subject: LED vs. OLED [print this page] Author: Saul Gordon Author: Saul Gordon
Here is a quick rundown for people that feel a bit lost. Answer is: NO!, OLED and LED, are not the same thing! Simply claimed, LED screens are the link between current LCD and the OLED, expected to come out in a few years. Common to all 3 though: images are shown on a slab made of points, juxtaposed sub-pixels actually, red, green and blue.
The Plain Vanilla LCD
Light is emitted by a tube as wide as the display is. There are usually four tubes, either parallel or placed on the sides.
The tube emits light behind the color cells. One can guess from this intentionally simplified illustration, the issue this could produce: the closer more cells are to the tube, the brighter. On this drawing, the top line will be more clear than the bottom one.
This basically raises concerns of color consistency on the screen where variations of 30 pc in light power are commonly found between two points intended to show the same color!
This is not a dead-end. Makers of top-end displays are now more conscientious to light distribution. In some monitors, rare and very pricey, variation did reach 15% between a clear point and another darker one.
The latter thus has a tendency to a dark gray to a particularly told gray for bad screens, instead of precise black.
It is just "magnifique". The consistency is perfect (when the screen is adequatelyly setup), and to obtain an absolute black on a sub-pixel, just switch it off. This let's you play much more finely with colors, at the sub-pixel level , whereas with a tube a whole quarter of the slab is influenced at a time, or five hundred thousand sub-pixels at once (on a Full HD panel) when power is varied.
These are only prototypes and final products are not prepared just yet for the high price . How much would the same 32-inch TV launch at? Beyond any reasonable affordability most likely.
So if OLED is not ready just yet, what's the alternative for now.
LED Screens Now tubes are removed from LCD screens and replaced by white LEDs spread out behind the LCD slab. Making a technology where only the LCD back-lighting has been modified.
But the diagram does show the principal constraints of the backlit LED. The more diodes, the better homogeneity will be. Nonetheless, homogeneity concerns remain.
As with LCD tubes, light leakage thru the black dots of the image persists. It can get better when the monitor notes that the image displayed is dark. It then decreases the brightness of the LEDs that illuminate the dark area. This results in conspicuous changes in lighting from one image to another.
A Light Source For Each Point: The Key To Quality Assuming assume a total of two hundred diodes providing backlighting to a Full HD panel measuring 1920 x 1080 pixels. We would then have 1920 x 1080 = 1778 Mega pixels, or 5.33 million sub-pixels. Each diode would thus funnel light to 5.33 million / 200 = 26,667 sub-pixels per diode. Summarizing:
LED screens, are only equipped with forty-eight LEDs, not 200! Interest is so much less. In LED screens, many have diodes not matrixed behind the cells, but on the sides! The advantage here becomes then pretty much exclusively for selling purposes. Eventually, the dynamic contrasts of LED screens are still unsatisfactory and produce unbalanced pictures, with moving areas of gray like clouds in motion.
A logical progress could then be anticipated. Alas, it is not that simple...
So theoretically, yes, it's better, as long as enough diodes are packed in - and they're regularly lacking - and enhance the dynamic contrasts to make use of the flexibility introduced by LEDs vs. tubes. For now, cutting the dynamic contrast is always recommended on all models of TVs and monitors!
To go further and read some reviews, some users report their opinion of LED monitors and TVs:
