The red-eye effect in photography is the common appearance of red pupils in color photographs of human eyes. It occurs when using a photographic flash at low lighting or at night. When a flash passes through the eyes and rebounds at the back of the eye, it causes a red reflex in an image, turning the subject's eyes red. The hue is mostly caused by a high concentration of blood in the choroid. The effect can also be influenced by the near proximity of the flash and camera lens. In children, a different hue red reflex, such as white or yellow, may indicate an illness. In animals, a similar effect could cause their eyes to change colors in photographs.
The effect can be avoided physically by instructing the subject to look away from the lens, increasing the brightness of the photographic location, or moving the flash further away from the lens, or digitally by using the red-eye correction option on digital cameras or by removing the effect in editing software. Scholars have developed a number of red-eye detection techniques to improve digital red-eye removal.
The red-eye effect occurs in the eyes of humans when a photography flash is used in low light or at night. [1] [2] The flash travels through the eyes and rebounds at the rear of the eye, turning the eyes red (red reflex) in a photograph. [3] [4] [5] [6] The main cause of the red color is the ample amount of blood in the choroid, which supports the back of the eye and lies behind the retina. [5] [7] [8] Melanin also plays a role in the effect, as individuals with less melanin, such as albinos, reflect more light. [5] The close distance of the flash to the camera lens can also have an impact, especially on cameras with built-in flash. [7]
The effect could also infrequently occur in only one eye of persons with cataracts or tumors, or it may be exacerbated by photographing subjects that are drunk. [2] [4] In children, if the red reflex is white, it may indicate retinoblastoma malignancy, [6] [9] whereas yellow color may indicate Coats' disease. If the effect is asymmetrical, it may indicate strabismus. [6] A similar reaction to the red-eye occurs in animals, turning their eyes different colors. [4]
Either physical or digital manipulation of the effect is possible. [8] The subject can turn away from the camera lens, the flash can be mounted on a hot shoe, or the lighting can be increased to make the subject's pupils more constricted. The effect could potentially be avoided by positioning the flash off the side of the camera or by pointing it away from the subject and toward a white solid surface to bounce the flash off of it. [3] [4] [7] The subject could also be photographed near a bright light source or in sunlight. To lessen the effect, the photographer might alternatively employ the fill flash technique. [7] The effect can be removed digitally by using red-eye correction. [8]
Digital cameras with red-eye correction can eliminate the effect by using flash lighting that fires rapidly and repeatedly just before a photograph is taken, which causes the subject's pupils to contract. [3] [7] Editing software can also eliminate the effect. [7]
Scholars have proposed a number of red-eye detection methods for digital red-eye correction. The red-eye detection algorithm developed by electronic engineers Seunghwan Yoo and Rae-Hong Park is composed of face detection, region-growing, and red-eye detection. Following the detection of the subject's face and eyes, the algorithm searches for red-eye regions, which are subsequently enlarged using the region-growing technique. They claim that pupil size calculation, pupil painting, and iris detection make up the red-eye correction that may then take place. [10] Computer scientists Xiao-Ping Miao and Terence Sim have proposed their technique for detecting red-eye by fusing subjects' flash and non-flash photos. [11] Scholars Tauseef Ali, Asif Khan, and Intaek Kim put forth an algorithm that, following facial recognition, grayscales the image before applying red-eye correction. [12] On the contrary, researchers Richard Youmaran and Andy Adler presented a method for improving the quality of videos with the red-eye phenomenon. They have stated that their method consists of two frames, the first shot under standard illumination with no infrared light and the second one using infrared light. [13]
A single-lens reflex camera (SLR) is a camera that typically uses a mirror and prism system that permits the photographer to view through the lens and see exactly what will be captured. With twin lens reflex and rangefinder cameras, the viewed image could be significantly different from the final image. When the shutter button is pressed on most SLRs, the mirror flips out of the light path, allowing light to pass through to the light receptor and the image to be captured.
A camera is an instrument used to capture and store images and videos, either digitally via an electronic image sensor, or chemically via a light-sensitive material such as photographic film. As a pivotal technology in the fields of photography and videography, cameras have played a significant role in the progression of visual arts, media, entertainment, surveillance, and scientific research. The invention of the camera dates back to the 19th century and has since evolved with advancements in technology, leading to a vast array of types and models in the 21st century.
A twin-lens reflex camera (TLR) is a type of camera with two objective lenses of the same focal length. One of the lenses is the photographic objective or "taking lens", while the other is used for the viewfinder system, which is usually viewed from above at waist level.
A flash is a device used in photography that produces a brief burst of light at a color temperature of about 5500 K to help illuminate a scene. The main purpose of a flash is to illuminate a dark scene. Other uses are capturing quickly moving objects or changing the quality of light. Flash refers either to the flash of light itself or to the electronic flash unit discharging the light. Most current flash units are electronic, having evolved from single-use flashbulbs and flammable powders. Modern cameras often activate flash units automatically.
