Contrast (vision) - Factbites

Contrast (vision) - Factbites
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Topic: Contrast (vision)

Note: these results are not from the primary (high quality) database.

In the News (Sat 26 Dec 09)

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	LaserMyEye :: Encyclopedia :: 20/20, 20/30, 20/40 etc.
		The complications patient who is puzzled by being told he has "excellent vision" when he does not see well needs to ask specifically for testing aimed at assessing vision quality, such as contrast sensitivity testing and wavefront aberrometry.
		One can have normal acuity and at the same time have vision quality defects such as double vision, poor contrast, night vision disturbances (starbursts, haloes, etc).
		In most places 20/40 is also "driving standard vision", that is, one who can read the 20/40 line on the eyechart meets the visual requirements to be given a driver's license.
	www.lasermyeye.org /encyclopedia/2020.html (397 words)

	Journal of Vision - Visual span: A sensory bottleneck on reading speed, by Legge, Lee, Owens, Cheung, & Chung
		Because most reading deficits in low vision are associated with losses in acuity, contrast sensitivity or field, our findings suggest that a reduced visual span is a key factor in limiting low-vision reading.
		Our findings are consistent with the view that reduction of the size of the visual span limits normal reading speed near the acuity limit, near contrast threshold, and in peripheral vision.
		For eccentricity, both declined in peripheral vision (group correlation =.98).
	www.journalofvision.com /2/7/279 (397 words)

	The Effect of Bilberry Nutritional Supplementation on Night Visual Acuity and Contrast Sensitivity
		A more recent investigation examined the effects of bilberry on whole field scotopic retinal threshold, mesopic contrast sensitivity, and dark adaptation rate, administering dosages of either 24 mg or 48 mg of anthocyanosides daily for four days and found no effect on night vision testing.
		The night vision tests used by previous investigators studying the effects of bilberry supplementation have included scotopic light thresholds, electroretinograms (ERGs), changes in the dark adaptation rate, scotopic perimetry, and mesopic contrast sensitivity.
		Contrast was calculated with the formula: C = Lmax Â Lmin/Lmax + Lmin, where Lmax = background luminance and Lmin = target letter luminance.
	www.pharmafort.com /AlternMedRev2000.htm (397 words)

	5w_Computer_Vision_syndrome.htm
		Computer images are generally less distinct than printed characters, may have perceptible flicker, and usually have less contrast between characters and the background on which they appear.
		After you're finished with the brightness, adjust the contrast to the highest amount you are comfortable with (this should be a very high level of contrast).
		Computer glasses and/or ergonomic adjustments should clear up your aches and pains.
	www.websystem2.com /articles/5w_Computer_Vision_syndrome.htm (397 words)

	Visual Disablilties: Low Vision
		Some people with low vision will change the settings in their operating system and/or browser to not only enlarge the text, but to increase the contrast of the text in relation to the background.
		People with low vision often benefit from higher contrast.
		Low vision is more common among the elderly, but it can occur in individuals of any age as a result of such conditions as macular degeneration, glaucoma, diabetic retinopathy, or cataracts.
	www.webaim.org /techniques/visual/lowvision (1139 words)

	handprint : color psychology
		Vision seems continually to isolate contrast or stimulation wherever it appears, as a primitive strategy to identify unusual (attention getting) features in the environment and bring them (advancing) to our attention.
		The extreme "violet" end of the spectrum also stimulates the red side of the r/g opponent contrast, so the hue perception appears to contain some red.
		Because the R cones are stimulated when we perceive violet or purple hues, we judge these to be similar colors — in the same way that yellow seems similar to green, because the G cones are stimulated by both colors.
	www.handprint.com /HP/WCL/color3.html (1139 words)

	15
		Schor, C.M. and Kees, M. (1981) Graphical and normative analysis of binocular vision by mini computer: a teaching aid and clinical tool.
		Schor, C.M. (1981) Direction anisotropies of pursuit tracking and optokinetic nystagmus in abnormal binocular vision.
		Investigative Ophthalmology and Vision Science 38 (3), 719-740.
	mach.berkeley.edu /cliff/cliff-cv.html (1139 words)

	PRIO - What is Computer Vision Syndrome?
		Characters on a computer screen, however, don't have this contrast, or well-defined edges.
		Until now, traditional eye exams for near vision have resulted in eyewear suited for reading printed material, not for viewing computer screens.
		Our eyes respond well to most printed material, which is characterized by its dense black characters with well-defined edges which contrast markedly from their light background.
	www.prio.com /consumers/problem.cfm (224 words)

	Contrast Medium - compare prices, reviews and buy at NexTag - Price - Review
		related searches:medium expressionist,high contrast cinema vision,medium format scanner,medium format film scanners
		DA-LITE 95571 High Contrast Cinema Vision Cinema Contour - Small to Medium
		Genuine leather construction Contrast lining and stitching Snap closure Two cash pockets Eight card slots ID window slot Zippered coin pocket Dimensions: W 5 1/2 in; H 3...
	www.nextag.com /contrast-medium/search-html (248 words)

