Community Newsletter: Q&A: 12/16/05

errata

In reply to: 12/16/05 by Lee Koo (ADMIN) 

Although fairly accurate in the some areas, in terms of the question actually asked, this answer was filled with inaccuracies. To wit:

''There are essentially many benefits of LCD beginning with, what in my eyes is most important - ELF \VLf, which goes under electromagnetic radiation emissions in CRT caused from the scanning beam. LCD does away with this.''

First, the electron guns are NOT the cause of EMF or VLF in CRTs. These are caused mainly by the vertical and horizontal deflection yokes, respectively, as well as the power cord and the high voltage transformer. Second, there is absolutely NO empirical evidence that the particular EMF frequencies emitted by CRTs causes ANY affects on macroscopic biological systems. All we have is conjecture based on single-celled organisms, and EMF pulses delivered to lab animals by Tesla coils at powers and frequencies NOT emitted by CRTs.

''This was also the reason for many glare screens on CRT monitors.''

No, the cause of this was the necessary curvature of the CRT tube itself. Modern flat screen CRTs have little to no glare, just like LCDs.

''There is a counterpart to this - the flicker you get from the refresh rate on CRT which causes symptoms such as eye strain, headaches, motion sickness and is called computer vision syndrome.''

Again, no. First the comment that flicker is caused by refresh rate is, by itself, meaningless. How does a rate cause flicker? Flicker is caused by the low refresh rates of older low resolution monitors. Modern CRTs have almost no flicker, due to substantially increased refresh rates at the higher resolutions. I could not even parse most of the rest of the accompanying paragraph, except:

''As far as GLARE is concerned, it is fairly done away with as LCD uses a plastic film instead of glass to reduce glare.''

Most modern quality non-laptop mounted LCD screens use glass, not plastic.

''However, LCD is far more adjustable on the pivot arm than CRT and many times can make up for the lack of angle viewing.''

Personally, if it weren't for the cables, my CRT would rotate 360º. Beat that with an LCD (without cheating and rotating the stand, of course!)

''Straight on viewing in LCD is geometrically better since it lacks the distortion of CRT and your screen view is focused, you see your whole screen, and portions are not lost or out of proportion. This is the reason a 15 '' LCD may give you close to a 17'' CRT display.''

Where to begin. First, quality flat screen CRTs, the ones being enquired about here, do not suffer from significant distortion. Portions are not ''lost or out of proportion'' on CRTs, they are masked. Also, this distortion is not really why 15'' CRTs are equivalent to 17'' CRTs. The images are masked to cover the area where the beam must reverse direction. This DOES cause distortion, due to EM effects related to monitor size and the curvature of the earth, but this effect does not affect the image substantially on a good CRT.

''Refresh rates in LCD have surpassed or equaled CRT. There were many issues with GHOSTING on the screen, which when playing a movie, or high end video game, left an image behind itself when movement occurred. Many LCD companies have solved this issue also. ''

Not really.

''One drawback of most LCDs - the native resolution is a set resolution and can be changed, but you may get quality loss and performance loss. This is also being worked on and will not be an issue in the near future. Some still say that LCD cannot surpass the color depth of the CRT, but that is changing also. In general, an LCD will be up to any lacking that a CRT can provide. For a typical user, the color depth will not be an issue as it comes into play with graphic artists and such.''

Again, no. The native resolution of LCDs can not be changed, only its interpolated resolution. That is why the image is often very sub par. People say an LCD cannot surpass the color depth of the CRT for a simple reason. Because they can not. That is why almost no digital graphics professionals, especially those who work for print media, use LCDs.

''EMI (electro magnetic interference is still an issue with CRT. For example, speakers too close to the monitor will cause distortion, green or white patches, among others. LCD is not affected by EMI (in most) and has protected circuits, so it is covered from EMI. Some very cheap brands do not use protection, or use low protection, on their circuits, but this is rare. While extremely high EMI's may still affect an LCD, in most cases it is no longer a concern.''

Nor is it a concern for most new, quality CRTs.

''CRTs were known for having a sharper, true color image, but with active matrix display, the LCD refresh rate is higher than on most CRTs. The technology has a price currently, but active matrix, in my opinion, will become a standard and the price will narrow.''

This particular comment evidences what appears to be the fundamental flaw of this response, that it is based on data that is years, if not decades out of date. Active matrix displays surpassed passive matrix systems as the market standard ages ago. In fact, one would be hard pressed to find ANY passive matrix displays on the market. But just as LCD technology advanced, so too did that of CRTs.
Also, colour fidelity has nothing to do with refresh rate, but rather the underlying technology for colour generation. Again, all but every graphics professional uses CRTs.

The part about backlighting is nonsensical, so I can not comment, however:

''LCD's also generate very little heat as opposed to CRT monitors, and this has much to do with less circuit breakdown and longer overall life of the monitor.''

Not really true if you include the power brick, which can throw off enough heat to heat a small room. This is only fair, since it is the enclosed power transformer in the CRTs that is causing THEM to heat up so much.

In closing, the decision to buy LCD or CRT is not as clear cut as the writer states. If size, weight, power consumption, or features are important LCDs may be the way to go. If colour fidelity, cost, or viewing angle win out, so, too does the flat screen CRT.