avoid it
References
- ^ Coscas, Gabriel and Felice Cardillo Piccolino (1998). Retinal Pigment Epithelium and Macular Diseases. Springer. ISBN 0792351444.
- ^ Raimondo Schettini and Francesca Gasparini and Fadi Chazli: "A modular procedure for automatic red eye correction in digital photos","Color Imaging IX: Processing, Hardcopy, and Applications" 5293, 139-147. SPIE, 2003
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic