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
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Doyle, TN 38559-3030
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