	Jacob Nachmias Homepage
		Nachmias, J. Contrast discrimination with and without spatial uncertainty (2002) Vision
		Nachmias, J. Contrast modulated maskers: Test of a late non-linearity hypothesis.
		Nachmias, J. A template matching model of subthreshold summation.
	www.psych.upenn.edu /~nachmias/nachmi~1.htm (120 words)

	Vision and Eye Tests for Cataract
		For example, the contrast between the pavement and the sidewalk, which is the main cue that defines the edge of a curb, may typically be just a few percent.
		Glare disability is a reduction of the contrast of the retinal image caused by extraneous bright light sources present in the visual field.
		Pelli-Robson contrast sensitivity score of less than 1.5 is consistent with visual impairment and a score of less than 1.0 represents in visual disability.
	www.agingeye.net /cataract/cataracteyeexam.php (1744 words)

	Contrast Luminance Contrast Michelson Constrast Modulation Peak-to-Peak Contrast Weber Contrast
		Contrast (Luminance Contrast) is the relationship between the luminance of a brighter area of interest and that of an adjacent darker area.
		Simple Contrast values are often used in photography, to specify the difference between bright and dark parts of the picture.
		This definition is also called Weber Contrast, and is the most commonly useful one in the context of lighting.
	www.schorsch.com /kbase/glossary/contrast.html (164 words)

	Vision Series - darksky.org
		Contrast is sensed when the light gradient is coarse, or in other words the spatial frequency is low.
		It also has a contrast sensitivity function, the curve of which is reciprocal to spatial frequency.
		Once the point of contrast is stared at for too long without moving the position of our eyes, that point which was originally a point of change, now becomes static.
	www.darksky.org /VisionSeries/vs3-5.html (1014 words)

	Anomalous Colour Vision
		The perception of colour is not entirely that exhibited under standard laboratory conditions, as in the assessment of anomalous colour vision, but in nature is influenced by illumination, contrast, fatigue and other factors.
		Anomalous colour vision is usually a genetically determined normal state, predominantly in men since it is carried in the Y chromosome
		Colour blindness can also be the result of disease or poisoning, where it has no genetic basis, or due to other faults than those of the visual proteins.
	www.du.edu /~jcalvert/optics/colvisn.htm (1014 words)

	Webvision: Color Vision. by Peter Gouras
		Orientation selectivity, undoubtedly essential for form vision, could be based on either or both of these forms of contrast.
		Color and all vision are in a sense illusory depending only on messages that pass between millions of neurons that reside within the darkness of our skull.
		Physiology attempts to explain color vision by the responses of neurons.
	webvision.med.utah.edu /Color.html (8851 words)

	Effective Color Contrast - Designing for People with Partial Sight and Color Deficiencies - Lighthouse International - Lighthouse International
		Two colors that contrast sharply to someone with normal vision may be far less distinguishable to someone with a visual disorder.
		It is important to appreciate that it is the contrast of colors one against another that makes them more or less discernible rather than the individual colors themselves.
		Avoid contrasting hues from adjacent parts of the hue circle, especially if the colors do not contrast sharply in lightness.
	www.lighthouse.org /color_contrast.htm (8851 words)

	Machine Vision Guide - Lens Fundamentals
		Factors other than lens resolution can affect contrast.
		For example, with the lens operating at f/22 and allowing a geometric blur of two pixel widths, the DOF is 3.2 mm, which is four times larger.
		In optics, distortion is a particular lens aberration that causes objects to be imaged farther or closer to the optical axis than for a perfect image.
	www.mellesgriot.com /products/machinevision/lef_5.htm (1491 words)

	handprint : light and the eye
		The essence of this mammalian vision remains in the warm/cool color contrast.
		If we want to explain vision as the search for information about the world, then the most important fact is this: the visible spectrum represents the range of electromagnetic radiation that interacts with matter in the most complex and varied ways (at least 14 ways, to be exact).
		Vision is, so to speak, an incredibly specific form of touch bound to a three dimensional array of tiny, light sensitive molecules.
	www.handprint.com /HP/WCL/color1.html (1491 words)

	handprint : light and the eye
		The foveal photoreceptors are connected to specialized secondary cells — with "colorful" names such as midget ganglion and parasol cell — that group neighboring cells into center/surround receptive fields that sharpen edges and contrast based on the relative proportions of stimulation received by all the cells in a group.
		In mesopic vision the rod and cone outputs are pooled in shared nerve pathways, combining the scotopic and photopic curves and shifting the darkening hues toward bluish green.
		The idea that our perception of millions of colors depends on just three distinct color receptors is called the three color or trichromatic theory of color vision, first proposed in the 18th century.
	www.handprint.com /HP/WCL/color1.html (12155 words)

