Re: Digital TV suppliers urged to save energy

The message <Xns977E27E419AB3JavaJive@xxxxxxxxxxxxxxx>
from Java Jive <java@xxxxxxxx> contains these words:

Johnny B Good <jcs.computers***@xxxxxxxxxxxxxxxx> wrote in
news:2006030401471285168@xxxxxxxxxxxxxxxx:

For the home user, who (usually, if they have any sense) has the
luxury
of picking a properly sized desk for the job, it doesn't make too much
sense to invest in an overpriced fragile and totally immature display
technology which is almost certain to be overtaken by alternatives,
such as OLED based (or whatever turns out to be the right way to go
:-).

Ah! I sense another irrational peddling of folklore from the computing
dark ages ...

Whilst standalone flat panel displays have undoubtedly improved on
the
older notebook displays, they still have many shortcomings as a
display device compared to CRT displays.

Yep, thought so - rubbish!

1) The most important reason for buying an LCD monitor is your health.

All CRTs produce low intensity X-rays as an inevitable consequence of the
physics underlying their technology, and as X-radiation is carcinogenic,
and seems to cause eye-strain, all CRTs are something of a health hazard.

In America, the early colour TV set designs did produce copious amounts
of X-Rays, not from the picture valve (tube) but from the thermionic
vacuum tube EHT rectifiers being used. Since the bulk of the picture
tube shaded the viewer from the eht rectifier, the risk was considerably
reduced and most of the X-Rays tended to be beamed downwards (People on
the floor below were at greater risk!). You'd have to be in the habit of
lying underneath the TV set for several hours per day before the risk
factor became meaningful.

Colour CRTs produce more radiation than monochrome ones (3 electron guns,
or a bigger one split into three beams), and the higher the brightness
control, the greater the level of radiation given off. Concerns about the
long-term effects of CRT X-radiation led to successively more stringent
standards for monitors:
MRP-2, TOC-92, TOC-95.

Monochrome monitors simply didn't use high enough EHT to produce X-Rays
(about 12 to 14Kv, ISTR). The risk was only present in the colour sets
requiring EHT voltage around the 24 to 26KV mark. Once the use of solid
state rectifier diode strings became common practice, the main source of
X-Ray radiation disappeared, leaving only the lower level source of the
shadow mask nicely tucked away behind an inch of glass.

Glass by itself is almost opaque to X-Rays but the practice of adding
lead to the front glass of the tube to improve the shielding effect has
been common over the last 15 or so years. The X-Ray risk has been rather
overstated to say the least.

The real problem is down to eyestrain caused by perusing close up
detail for far longer than is good for you and the less obvious flicker
induced fatigue due to an insufficiently high enough vertical refresh
rate being selected by default.

People have actually been concerned about this from the advent of TV - if
I walk into a family home and see the children sitting on the floor too
close to a big CRT TV, I always advise them to sit further back - but it
only really became a big issue with the advent of computer monitors,
because:

a) People sit relatively closer to monitors than TVs, and distance from
the source is an important factor in the level of risk. The radiation
received by a point target, such as a human body cell, from a point source,
such as a phosphor dot, falls off by an inverse-square law (each doubling

So we're talking about visible radiation in three narrow(ish) colour
bands (RGB)? The phosphors aren't the source of the low level X-Ray
hazard, it's the well shielded (by the one inch or thicker lead loaded
glass) shadow mask (or it's equivilent)

of the distance between them quarters the radiation received); the maths
for an array of point sources such as a monitor being received by the whole
of your body would be somewhat more complex, but you get the idea.

No, the math is quite simple. If you calculate a certain amount of
radiation from a point source, that from a hundred such point sources
confined to an area at right angles to the axis of propogation that
subtends an angle of just a few degrees will very closely approximate to
100 times that of the single point source.

One of the side effects of the bulk of CRTs is often that on a shallow
workspace their depth places the screen even closer to the user, and in the
past this has happened to me with bad results (see below).

That's just bad practice. I have a standard office desk with a depth of
30 inches and my 19 inch monitor screen is a good 2 feet away from my
face whilst I type.

The mistake often made, regarding desk layout in a domestic setting, is
placing such desks too close to a wall thus preventing the monitor from
being placed as far back as it's base will permit. My own desk clears
the wall by 9 inches leaving 1 inch between the back of the monitor and
the wall.

b) While TVs are used at the standard frame rate of 50 or 60Hz, monitors
are usually used at higher refresh rates, and give off proportionately more
radiation.

Wrong, refresh rate makes no difference to what little radiation risk
that might possibly be present. Low refresh rate is worse since it
fatigues the visual cortex by exciting the peripheral vision evolved to
detect changes rather than detail.

