Do Yellow Pixels Really Enhance Display Performance?

Who cares? Trying to hold out a little longer with technology that is about to become obsolete. LCD's are on their way out. LED's will soon be cheaper (may already be) and are far better.

This is another question with no single answer. It is possible that the addition of yellow pixels can enhance the color range of an LCD screen, the fly in the ointment is that the color adjustments are somewhat critical in nature and if not done properly, the net color can actually be worse. Yellow pixels are nothing new, they have been debated and fiddled with in the lab for some years, but Sharp is the first brand to try and bring them to mass consumer products.

Despite what the ad hype claims, CRTs were and still are the standard for color rendition of all display technologies. None of the current crop of technologies can match a properly setup CRT display and that includes the next generation of LED screens. The closest competitor is the DLP display system from Texas Instruments which achieves roughly 70%-75% of the color range of a CRT. The jury is still out of the yellow Sharp but I rather doubt it will be any better (and probably not as good as) DLP. LEDs do have a reasonably good advantage (life span and light output) over LCD and plasma technologies, it remains to be seen if they can match DLP or exceed it. I cannot say that any of these technologies will replace the exceedingly large color range of a CRT any time soon. In this respect, tubes still rule.

Maybe the definition of pixel changed and I didn't realize; but in the old days it used to be compossed of three segments: Red, Green and Blue, so the addition of an extra element will be more noticed by the fact that it reduce the density of pixels per square inch (thus "coarsen" resolution) than any improvements on the color output.

If what they mean is to add 1 yellow pixel for every other conventional pixel, then it gets worse, unless they stretch the size of the display to make them fit.

I absolutely agree, nothing beats the old CRT, it allows a whole lot of more fast changing frames per second than the best of the LCDs (you can even see trailing shades of moving objects in these SLOW screens).

Yahlasit

There are various ways to set up the pixel arrangement. The most common way is an RGB triad but there have been LCDs with quad arrangements before, mostly RGGB or RGWB - with an 'extra' green or white (clear) sub-pixel. The sub-pixels per millimeter is increased to yield the same number of pixels per millimeter, if needed.

By the way, most digital cameras have an RGGB quad filter over the detector array; this is called a Bayer filter. The picture signal is processed to reproduce as an RGB triad pixel arrangement when displayed on the camera's LCD screen or displayed on a monitor.

In 2000 Clairvoyante (since acquired by Samsung and renamed Nouvoyance) created the "Pentile" arrangement that used RGBW in a non-quad layout.

No!
It's prob' like the test they did with High Definition TV vs ordinary TV.
Everyone thought the HD was much better....
Only catch is the two TVs in the test were the same.
Del

Really, I didm't hear about that test.

Who says marketing isn't worth anything. A placebo can cure anything.

A placebo can cure anything.
I find two of the big orange ones works best.
Del

'That picture lacks focus Claude!' said the color blind man. 'The grey ones work best for me ... anyway, that is my impression.'

There is some gain from adding a yellow pixel, but demonstrating that improvement requires a color space diagram that includes an axis for luminance. The CIE Uniform Color Space diagram shown below doesn't demonstrate the improvement -- but you must remember that the ordinary CIE diagram doesn't show the color Brown.

The difference shows up when brown and shades of brown need to be displayed. Yes, mixing Green and Red produces Yellow, but when the eye perceives color the intensity of the color and the intensity of the background affect the perception of that color. The Red + Green mix may look yellow in some conditions, but it may look muddy brown in others. Adding a yellow LED would probably improve the appearance of the colors such as gold and tan, as well as some shades of orange and pink. (I haven't seen the display yet, but I read about it a while back.)

It is true that NTSC is the standard, but that's due to the long maturity of CRTs and the TV industry. Newer LCD-based displays with Red, Green and Blue LED backlighting can produce wider color gamuts that the NTSC standard. This is shown in the diagram below. (It should be noted that this is for a dark environment. In bright ambient conditions LCDs win hands-down easily beating CRTs, Plasma and OLEDs.)

LEDs are not likely to replace LCDs as the primary display for TVs; maybe OLEDs will someday, but they have a long way to go.

While the CRT is not the brightest display, compared solely on its wide range of color fidelity (which exceeds the NTSC standard, NTSC has nothing to do with it), frequency response, contrast ratios (CRTs are black, period, no other technology comes close) and longevity (average life is at least 20,000 hours or more, LEDs are approaching this limit but only because of automatic circuits which keep increasing their intensity to compensate for gradually decreasing output over their lifespans). CRTs wear out because of the cathodes in their electron guns, not because the phosphors give out. LCDs are severely hindered by their florescent back lamps and poor lifespans, LEDs are replacing them (finally). Plasma actually can consume more power than a CRT and have problems operating at higher altitudes. DLP with LEDs probably come the closest in color fidelity but still fall short and none of the 'new' technologies have the speed of CRTs.

While the competing technologies all have some attributes, they all still fall short of the grand old CRT when comparing apples to apples. One more thing, CRTs can also beat them in the resolution department as well, 1080i doesn't strain them at all.

A lot of your praise of the CRT is well founded. There are some aspects of a CRT that can't be beat -- though as it turns out, aspect-ratio is one of them. It is a real challenge to build a 16:9 aspect ratio CRT, especially one that competes in size with the latest LCD and plasma displays.

Properly set up, a CRT in a dark ambient gives really black blacks. A plasma display comes close. The newest wide-viewing angle (PVA, IPS...) LCDs that use LEDs and dynamic backlighting can get pretty close, too. In most room environments where the lighting is dim rather than black, LCDs are as good. In brighter environments, especially full sunlight, LCDs win.

Regarding the comment about resolution, although you can theoretically drive the electron beam with infinite resolution, the combination of the gaussian beam width and the dot-matrix structure limits the practical resolution to less than 1080i.

I agree that there are physical limitations to the CRT, but there is no argument possible that black on a CRT, whatever the ambient light conditions, is still as black as can be achieved. A person's visual acuity is not the question here and I have seen picture tubes with a very effective masking of the surface which nearly eliminated reflections on the screen (I have one of those tubes). Direct sunlight on any display reduces its effective viewing.

The electron beam(s) in a picture tube can and have been made quite small, contrary to some statements, CRTs are still being developed and improved, granted they don't have the market like they used to, but they are not dead. Some of these newer types can and do exceed 1080i resolutions (no, they are not being used in TVs). The CRT is still superior for a number of niche markets and will not be displaced any time soon.

However, we are digressing from the original question, which was whether or not yellow pixels can add anything to the display's capability of color range. As I said before, that is a very qualified maybe. The CRT is still the king of color in displays even withstanding what shortcomings it has otherwise.

Are we need photography diectly from screen.

No limits to un-neccessary details consuming lot of bandwidth.