I live, eat and breath LCD screens in my current job, and just returned from the CES show in Las Vegas, where there were, literally, tens of thousands of LCD screens in sizes ranging from 15 mm to several meters diagonal. (3D was the hot thing this year, but that's another topic.)
The unfortunate thing is that LCD vendors, which are almost exclusively non-USA, still measure screens in diagonal inches. I do not believe I saw a single screen specified in metric units. I have some literature that is entirely in Chinese, except a few technical specs, and right there is "7" 800x400". In fact, almost exclusively screens are specified as "N" diag, X x Y pixels." Since (as far as I know) all pixels are square these days (they didn't used to be), that really fully entirely specifies the screen (with appropriate calculations): aspect ratio, width, height, pixel density, area, etc. My own company specifies screen sizes in "mm (in)" (see QSI Corporation ) but we are really a loan wolf in this regard. In fact, we were recently purchased by a Swedish company, and they use only inches! (see Beijer Electronics ) What I am saying is this: none of us like the current method of specifying an LCD screen (N" X x Y pixels), but it is so deeply ingrained in a huge, world-wide market, that I do not see it changing for a long, long time. Finally, some comments in this thread suggest pixels per centimeters. Most technical work I have been involved in eschews centimeters, and pixels per millimeter would be preferred. Jim ----- Original Message ----- I don’t think anyone is asking this forum how to evaluate screens. 1. The wiki for pixel density <http://en.wikipedia.org/wiki/Pixel_density> does give pixels per (linear) centimeter, which I hope is standard (instead of pixels per inch) in most of the world. Is that OK with everyone? 2. Also, should screen area be given in square meter, or some other unit? These are two questions that I hope this forum will weigh in on, for my own reference. Energy and aspect ratio look like digressions. = = = = On 1/13/11 11:23 AM, "John M. Steele" <[email protected]> wrote: My view is that there is not a single spec that tells us everything we need to know about a display. My personal opinion is that some linear dimension gives me a better feel for the size of display than an area. I would prefer height and width (like a piece of paper) but I can live with diagonal and aspect rate. TV and computer screens are almost always the classic 4:3 and high definition 16:9 aspect ratio. Additionally, you need to know something about resolution (pixels), color fidelity, contrast ratio, maximum screen brightness, and power requirements. Different technologies require different power at different screen sizes, so just knowing area doesn't exactly predict power requirement. ________________________________ From: Patrick Moore <[email protected]> To: U.S. Metric Association <[email protected]> Sent: Thu, January 13, 2011 10:58:07 AM Subject: [USMA:49493] Re: Screen size conundrum I am waiting to see how people will answer Glass' question, which is really about unit selection (square millimeters vs. square meters), not energy vs. power. The issue is relevant also for expressions of pixel density, or screen resolution: WOMBAT pixels per inch or SI pixels per. . . millimeter or centimeter or meter? Screen resolution or pixel density is measured along a horizontal line and seems to be expressed most often in pixels per inch or pixels per centimeter. Is this a case where centimeters work better than millimeters? = = = = On 1/12/11 6:58 PM, "Michael GLASS" <[email protected]> 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 > -- ********************** Jim Elwell [email protected] 801-466-8770 www.qsicorp.com