Underwater photography is the process of taking photographs while under water. It is usually done while scuba diving, but can be done while diving on surface supply, snorkeling, swimming, from a submersible or remotely operated underwater vehicle, or from automated cameras lowered from the surface.
Canon EOS is an autofocus single-lens reflex camera (SLR) and mirrorless camera series produced by Canon Inc. Introduced in 1987 with the Canon EOS 650, all EOS cameras used 35 mm film until October 1996 when the EOS IX was released using the new and short-lived APS film. In 2000, the D30 was announced, as the first digital SLR designed and produced entirely by Canon. Since 2005, all newly announced EOS cameras have used digital image sensors rather than film. The EOS line is still in production as Canon's current digital SLR (DSLR) range, and, with the 2012 introduction of the Canon EOS M, Canon's mirrorless interchangeable-lens camera (MILC) system. In 2018 the system was further extended with the introduction of the EOS R camera, Canon's first full frame mirrorless interchangeable lens system.
The Canon EOS 20D is an 8.2-megapixel semi-professional digital single-lens reflex camera, initially announced on 19 August 2004 at a recommended retail price of US$1,499. It is the successor of the EOS 10D, and was succeeded by the EOS 30D in August 2006. It accepts EF and EF-S lenses and uses an APS-C sized image sensor.
An autofocus (AF) optical system uses a sensor, a control system and a motor to focus on an automatically or manually selected point or area. An electronic rangefinder has a display instead of the motor; the adjustment of the optical system has to be done manually until indication. Autofocus methods are distinguished as active, passive or hybrid types.
An eye examination, commonly known as an eye test, is a series of tests performed to assess vision and ability to focus on and discern objects. It also includes other tests and examinations of the eyes. Eye examinations are primarily performed by an optometrist, ophthalmologist, or an orthoptist. Health care professionals often recommend that all people should have periodic and thorough eye examinations as part of routine primary care, especially since many eye diseases are asymptomatic. Typically, a healthy individual who otherwise has no concerns with their eyes receives an eye exam once in their 20s and twice in their 30s.
A digital single-lens reflex camera is a digital camera that combines the optics and mechanisms of a single-lens reflex camera with a solid-state image sensor and digitally records the images from the sensor.
In photography and optics, vignetting is a reduction of an image's brightness or saturation toward the periphery compared to the image center. The word vignette, from the same root as vine, originally referred to a decorative border in a book. Later, the word came to be used for a photographic portrait that is clear at the center and fades off toward the edges. A similar effect is visible in photographs of projected images or videos off a projection screen, resulting in a so-called "hotspot" effect.
Fill flash is a photographic technique used to brighten deep shadow areas, typically outdoors on sunny days, though the technique is useful any time the background is significantly brighter than the subject of the photograph, particularly in backlit subjects. To use fill flash, the aperture and shutter speed are adjusted to correctly expose the background, and the flash is fired to lighten the foreground.
Leukocoria is an abnormal white reflection from the retina of the eye. Leukocoria resembles eyeshine, but leukocoria can also occur in animals that lack eyeshine because their retina lacks a tapetum lucidum.
Sony α is a brand of digital camera. This line has been active since 2006, building upon the Konica Minolta camera technologies, whose assets were acquired by Sony.
The following outline is provided as an overview of and topical guide to photography:
The red reflex refers to the reddish-orange reflection of light from the back of the eye, or fundus, observed when using an ophthalmoscope or retinoscope. The red reflex may be absent or poorly visible in people with dark eyes, and may even appear yellow in Asians or green/blue in Africans.
Most digital cameras support the ability to choose among a number of configurations, or modes for use in various situations. Professional DSLR cameras provide several manual modes; consumer point-and-shoot cameras emphasize automatic modes; amateur prosumer cameras often have a wide variety of both manual and automatic modes.
The Nikon D90 is a 12.3-megapixel digital single-lens reflex camera (DSLR) model announced by Nikon on August 27, 2008. It is a prosumer model that replaces the Nikon D80, fitting between the company's entry-level and professional DSLR models. It has a Nikon DX format crop sensor.
The Canon EOS 500D is a 15-megapixel entry-level digital single-lens reflex camera, announced by Canon on 25 March 2009. It was released in May 2009. It is known as the EOS Kiss X3 in Japan, and as the EOS Rebel T1i in North America. It continues the Rebel line of mid-range DSLR cameras, is placed by Canon as the next model up from the EOS 450D, and has been superseded by the EOS 550D (T2i).
The Canon EOS 7D Mark II is a professional digital single-lens reflex camera made by Canon. It was announced on September 15, 2014 with a suggested retail price of US$1,799. It features a 20.2 effective megapixel APS-C CMOS sensor, Full HD video recording at 60 fps, 10.0 frames per second continuous shooting, a 100% accuracy viewfinder that offers 1× magnification. It also features a 65-point auto-focus system, a built-in Speedlite transmitter and a new 150k RGB pixels + IR metering sensor. It was preceded by the Canon EOS 7D.