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Monitor Basics - LCD vs. CRT
Herbal V wrote in with a little article discussing the differences between LCD and CRT. Briefly summarizes all the major issues (Price, Refresh Rate etc). More of a beginner level piece, but as LCD prices are dropping like rocks, it's good to be aware.
Monitors - LCD vs. CRT
As the technology has improved and the prices have come down, LCD (Liquid Crystal Display) monitors have rapidly been replacing CRT (Cathode Ray Tube) monitors on desktops around the world. ComputerWorld first reported that LCD sales would surpass CRT sales for the first time in 2003, a lead that it didn't hold for good. But according to DisplaySearch, a flat panel display market research and consulting company, the sales of LCD monitors regained the lead over CRT sales in the third quarter of 2004,a lead that it should eventually hold for good.
The question is why choose LCD over CRT? There are several pros and cons to consider, and a few items will be considered in this Tech Tip, such as: Price, Size, Image Quality, Energy Consumption, Personal Comfort, and Response Time.
Price
The price of LCD monitors is much lower than a few years (or even months) ago, but still far exceeds the price of a comparable CRT monitor. For example, I spent about $600 (US) on a Viewsonic VA-720 17" LCD monitor in early 2003, and see that the same model now sells for less than $300. A significant price drop, but in comparison a 17" Viewsonic CRT monitor can currently be purchased for less than $100. The ratio of prices may have narrowed from about 5:1 to 3:1, but the aging technology behind CRTs still allows it to hold the lead.
You can't even compare prices of CRTs to LCDs in ComputerGeeks.com's monitor section as they are right in step with the sales information provided above, and now only carry LCD monitors. Prices vary, even among LCD monitors of the same screen size, so there has to be something more to it than price.
Size
One reason that LCDs have gained in popularity is because of their small foot print. The overall size and weight of CRT monitors far exceeds that of LCD monitors. CRTs share the same image processing technology with tube televisions, and therefore share the same bulky style of housing. For example, the manufacturer's web page lists this ACER 19" LCD monitor as having a depth of a mere 6.9" (including the base) and a weight of 12.1 pounds. As a point of reference, a 19" ACER CRT is significantly larger with a depth of 16.86" and a hefty weight of 46.31 pounds.
Desktop real estate is precious, and an LCD will require only a small fraction of the depth that a CRT would require. And if there isn't even enough room on your desk for a slim LCD monitor, the low weight makes them perfectly adaptable to be hung on the wall, or off of a radial arm mount, such as this one from Office Innovations.
Image Quality
Image quality is generally considered to be better on an LCD, as each pixel is generated by a specific set of transistors in the screen, which produces a crisp image. But some features that fall under the general heading of image quality might not favor an LCD, including viewing angle, brightness, and contrast.
Early LCD monitors had a fairly narrow viewing angle that made clearly seeing the screen from anywhere but directly in front of it difficult. This has improved greatly, but still doesn't quite rival the viewing angle of CRTs which provide the same picture quality regardless of the angle. A monitor with a maximum vertical viewing angle of 120 degrees should not be hard to find at this point, with many monitors now being able to provide an even greater angle.
Brightness is an area that LCD monitors may have the edge over CRTs, but it varies widely from unit to unit. The standard measure for brightness is referred to as "nits", which have units of cd/m2 (candelas per square meter), where a higher number is better. Looking at three of the 17" LCD monitors currently available from ComputerGeeks.com as examples shows two with brightness specifications of 400 cd/m2 and one with a brightness specification of 250 cd/m2. As a comparison, the typical CRT monitor may provide half the brightness of an LCD, as confirmed at Viewsonic's Monitor University.
Contrast is similar to brightness in the fact that
I just recently purchased my first Mac. Scary I know but I promise not to become a Slashmacbot... Anyway, in line with the purchase I figured why not move to an LCD setup as well? This article explains several of my reasons for doing so but leaves one out...
Energy Consumption
LCD monitors definitely hold the edge over CRT monitors when it comes to being energy efficient. The huge tube in a CRT monitor is the source of most of its energy consumption, and a comparably sized LCD may use just a fraction of the electricity. Taking a look at this 19" Jetway LCD monitor shows that it consumes 48 Watts during normal operation, which is less than your typical light bulb. In contrast, a 19" CRT such as this one from Viewsonic may draw up to 160 Watts. Therefore the fraction of electricity used in this case is 3/10, and could translate to noticeable savings on your electric bill.
I currently have two 17" CRT monitors on my L-shaped desk. One is a newer model "flat screen" and the other was a freebie HP branded CRT. I know that they are sucking power and sending that power back out as radiation directly into the side and front of my face (as they are surrounding two of the three sides of my head). I have switched to a lot of energy saving bulbs in my house and I plan to switch more as the bulbs die off. I have switched to a programmable thermostat (that isn't 5 degrees off like the one that the original owners had) to save electricity/gas during the day and evenings. Why not my computer crap too?
