On Tue, 11 Aug 2009, Alan Gresley wrote >1. The 96px and 72pt boxes are the same size with a 96 DPI setting for >the monitor. > A point is 1/72 of an inch. Screen dpi's only purpose is to translate a measurement in inches to pixels.
pixels = inches * screen dpi It's as simple as that. Whenever _anything_ is specified in inches for display on a screen then this is the equation that programmers use to translate inches to pixels. (72 pts/ 72) = 1 inch 1 inch * 96 dpi = 96 pixels http://www.emdpi.com/screendpi.html >2. The 100px and 75pt boxes are the same size with a 96 DPI setting on a > monitor (75 pt/72) * 96 = 100 px >but also they are exactly 1 inch (using a ruler) in height and >width. > Only because you have a screen physical pixel density which happens to give you 1 inch. They are certainly not 1 inch on my screen. > >3. When the DPI setting is changed to 120 DPI, the boxes using pts >become 125% of their size at 96 DPI. > (75 pt/72) * 120 = 125 px i.e. 125% of 100 >4. The boxes using pixels are the same size and the box of 100px at >either 96 or 120 DPI still equals exactly 1 inch (using a ruler) in >height and width. > Try accurately measuring inches on a CRT with a curved screen, with the drawing surface separated from your ruler by a thick piece of glass, to say nothing of getting an undistorted image after playing with the 17 different CRT screen adjustments. Measuring inches on a screen is futile - and didn't suddenly become sensible because we changed from CRT to LCD. A screen is not a piece paper. >My question to you is why a box of 100px equals a inch measured by a >ruler and not what I expected 96px? > Don't understand the statement. >BTW, I thought the higher DPI setting would make the text smaller. I now >discover the reverse is true where the text and chrome of the browser is >larger. > The equation again, which is true for all inch length measurements on a screen pixels = inches * screen dpi Increase screen dpi and you increase pixels Also there seems to be view that screen dpi can only be 96 or 120. Screen dpi can be adjusted in the Control Panel by small steps between 19 dpi and 480 dpi. The elastic ruler. http://www.emdpi.com/screendpi.html -- Richard Mason http://www.emdpi.com ______________________________________________________________________ css-discuss [cs...@lists.css-discuss.org] http://www.css-discuss.org/mailman/listinfo/css-d List wiki/FAQ -- http://css-discuss.incutio.com/ List policies -- http://css-discuss.org/policies.html Supported by evolt.org -- http://www.evolt.org/help_support_evolt/
