On Sun, 15 Mar 2009, Tim Climis wrote >I gradually learned through online reading that that was not the right way to >do it, and stopped, but I've never been able to figure out why it's wrong in >the first place. > One reason is that points are inches and some people who write about these topics just don't understand how an Operating System differentiates between inches on paper and inches on screen. In computer typography a point is 1/72 of an inch so anything measured in points is actually measured in inches.
In "Eric Meyer on CSS" he says "There is no clearly defined mapping between pixels and the physical world. How many pixels should there be per inch?". Nonsense. Of course there are completely defined mappings of inches to pixels. Programmers have been writing text editors and word processing programs for years where they clearly map font size in points (inches) to pixels on screen. When printing the programmer knows the size of the piece of paper, but when putting text on screen the programmer has no way of reliably, or accurately, knowing the size of your screen so there had to be a standard way of converting lengths specified in inches into lengths in pixels, and this is done by using 'screen dpi', the value of which, in Windows, we can change in the Control Panel Length in inches * screen dpi = Length in pixels So if something is specified as one inch long and screen dpi is set, via the Control Panel, to 102 dpi (my current setting) then: 1 * 102 = 102 pixels. Unfortunately people then put their ruler up to the screen and find it's not one inch on their ruler so incorrectly conclude that "There is no clearly defined mapping between pixels and the physical world'. Add to that the fact that the actual physical number of pixels per linear inch (determined by the monitor manufacturing process) is specified as a number of dpi it's hardly surprising that there is confusion and inches get a bad press. After all that, browsers (as opposed to the Operating System) don't treat inch measurements in a completely consistent manner why be surprised? They don't seem to treat many other quantity's in a consistent manner either e.g. "Don't use pixels because ...." If inches are going to get a bad press then authors should do so for the right reasons, not the spurious reasons so often seen. >It seems that this whole font sizing mess boils down to the fact that "pixel" >is not a standardized unit of measure. one pixel on my monitor is a different >size from one pixel on your monitor. > The word "standard" means what here? The CSS spec tries to define a "standard pixel", and talks rubbish. Actually one pixel on your monitor is different to another pixel on your monitor at different times. If, say, you usually operate at 1280 * 1024 and then switch to 1024 * 768 then 20% of pixels have 'disappeared' both horizontally and vertically, but the whole screen is still filled. Pixels have changed their size. -- 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/
