For Jim's sample, I would prefer "pixel density" of 20.84 E6 m^-2; keeping the prefix "milli" out of the denominator, retaining only the four original significant digits, and avoiding confusing of the "entity" (pixel) with the SI unit (m^-2), even though base 10 exponential notation (E6) is not universally established.
---- Original message ---- >Date: Fri, 14 Jan 2011 11:39:48 -0600 >From: "James R. Frysinger" <j...@metricmethods.com> >Subject: [USMA:49516] Re: Screen size conundrum >To: "U.S. Metric Association" <usma@colostate.edu> > >Pixels are discrete, uniform (within one device) entities. Rather like >ladybugs. I think the proper unit is merely inverse square meters >(m^-2). If one is not averse to using prefixes in the denominator, then >large numerical values can be avoided. > >Sample: >"The display screen of my HP laptop is set to 1680 pixels by 1050 >pixels, for a total of 1 764 000 pixels. Its dimensions are 36.8 cm by >23.0 cm, giving it an area of 846.40 cm2. Its pixel density then is 2084 >cm^-2." > >Note that in the above example, the result could have been given as >20.84 mm^-2 (or 20.84/mm2). If one objects to using prefixes in the >denominator, then this would have been 20 840 000/m2, a rather large and >cumbersome number. Note that I have provided 4 digit precision here, >rather than 3 digit precision, despite the precision of the screen >dimensions. > >Personally, I prefer seeing the number of pixels in a square centimeter >or in a square millimeter. I have no great objection to prefixes in >denominators, especially when there are no units in the numerator. I can >visualize a square centimeter or square millimeter at least as easily as >I can visualize a square meter. But I can visualize 21 or 2100 much more >easily than I can visualize 21 000 000. > >By the way, one must distinguish among native resolution (or pixel >density) and those provided by software techniques. > >Jim > >On 2011-01-14 1059, mech...@illinois.edu wrote: >> Michael, Jon, and Patrick, >> >> The "best" unit for TV screen area (size) is the coherent SI unit "meter >> squared." >> Flat screens of area about 1 m^2 and larger are already quite common. >> >> The "best" unit for TV pixel density is the unit "pixels per meter squared." >> (I hesitate to call "pixels/m^2" an "SI unit." How is "pixel" related to SI? >> >> Of course, SI prefixes may be applied to the numerators of each unit >> (preferably, excluding prefixes in the denominators). >> >> Gene. >> >> ---- Original message ---- >>> Date: Fri, 14 Jan 2011 07:00:14 -0500 >>> From: Jon Saxton<spam.t...@verizon.net> >>> Subject: [USMA:49509] Re: Screen size conundrum >>> To: "U.S. Metric Association"<usma@colostate.edu> >>> >>> I thought about this issue about 4 years ago. I think the best unit for >>> measuring screen sizes is dm² but I expect an adverse reaction from >>> other members of this list. >>> >>> >>> On 2011-01-12 1858, Michael GLASS wrote: >>>> Dear People, >>>> >>>> There's a real problem with electronic screen sizes - all of them. This >>>> includes cameras, video cameras, computers, DVD players GPS monitors and >>>> television sets. >>>> >>>> >>>> 1 Because the screens are different shapes, there is no fixed relationship >>>> between the size of the screen and the measure given. >>>> >>>> 2 Even in cases where there is a fixed ratio between shape of the screen >>>> and >>>> the size of the screen, the increase in the size is not linear, but is >>>> related to the square of the number given. >>>> >>>> 3 As a result, power consumption on larger screen sizes is far higher than >>>> might be anticipated by looking at the screen size. For example, a 15 inch >>>> computer monitor is very nearly a 33% larger than a 13 inch model whereas >>>> 15 >>>> is just over 15% larger than 13. >>>> >>>> 4 With the issue of global warming, the power consumption of larger screens >>>> is a matter of increasing concern. >>>> >>>> 5 Even if you express screen sizes in metric terms the diagonal is still a >>>> misleading measure of the size of the screen. >>>> >>>> It seems to me that the best way to express the size of the screen is to >>>> give its area. So here is my conundrum: would it be better to express this >>>> size in square metres, square millimetres or square metres? What do others >>>> think? >>>> >>>> Michael Glass >>>> >>>> >>> >> >> >> >> > >-- >James R. Frysinger >632 Stony Point Mountain Road >Doyle, TN 38559-3030 > >(C) 931.212.0267 >(H) 931.657.3107 >(F) 931.657.3108 >
