What is an acceptable level of dead pixels?

What is an acceptable level of dead pixels?
 
Previously, we have already known that dead pixel is inevitable to some extent due to the highly complicated manufacturing process.
To regulate the acceptability of defects and to protect the end consumers, International Standard Organization (ISO) has created a standard for manufacturers to follow. ISO-13406-2 recommends how many pixel faults are acceptable before a panel can be replaced.
 
ISO defines 4 levels of quality for LCD panels. According to ISO13406-2 norm, LCD can have following type of defective pixels:
Type 1: number of always-lit pixels, also called white pixel or colored pixel (it appears randomly white /red/green/blue.).
Type 2: number of always-unlit pixels, also called black pixel or missing pixel (it appears as a black dot on light-colored background.).
Type 3: other defects, particularly on sub-pixels and the RGB cells making up pixels (lit or unlit). It means red, green and blue pixels lit the whole time. Experience shows that this is undoubtedly the most common defect.
To find the total number of defective pixels allowed, just add up the defects of Type 1, 2 and 3.
Type 4 (Fault cluster): the number of defective pixels in a square of 5x5 pixels on a panel.
ISO13406 standard stipulates the number of malfunctioning pixels and the type of defects allowed per million pixels on the panel as shown in the below table.
 
Table 1----Definition of Fault Classes

 

Maximum number of faults per type per million pixels
Class
Type 1
Type 2
Type 3
Cluster with more
Than one type 1or type 2 faults
Cluster of type 3 faults
I
0
0
0
0
0
II
2
2
5
0
2
III
5
15
50
0
5
IV
50
150
500
5
50

 

RONBENs digital photo frames fits ISO13406-2 norm in Class II
Class II is the common class for consumer equipment.
Class I is for Military, Hospital or other Critical applications 
 
Here is the interpretation of the information above, lets take the example of one 8 inch digital photo frame with resolution of 800x600 pixels. The total number of the pixels is 480,000, less than one million. So there can be maximum of:1 lit pixel (type I ) +1 unlit pixel (type II )+3 defect subpixels(red,green or blue) or no more than 2 defect subpixels (red, green or blue) in a cluster of 5x5 pixels.

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