I have even gone so far as to make sure that if I am not going to be home for more than 24 hours my non-essential computer equipment is off. A few bucks here and there equals beer later.
Personal Health and Comfort
The main benefit that LCDs have when it comes to comfort is the reduced strain on your eyes. The reduced glare on the screen's surface, and the elimination of a typical CRT's "refresh", can prevent your eyes from getting tired from extended use. A CRT monitor redraws the image on the entire screen as it refreshes, whereas an LCD monitor only changes the necessary pixels during a refresh.
There may also be the unquantifiable effect of reduced electromagnetic emissions on LCD monitors. The exact impact of electromagnetic emissions may not be fully understood, but in general less is considered to better, as addressed in this article. And, your back may also appreciate an LCD when it comes time to move, as the example above shows a 19" LCD monitor weighs about ¼ as much as its CRT counterpart.
What I have noticed is that using both at work (and now both at home) that I have significantly MORE eyestrain. Moving back and forth between the two seems more harmful than just sticking with one or the other. Sadly I am going to be in this situation at home for a while yet but at work I have only this 20" CRT to replace. The 23" LCD is in IT and waiting for install so it won't be too long. I was QUITE surprised when I went to pick up the 17" LCD at the FedEx hub that it fit easily in my trunk and was light enough for me to hold with one arm safely. I can't say that much about lugging my 17" CRTs around. Woo for that.
My other reason for loving LCDs is desk real estate. With my CRTs tons of desk space is lost to their screen, their rear ends, and their bases. With the new LCDs I have quite a bit more room to stack cans, plates, etc. It also makes me feel more "free" to move around in the tight space that my computer area is located.
I look forward to my second LCD at home and the savings in health, energy, and space it will give me.
It depends...if you're using the VGA input, the card is still outputting an analog signal with refresh. It's handled within the monitor with an analog to digital converter. So as long as you don't specify frequencies or refresh rates that the converter can't handle, there's no problem. I usually just set mine to 75 Hz. If you're using DVI, then none of that applies...but monitors that support DVI are still too expensive.
Try this article for a good overview of the different types of LCD panels (TN, MVA, PVA & IPS):
X-bit's Guide: Contemporary LCD Monitor Parameters and Characteristics
It weighs in at 27 pages, but if you really want to know what you're talking about when discussing LCDs, it's required reading.
Site & blog: http://www.mayaposch.com
Here's some of my experiences buying an LCD monitor. If you're not picky, it's easy to buy one; if you're picky, well, it's not so easy.
The manufacturers don't give enough specifications to evaluate the response time properly. The response times refer to a fully-off to fully-on step transition, which is actually the fastest response a CRT has. A change from 50% gray to 51% gray will be very slow, by comparison, and that's much more important for video. Some LCD displays have circuits that intentionally overdrive the pixel to get faster small-signal response, but it is difficult to find out which manufacturers to this. The best way is to hook up a video source and just watch it.
Most monitors I've seen specifically request ONLY 60Hz for their analog connections. If you set it at anything higher, you will get some sort of "Out of range" message on all but the best (Viewsonic will allow higher refresh rates on a temporary basis, but constantly nag you to lower your rate to 60Hz).
Homer no function beer well without.
It doesn't hurt to be nice.
This is known in general as "sub-pixel rendering". It's available in Linux and on Macs. Check a control panel / system settings / control center module near you!
Use the Firehose to mod down Second Life stories!
Also be sure to download the ClearType Tuner Powertoy. There's a web version, too, but it doesn't seem to work with Firefox.
"The article only briefly mentions response time -- doesn't explain it."
TomsHardware (don't pretend you need a link) have been plotting response-time against brightness change in their reviews recently, showing the advertised 14ms (or whatever) on the black-white transition, and response times increasing for changes of greyscale (with a peak somewhere around the 25% brightness change of maybe 30ms for a "14ms" monitor)
Comments on aria also mention that images seem to linger longer when there is blue involved, perhaps giving another insight into the fudging of numbers which is used to calculate the published response speed.
Actually, CRTs are also made of separate coloured elements. I don't think ClearType can be used though because it's very hard (impossible?) to address individual screen elements accurately with a CRT.
You need the ClearType Tuner PowerToy ClearType Tuner (New) This PowerToy lets you use ClearType technology to make it easier to read text on your screen, and installs in the Control Panel for easy access. Cleartype Tuner PowerToy
Don't give up, give a quality LCD a try first and you may never go back.
Response time is a critical feature for me. I won't buy any LCD screen unless it's in the 16ms-or-better range for typical pixel response.
My NEC LCD1760NX is great for games and movies. No hint of ghosting at all. Solid, bright, good footprint too. Digital/Analog connections as well.
LCDs still have problems with color correction for serious graphics work, or so I'm told. But you couldn't pay me to get in front of a CRT anymore. My eyes won't take it.
