CCFL backlight longevity

By chance i stumbled onto an article on wiki regarding the CCFL backlight on LCD, which said that operating the LCD at below maximum brightness can actually degrade the longevity of the CCFL tubes. I always assumed that opposite is true, so i tend to dim my backlight thinking that i am doing it a lot of good and will make it last, but proves to be quite the opposite. Food for thought.

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Extracted from wiki article. http://en.wikipedia.org/wiki/Cold_cathode

However, CCFLs are strictly limited in the degree to which they can be dimmed, both because a lower plasma current will lower the temperature of the cathode, causing erratic operation, and because running the cathode at too low a temperature drastically shortens the life of the lamps. Much research is being directed to this problem, but high-end manufacturers are now turning to high-efficiency white LEDs as a better solution.

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Very interesting! Another reason why I'm glad I opted for an LED backlight on my T400.

 

I'd take an IPS over a LED every time, even if I have to replace the LCD every couple years.

 

I will only buy LED backlight going forward. The non-led screens fade after a few years, and it's not worth it to replace it (in my experience; I can buy a new laptop for the cost of a screen.)

 

I have 3 CCFL screens - one 9 years old, one 5 years old, one 6 months old. So far they haven't degraded since purchase. I set to turn off the screen when not in use.

 

My old laptop CCFL screen is ~5 years old and it's crazy when I see how dim it is. I didn't notice it when I was using it, since it was a gradual decrease in brightness. After using new laptops with both LED and CCFL backlights, I can't believe how dim my old CCFL screen looks. I'll check when I get home, but right now I'd have to say that the old CCFL on full brightness is around the level of my LED (standard nit) at half brightness, which isn't even all that bright.

 

My X31 have suffered a CCFL backlight failure. Also i think the IPS can be equipped with LED backlight as opposed to the CCFL backlight.

 

CCFL have mercury as compared to LED which doesn't. So this is one reason i will be using more LED equipped LCD in the future.

 

That's an interesting point - I always thought that dimming a screen below max brightness would extend its life.

 

The above quote doesn't say outright "running at reduced brightness reduces the life". The hard data I found says the exact opposite.

I was recently researching ways of extending LCD backlight life, and came across the same mention in Wikipedia, which concerned me. But I later concluded that this temperature issue only applies when running the LCD with really low ambient temperature, for example a display always operating in a below-freezing environment. Such a limitation prevents use of CCFL-backlit LCDs in harsh environments.

The temperature curve is such that below around 20 C, the life starts to shorten. When operating, the bulb heats up, so the ambient temperature can be well below 20 C without degrading life. Also, regarding current, modern backlight dimmers use pulse-width modulation (PWM) for lower dimming, rather than reducing current, because reducing current would lead to erratic operation. They basically flash the bulb on and off a few hundred times a second, and vary the length of each flash so that the average brightness is reduced as desired. In the linked blog posting there are links to further documents data which show that dimming via PWM is equivalent to running at the equivalent lower current, except without any erratic operation. Thus PWM dimming lengthens the life of the bulb, without any negative effects. There are graphs showing that, where they tested bulbs left running continuously for years, some with PWM dimming, and measured the reduction in light output.

 

Gee, who would ever think something on Wikipedia might be factually correct but misleading in its interpretation?

 

For technical subjects it is usually pretty good. This isn't anything political.

 

Thanks for the heads up on this. I didn't look into this issue at great at length. Really appreciate the more detailed information that you provided regarding this issue. Now i can go back to old way of dimming the LCD backlight to save my old CCFL.... LED all the way.....

 

Indeed, LED is the future. But I'm no expert on CCFL either, so my analysis might be wrong. I wish I could find some definitive statements from those in the industry, with references to data to back it up (not just "oh don't worry about it"; not good enough for me).

 

The problem may be that manufactures won't likely release said info until CCFL's are no longer produces. Everyone knows they have a limited lifespan, but those in the industry would not want to hurt their sales of their products. Especially now that CCFL LCD TV's are a ton cheaper than LED (assuming they are clearing out old stock).

 

CCFL's are typically replaceable in TV's though right, and they should last a long time?

Can they be replaced in the Lenovo as well?

I'm havinng some problems with the brightness in my X61s which I have hardly even used since it was new, it has about 1/1000th of the usage of my TV which has no issues for years now.

 

yes you can replace them... that is how some people fix their broken CCFL light.... it is not that easy, but doable.