High enough refresh rates (75Hz up to 100Hz non-interlaced)
considerably reduce this fatiguing effect. Only the really cheap designs
fail to manage at least 75Hz at the desired resolution and most
reasonable 17 inch and larger models will happily display the
recommended resolution at 85Hz or higher.

c) People working at a computer spend much more time in front of a monitor
than an an average viewer spends in front of the TV.

The real problem is in the fact that computer operators sit a lot
closer to a monitor than they would a TV set. A computer monitor
occupies a much larger viewing angle than does a TV so far less
opportunity for the eyes to de-accommodate as they inevitably scan the
scene before them. That's why, istr, a recommendation to take short
breaks every 15 to 30 minutes.

Cancer aside, the radiation from CRT monitors almost certainly causes eye-
strain in the short term and risks damage to your eyes in the long term.

Wrong, the only radiation involved in the 'eyestrain problem' is that
which resides in the visible spectrum. If X-Rays were present, they
certainly _ wouldn't_ be causing eyestrain.

With a CRT I found I used to have to stop work to rest my eyes at least
every one or two hours, but since acquiring an LCD, I can basically work
indefinitely, the only things I have to stop for are the normal bodily
functions.

Most likely you are benefiting from the elimination of 'refresh
flicker' and a slight reduction in total front panel surface area to
obscure your view of the more distant parts of your environment. (LCDs
usually have a smaller bezel area than equivilent sized CRT monitors)

Further, for a year or two at work I lost control of my workspace, and was
forced to sit closer to my CRT monitor than I wanted to, and at the end of
this period I found I needed glasses. Since acquiring an LCD, my eyesight
has not noticeably deteriorated further.

You're just noticing the age induced deterioration of visual
accommodation for close objects which, sadly, everyone succumbs to
(usually around their mid fifties).

While my experiences on their own are anecdotal, last time I searched the
web I found enough similar personal stories to be convinced that CRTs are
not good for your eyesight.

Undoubtedly, in the main, due to slow refesh rates.

2) After a while, CRTs go out of adjustment and the picture gets slightly
out of focus and fuzzy. This would probably go unnoticed on many TVs but
is particularly disastrous for a computer monitor, because of the
requirement to be able to read text on them. Unfortunately, the natural
counter for this is lean forward to read the small print areas, and we're
back to distance again.

Leaning forward to compensate for a lack of focus in a CRT won't
compensate. If you're actually benefiting by closing the viewing
distance, the problem _isn't_ a lack of focus by the monitor (in this
case the problem is with the operator).

3) Even the flattest squarest tubes I've ever seen had some geometric
distortion, while LCDs have none.

The minor geometric distortions are a small (and very acceptable) price
to pay for better colour rendition and viewing angles and freedom of
choice in optimum screen resolutions to match the apps being run.

4) CRTs often have poor hue (colour balance), just compare the colours in
a line of TVs in a shop, or monitors showing the same corporate screensaver
in a workplace, and you'll frequently see widely differing results. There
seems to be more uniformity in hue between LCDs.

The overall hue might be more uniformly adrift in an LCD than in a CRT,
but this just reflects the wider range of adjustment available in a CRT
based display which might well have three pre-defined colour temperature
settings to choose from.

5) While early LCDs had a rather poor viewing angle, modern ones are very
good. I have no complaints about either my monitor or my TVs in this
respect.

6) So the only thing that's left is that CRTs have a slightly better
contrast ratio, but it's so slight that I don't notice it in practice.

I'm not surprised.

Hence I would unreservedly advise anyone to buy an LCD monitor.

And I wouldn't, meaning I would only recommend an LCD _with_ reservations.

While a TV is more about making your choice based on your budget, etc, I
still think that overall they are very good buy now that their prices are
dropping significantly.

They may well be better value than they were a year (or even six
months) ago, but that still doesn't make them the best choice for the
job.

Even assuming an average of 12 hours use every day, the home user is
only going to save a mere 20 quid a year on the electricity bill for a
45 watt reduction. I, for one, will not be rushing out to replace my
19 inch crt monitor just for 'change sake'. If the monitor expires out
of warranty, I might _then_ consider a flat panel if they've improved
enough by then _and_ dropped in price. :-)

And this reasoning is as true in wider environmental terms as you've hinted
at in financial terms, because just as the user has to maximise the
'return' in use on his/her financial 'investment' in the cost of an item,
so ideally (s)he should maximise the 'return' in use on the 'investment' of
environmental damage caused in making it.

This is highlighted by low-energy lightbulbs. Does one throw away a
perfectly good working lightbulb and replace it with a low energy one, thus
wasting the energy already expended in making the original? People seem to
be being advised to do this, but I'm not convinced it's best
environmentally. Personally, I use old bulbs until they pop, and then
replace them with low energy ones.

Actually, in this instance, you'd be doing the environment a big favour
by evicting those tungsten GLS lamps from your light sockets as soon as
you can get hold of their CFL replacements.

HTH

--
Regards, John.

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