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Posted by Rita Berkowitz on 11/06/07 22:33
Bob Myers wrote:
>> LCD displays don't work without backlights.
>> The most popular backlight so far has been
>> small-form fluouescent tubes (which require
>> ballasts, just like their big brothers.)
>
> Sorry, no; the "ballast" for a cold-cathode fluorescent
> of the type used in LCD backlighting is in the inverter,
> which is a separate dedicated HV power supply
> used solely to drive the CCFL tubes. You may replace
> the inverter, but you don't replace a "ballast" per se.
Even from a technical standpoint that is a mighty fine hair you're trying to
split.
>> The spectrum of even "full-spectrum" fluorescents is rather
>> a significant compromise over reference sources such as
>> tungsten lamps. Traditional fluorescent tubes have a giant
>> green spike (or two). We used to use magenta-color plastic
>> tubes over the fluorescent lamps to try to knock down the green
>> to allow us to shoot film or video. Some professional video
>> cameras (particularly those used by news videographers)
>> have special settings to compensate for fluorescent illumination.
>
> Sure, and that's where I figured Rita B. was going. But
> concerns with fluorescent lighting for room illumination
> purposes are irrelevant re the color performance of a display
> using CCFL backlighting. The only issues there are what
> primary chromaticities and white point you wind up with as
> seen from the front of the LCD; what got you there is, from a
> front-of-screen performance perspective, a "don't care."
And you're not going to get the full spectrum of light at a linear level
with fluorescent backlights.
Rita
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