![]() ![]() The same application on a WXGA resolution (for instance 1440x900) looks 'larger' than on a WUXGA resolution (1920x1200), displayed pixel by pixel. With a higher display resolution letters become smaller. In any other regular PC application letters and numbers are displayed by pixels depending the font size chosen in the application. Powerpoint and similar presentation tools display letters and numbers in relative size to the entire image area not pixel-dependent. viewing distance / 6" = 20m / 6 = 3,33m (depends on PC format) !!Ĭalculate with this Excel file, download here This matches the rule of thumb that the image height should be "max. With a given text height calculated by the maximum viewing distance (distance/500) and the known number of lines (vertical pixels) of the projected image, a necessary image height can be calculated.Ī maximum viewing distance of 20m gives a absolute minimum text height of 40mm (20,000 / 500 = 40)Ī preferred font size of Arial 10 results in a text height of 10 pixelsĪn image source (PC) with a format of WXGA (1280x800) results in 800 lines (vertical pixels)Ī text height of 40mm (equal to 10 pixels) demands a image height of 3200mm (10 lines = 40mm > one line = 4mm > 800 lines = 3200mm) Text with a font size of 10 pt (like Arial 10) results on a Windows display in a text height of 10 pixels. This results in a minimum letter and number hight of 5 arcminutes, there as 7 arcminutes are acknowledged for general good readability. Visual Lossīased on the rules of visual acuity letters and numbers should have at least five times the height of the minimum distance between two recognizable objects. The term "6/12" means that two objects with a separation of 1 arcminute at a distance of 12 meters can only be seen separately at a distance of 6 meters, the term "20/40" means equally that two objects with a separation of 1 arcminute at a distance of 40 feet can only be seen separately at a distance of 20 feet. If a person is tested for a visual acuity of 6/12 (or 20/40), she or he can differentiate two objects only at half distance. Normal visual ability means that a person who can see this clearly has a Distance Visual Acuity of 5/5 (Europe) or 6/6 (Britain) or 20/20 (US). ![]() This equals approximately an object distance of 1,5mm at a distance of 5 meters or 1,75mm at a distance of 6 meters (20 feet). With normal viewing abilities two objects can be just seen individually with an viewing angle of 1 arcminute (MOA). The distance visual acuity is the visual sharpness or clearness of human eye view. But with higher resolutions (HD) this often results in image sizes that are too large to be installed (ceiling height etc.). It represents a viewing angle of about 7 arcminutes (1 degree = 60 arcminutes).Ĥ) For good readable text with text sizes like 'Arial 10pt' the maximum viewing distance should be divided by 500 to get the necessary text height. For these circumstances a tighter rule can be used: dividing the maximum viewing distance by 500 to get the absolute minimum text height (the absolute minimum for good eyes). 20 arcminutes correspond to 1/200 of the viewing distance.ģ) With high resolution projection rule 1 and 2 result in a text height that is too large for a regular Excel display on a regular projection size. ![]() All details that are presented in native pixel resolution become smaller for 35 to 40 percent !Īlso the image height should be within the following range:ĭistance of farthest Viewer / 8 the text height should be at least 40mm.Ģ) The FAA (Federal Aviation Administration, USA) suggests for letters that must be very well readable (security messages) a letter size of at least 20 acrminutes (MOA) based on the human eye's characteristics: FAA Human Factors. This is an increase of about 35 to 40 percent. With formats like SXGA, SXGA+ and HD(1080) this changes because the screen height is not built by 768 pixels but by 1024, 10 pixels. Important: this rule evolved with the majority of projections in the format XGA (1024 x 768). ![]()
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