Panels a la carte: Mura, components, dead pixels... - BeHardware
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Written by Vincent Alzieu

Published on September 29, 2005

URL: http://www.behardware.com/art/lire/589/


Page 1

Welcome to the Mura Effect

Introducing the Mura effect
->Consider the following correlation: the price of LCD monitors drops at the same speed as buyers´ interest increases. Starting at $800 for a 19” monitor two years ago (Summer 2003), its price has now fallen to $300 for a brand name monitor and $280 for a generic.



->So taking this into account, what are the factors behind very low priced monitors? How can Fujitsu-Siemens sell a Premium C19-4 MVA 8 ms panel for half the cost of a ViewSonic VP191b equipped with the same panel? Where do the 19” MVAs and 8 ms TNs sold for under $300 come from? What are the real dead pixel risks with these products? And finally, why do some manufacturers have a “zero dead pixel” warranty while others say we are killing them when we suggest following Philips´ example?

We´ve been asking these questions for years now. Sometimes we went straight to manufacturers, but as you may know, sometimes it´s difficult to obtain clear information in such sensitive areas. So we asked the question to a lesser known new manufacturer, Atlantis Land. They are nowhere near giants such as Samsung, LG or the others, but have a “O pixel” product line, meaning “zero dead pixels” whether they are white, black or color. Monitor prices aren’t extreme and the next 19AM-C08 (of the "O pixel" line) will be available in October for 399€. Their representative, Frank Demouth, was very willing to respond to our questions. With these answers we added the confirmation of several manufacturers (which weren’t necessarily eager to see their names in an article entitled “hidden LCD monitor defects”) and new information on today´s topic, the “Mura Effect” and variations in panel component quality. We thank all manufacturers who more or less participated, giving us the possibility to show a defect (another some will say) not covered in the warranty.

The Mura, a defect not covered in the warranty
To begin with, we already know that panels belong to several classes, ISO 13406-2 Class I, II, III and IV, in reference to their tolerance to dead pixels (see this article on the subject). The most common is the second (ISO 13406-2 Class II). We remind you that it considers a 17” or 19” monitor with 2 black or white or even 6 colored dead pixels in the norm. Class one is the strictest with zero dead pixels tolerated. And then there is the III, used by BenQ for the T series. With this norm the number of dead pixels tolerated increases to 5 black, 18 white and 64 colored!

But did you know that there are 6 subcategories within these classes? Panel manufacturers test their products at the end of the production line. They attribute a class AND rank. The best is A+ followed by A, A-, B+, B and B-. Each rank is based on only one criteria, the importance of a defect called the “mura effect”. This term actually refers to several types of problems.


Mura Effect type 1 corresponds to a lack of homogeneity in control circuit adjustments. From one cell to another color control can change and it will lead to permanent defects in intensity in displayed images.

Mura Effect type 2, or Cell Gap Mura comes in two forms. If liquid crystal cell sizes are superior to the normal size in an area of the panel, the images produced in this area will be brighter. This is a White Mura. In the opposite way, if the cell size is too small, it will be darker. This is a Black Mura. Cell distortions sometimes come from a « normal » defect in manufacturing, but most of the times are due to an impurity in the panel such as dust, a drop of some chemical or an accidental ionisation of liquid crystals, which then misalign. For the first two cases, it is possible to move the defect by gently pressing the panel with your fingers to move the Mura to the side from a useful area in the screen. In the case of ionisation, the defect can fade or even disappear with time. For us it was the opposite with the appearance of a Mura on two monitors after a few years of use (three and five years, respectively). It looks as if you were pushing on the screen with your fingers except now it´s permanent.

Mura Effect type 3 is related to distance or defects between the panel and liquid crystals. This occurs when the panel is sealed and side pressure is imperfect. If it´s too strong, cells are crushed and there is a bright halo in a corner along the panel.

These are the three types of Mura effects detected in the factory. Two others exist:
  • One Murat effect can appear when color filters (red, green and blue) placed on cells are made of different materials, which react differently to heat and light,
  • the next one can be included as a manufacturing Mura, even if it isn’t one. The “spot” is a mark on the backlighting itself. It doesn’t properly light up an area of the monitor and causes a small spot of 1 to 5 mm in diameter.

    Panel and processor manufacturing are similar. The best possible panel is produced and there is a sorting at the end of the production line resulting in a full classing. A product line´s can vary in price from 5 to 7% from class to class. The gap between an A+ and B- panel can be up to 30% within the same line.

    For example, a 19” MVA 25ms panel will be sold $200 if it´s a B- and $260 if it´s an A+.