	Residual Binocular Interactions in the Striate Cortex of Monkeys Reared With Abnormal Binocular Vision -- Smith et al. 78 (3): 1353 -- Journal of Neurophysiology
		Binocular contrast summation was investigated in 21 neurons from the treated monkeys.
		Binocular interactions in individual V1 neurons were investigated in four macaque monkeys ( Macaca mulatta) reared with an
		Binocular interactions in V1 neurons of normal animals appear to largely reflect the linear combination of inputs from the
	jn.physiology.org /cgi/content/full/78/3/1353 (12155 words)

	module_11.htm
		These results support the hypothesis for an M pathway abnormality in dyslexia, and suggest that motion discrimination may be a more sensitive psychophysical predictor of dyslexia than contrast sensitivity.
		One hypothesis regarding the etiology of schizophrenia proposes that disruption of the dopaminergic innervation of the prefrontal cortex leads to an increase in dopamine (DA) transmission in subcortical regions.
		This hypothesis has been tested and results consistent with the hypothesis (and with a number of older reports) have been obtained.
	www.dendrites.com /module_11.htm (15812 words)

	The Streaming Serpent
		The association between the wind and the serpent is perhaps the oldest and most widespread in Mesoamerican history, in contrast to the other three elements.
		The priestess could then communicate with this Vision Serpent, this sacred vehicle carrying the soul of an ancestral king.
		In the sacred calendar, the day-sign of the serpent occurs under the presence of Chalchiuitlicue, the goddess of living waters.
	members.aol.com /vucubcaqix/serpent2.htm (994 words)

	Low Vision Defined - Lighthouse International
		Vision is a complex sense, encompassing the ability to perceive detail (acuity), color and contrast, and to distinguish objects.
		Low vision services are provided by specially trained professionals in a number of settings: hospitals, vision rehabilitation organizations, private optometric and ophthalmologic practices, and educational and university facilities.
		The adaptive process, in coordination with low vision services, is known as vision rehabilitation; its goal is to equip people who are visually impaired with the skills and confidence needed to function as independently as possible.
	www.lighthouse.org /low_vision_defined.htm (994 words)

	Peripheral Vision
		Vernier and contrast discrimination in central and peripheral vision.
		Relative roles of resolution and spatial interference in foveal and peripheral vision.
		Compound grating discrimination was measured in normal foveal and extrafoveal vision as well as in central vision of amblyopic subjects.
	www.bradford.ac.uk /acad/lifesci/optometry/research/projects/PeriVis.htm (1866 words)

	INTRODUCING 'OPTUS' COMPUTER SCREEN GLASS FILTER
		OPTUS uses an optimum light transmission of 55% so that while the glare is eliminated, contrast is also maintained.
		OPTUS is a premium quality, multi-layer coated computer screen glass filter that has been launched in the Indian market keeping in mind the health requirements of regular computer users.
		OPTUS has a conductive metal thin-film coating that effectively discharges the static field and blocks ELF, VLF and UV radiation so that a safer and healthier work environment is maintained.
	business.vsnl.com /amvindia (1866 words)

	RRTC:Information and Resource Referral Project
		although reduced central or reading vision is common, low vision may also result from decreased side (peripheral) vision, a reduction of loss of color vision, or the eye's inability to properly adjust to light, contrast or glare.
		Visual Acuity - Acuteness or clarity of vision which is dependent on the sharpness of the retinal focus, the sensitivity of the nervous elements, and the interpretative faculty of the brain.
		Low Vision - When ordinary eye glasses, contact lenses or intraocular lens implants cannot provide sharp sight, and an individual is said to have low vision.
	www.blind.msstate.edu /irr/def.html (797 words)

	Low Vision
		Low vision is not blindness, which is the absence of useful vision or light perception.
		Low vision refers to impaired vision that does not improve through medicine, surgery, or ordinary corrective lenses.
		Individuals with low vision find it difficult or impossible to do many everyday tasks.
	www.uic.edu /com/eye/PatientCare/EyeConditions/LowVision.shtml (144 words)

	Low Vision Services - Vision Rehabilitation Services - Vision Rehabilitation - VisionConnection
		A person who has low vision may also experience problems detecting contrast -- distinguishing between objects and their background, or between words on a page.
		Low vision, also known as partial sight, can result from an eye disease, accident or stroke.
		If you find that your low vision devices are no longer working, it's time to return for a new low vision exam.
	www.visionconnection.org /Content/VisionRehabilitation/VisionRehabilitationServices/LowVisionServices (552 words)

	Vision
		Provides information on vision science, vision testing technology, contrast sensitivity, and functional vision.
		Vision Education campaign to encourage yearly eye exams, as well as vision care education and media resources for the public and eye care professionals.
		Vision Research activities span topics in the areas of human visual sensing and electronic imaging.
	www.wolist.com /wo/health/senses/vision/vision.html (552 words)

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Topic: Contrast (vision)

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In the News (Sat 26 Dec 09)