1 Last Revised August 2015 Luminance Ratios Luminance Ratios - PDF document

Vision Lighting Ergonomics The right lighting for you!  Light enters eye & passes through: iris retina cornea aqueous humor pupil Troy Collins, BSc lens Ergonomics Advisor vitreous humor Workplace Health Eye Muscles Age-Related Changes  Ciliary muscles  Humors fill with debris control lens shape – “Floaties” – Scatters light in eye  Iris controls amount  Lens becomes more Extra ocular ciliary of light iris muscles muscles opaque  Need more light  Extra ocular muscles control eye  More susceptible to glare movement Illumination & Luminance Recommended Illumination Levels  Depends on age and the task  Luminance = light  Illumination = Light falling on a surface reflected or emitted – Traditional office tasks (paper-based): 500-750 lx from the surface – Computer workstations (mixture of computer and paper): 300-500 lx About same – Match light levels brightness – Some scenarios may require less light  E.g. negative polarity screens Images courtesy of CCOHS – Can be achieved with supplemental task lighting luminance ratios…  Must bear in mind 1 Last Revised August 2015

Luminance Ratios Luminance Ratios  Ratio of amount of light  Want balance of light coming from main task  High luminance ratios cause pupils High luminance Low luminance area to secondary and to dilate and constrict continuously Moderate luminance other areas, for – Eye fatigue, discomfort, headaches example:  Can also wash out details – Computer screen : paper – Too much light documents – Dispersion of light in eyes – Computer screen : window behind Glare Glare Sources: Direct  Discomfort glare -causes discomfort only  Direct-shining directly into the eye  Disability glare -causes reduction in visual – Windows performance – Bright light fixture – Poorly adjusted task  Blinding glare -makes it difficult to see lamp – E.g. bright headlights Image adapted from CCOHS Glare Sources: Indirect Glare Control  Indirect  Avoid direct view of light bulbs in design – Reflected from a  Adjust task lighting not to shine into eyes or onto surface screen  Desk  Wall  Floor  Computer screen Power on Power off Image courtesy of CCOHS 2 Last Revised August 2015

Glare Control Glare Control  Matte finishes  Avoid task light being too bright  Partitions  Window blinds  Create balanced brightness  Windows to side Personal Control Glare Control  Adjust the monitor contrast and  Dual monitors: same  Peaked or brimmed brightness to comfortable levels screen brightness hat  Eliminate / control glare – Preferably white screen – Minimize upward screen tilt with black characters – Screen perpendicular to window  Not as good for detail,  Practice the 20/20/20 Rule : though – every 20 minutes – stare at an object 20 feet away – for 20 seconds  Get your eyes checked at least every 2 years For More Information Visit our Ergonomics Page on the POD http://pod/empwell/ohsc/injprev/pages/Default.aspx 3 Last Revised August 2015