  • Page 2
    Quality falls again : panels a la carte

    Quality falls again : panels a la carte
    Monitor manufacturer then have the possibility of customizing their panels. They have several basic electronic component sets (sometimes customizable) and several qualities of backlighting. For example, fluorescent tube life (MTBF, Mean Time Before Failure) varies from 25,000 to 50,000 hours. It is up to consumers to see what the monitor is equipped with as this data is theoretically available in the monitor specifications. Pixel command components and backlighting quality, however, is never disclosed. In fact, the MTBF for backlighting control is always shorter than for the tubes. How much shorter? Nobody could give us a straight answer for this question. Once again, it varies according to manufacturer spending. This is the same for the power adapter whether it´s internal or external. The difference in cost between low and high quality components (except for customisations as NEC and Eizo do with brightness sensors, etc.) is around 10%


    Once the panel, class and rank are chosen, the only question left for manufacturers is whether they want monitors with or without dead pixels. Half of Atlantis Land products have the « O pixel » warranty. To maintain this warranty, they buy a specific “sorted Class II” and ranked A+. (Different from a Class I which guarantees zero dead pixels, this warranty only lasts one year for Atlantis Land and then changes to a standard Class II type). As the sorting isn’t quite enough, their Asian offices check each batch during assembly for product quality. Additional cost for this zero dead pixel operation? 10% of the panel price answers Atlantis Land.

    To have a “Zero dead pixel” monitor by sorting out panels results in a 10% price increase. For a monitor sold initially at $500, it goes up to $550. This isn’t surprising as this difference is the price of a zero dead pixel warranty sold by a growing number of stores.

    Manufacturers could also directly choose Class I. According to another source, this operation would not be very profitable and would cause a 20% additional cost compared to a Class II. On the other hand buying Class III would reduce costs by 10-20 %.

    In the end, the panel and components represent 80% of the monitor´s price.


    Page 3
    Exercise : building a cheap monitor

    An exercise for everyone : building a cheap monitor
    Lets now see how to build a basic monitor and how much it will cost.

    Prices indicated below aren’t accurate. Neither Atlantis Land nor any other manufacturer gave us these figures, these are just estimations.

    Let´s take the typical case of a $400 monitor. We can imagine that it´s a Class II A+. First, let’s remove the 10% shop margin : the monitor is in fact sold at $360. $360 = fabrication cost + transport. Out of the 360€, 80% is the panel price or $288 for a Class II rank A+.


    We can realistically assume that a manufacturer wanting to produce an inexpensive LCD will buy the same panel but with a lower rank than A+ for approximately $223. They can then save some money on components, say 10%, reducing the figure to $201. The last price cut can be in Class, which can make quite a difference. Going to Class III can mean a further 10% or $181 per panel.

    With the same panel and identical specifications including backlighting MTBF, the price gap is 35% (difference between the initial $288 and $190 price).

    This Class III B ranked monitor price with the same panel as the reference monitor could be $228, if you add 20% for the body, transport, etc.

    If you take a look at prices currently in stores, our exercise is roughly based on reality as this is the price of some TFT monitors currently available.


    Page 4
    Conclusion

    Conclusion
    Dead pixel warranties aren’t great, but at least they related to the ISO norm13406-2. Components, power supplies and backlighting are also covered by warranties. If a manufacturer chooses the economical path, it will result in more or less satisfying results (see the noted quality differences between the ViewSonic VP191b and Fujitsu-Siemens C19-4), and in case of failure you will be covered.

    Nothing protects you from the Mura Effect, however, or very average display quality because of poor quality components. It´s all the more unpleasant to learn that manufacturers know this before selling some of their products, like we have seen with Dell (bright halo) or Apple (dominance in pink). Those who simply produce panels and don´t resell them seem to be more straight forward. They sell panels with defects and it isn’t really their fault if some companies big or small, do things to reduce costs. One manufacturer who contributed to this article told us that we have to be realistic, 20 to 30 % of panels produced are defective…but nothing ends up to the trash.

    The only way to protect you is to look at consumer protection laws and store policies. Like we said before in the dead pixel article, some stores have money back guarantees and you shouldn´t have to justify yourself for any reason in returning the monitor. For example, the presence of Mura effects.

    Our last point is very important and concerns another risk. It´s quite common when a new brand shows up in stores and then disappears. Check who handles the warranty. The brand (serious or not?) or is it the store? If you buy a sub-sub brand monitor don’t do it from a small retail shop that maybe won’t do anything for you later.

    To finish this article we are gong to sing (or to be accurate yell) our favourite same old story:

    Part 1:
    When will they finally revise the ISO 13406-2 norm?
    We are fed up with fake claims,
    Why do they tell us useless things?
    When will they finally use a representative response time measurement?
    When will there be a valid viewing angle measurement?
    From now on the panel ranks should be indicated
    Indicated MTBF must be the shorter whether it´s backlighting or component
    Ideally all components should be indicated in the product characteristics

    Part 2 :
    Of course we have to be realistic
    This info we will always to find ourselves
    We´ll do our best in the next survey.


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