Here's a great overview of what cleartype is and does and how it works. Also, in OS X, go to System Preferences, Appearance. If you choose "medium - best for flat panel" that will activate sub-pixel rendering.
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A response time of 40ms means it takes a pixel 40 milliseconds to change color. At that rate, it can change 1/.040 times per second, or 25 frames/sec if new images are perfectly in sync (and they never are). That's slow enough that most people will notice rapidly changing images bleed into one another as the pixel is given a new value more rapidly than it can change. Thus a 40ms LCD is a poor choice for action games and DVDs. It may be fine for web browsing, word processing, and email.
Newer LCDs typically have 25ms (40 fps), 16ms (62 fps) or even faster response times. Look for them if that's important to you.
The difference between CRT and LCD is the arrangement of the pixel elements.
b rgbrgb
In a CRT monitor, an individual pixel is made up as a triangle with RGB on each corner.
However, on an LCD, the individual color elements are arranged in horizontal strips
rgbrgbrgbrgb
rgbrgbrgbrgb
rgbrgbrgbrgb
rgbrg
rgbrgbrgbrgb
On a CRT monitor, a dot is basically a dot.
On an LCD, its a strip.
Cleartype works by performing antialiasing on these elements, but "borrowing" adjacent color elements.
liqbase
Is it true that DVI is limited to 60hz, and so that even if LCD refresh times improve, DVI always will be limited?
LCD refresh rates won't "improve", so you can stop worrying about that.
The reason that they won't improve is that 60Hz refresh is plenty enough for an LCD monitor, even with fast motion video on it. The CRTs need a faster refresh rate because they flicker, i.e. each pixel's brightness gradually falls off from refresh to refresh. LCDs don't flicker, i.e. a pixel stays at the same exact brightness the whole time between refreshes, so the refresh rate is limited by the desired frame rate, not flicker, and you really don't need faster frame rate than 60Hz.
I've been in charge of buying flat panels for my company for the last few years. In that time, 20" LCDs from Dell have gone from $2000 to $599. In the same time, high-end Apple LCDs have gone from 22" 1600x1024 for $4000 to 30" 2560x1600 for $3000 (plus a $600 video card to run it.) If you haven't seen any drops, you haven't been looking very hard. As for your last point, I can go to CompUSA and buy a 17" LCD for $279 or a 15" laptop for $649.
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> Most good CRT's go up to 2048x1536
Name one. I have a recent NEC 21" Diamondtron. Sure, it'll sync up to whatever the video card can churn out, but I'm quite confident there's only about 1600 physical 'dots' from left to right.
The font I use has little m's and w's that are basically alternating vertical lines, on-off-on-off-on. It took careful tweaking just to get them distinguished at 1600 and it was clearly not possible at 1900. Look realy really close. I even had to force the vertical refresh down to 60Hz just to keep the signal from blurring too much.
The article overlooks one of the biggest reasons to not buy an LCD monitor: The bad pixel problem.
Whether it shows up as a dark/missing pixel on brighter images, or a bright pixel on dark images, this persistent problem is an ugly side of LCD monitors.
Ever since buying an iMac with a single bright blue pixel on its LCD, I've resolved to never again buy another LCD that isn't warranted to be 100% defect-free. At least for now, no manufacturer except for Samsung (and only in S. Korea) seems to believe that more than zero bad pixels constitutes a problem.
The general line still is that a bad pixel or two is "normal". Well, it is as normal as an LP album with a scratch, a CD with an intermittent skip, or a dropped cell phone call. It happens, and much of the buying public accepts it, but it sucks and such garbage has no place in a quality product.
Vote with your pocketbook. I do. Caveat LCD emptor!
Actually, I do need a faster frame rate than that. I work with applications that require images to appear on screen for a few milliseconds, and 60hz doesn't cut it for that.
As a result, this kind of anti-aliasing just isn't possible with a CRT. You can't really know, programatically, when each colour dots are going to be illuminated.
By comparison, LCDs have a 1:1 pixel colour component to screen pixel colour element mapping (assuming you're running it in full resolution of course, but if you have a 640x480 view stretched to fit a 1024x768 LCD screen then it's going to look pretty ugly regardless...), hence this trick works.
You are not alone. This is not normal. None of this is normal.
This was a beginner's article, but the author probably should have mentioned these other caveats with LCDs:
Native resolution issue mentioned above.
Dead pixels. Unless you have several, mail-order companies won't issue an RMA. I bought a model that was reviewed on newegg.com by umpteen people and many said they had no dead pixels. Naturally, mine does. Fortunately, it's only one.
Gamingmuseum.com: Give your 3D accelerator a rest.
What exactly are people supposed to be aware of? That you got sick while using multiple CRTs? That people in general get sick from over exposure to CRTs? That the risk of illness is large?
Testimonials do not drive good medical science.