The CCFL LCD TV Option
Despite originally being developed for relatively static computer display use, LCD TVs lit by CCFL (Cold Cathode Fluorescent Lamps) have achieved exceptional commercial success since Sharp introduced the first ones.
Indeed, most key brands – Sony, Philips, Sharp and Toshiba to name but four – have now ditched plasma entirely in favour of LCD TV, and even plasma-loving Panasonic now does LCD options up to 42in.
The majority of LCD TVs continue to be built around the original CCFL lighting concept rather than the recently introduced LED alternatives we’ll get to presently.
LCD screens comprise panels of tiny light valves and regulators. A coloured filter sits in front of each valve, and in the case of the category of LCD we’re looking at here, a single, always-on bright CCFL backlight sits behind each valve (or cell). Each of these cells has its own opening and closing control system with which it decides the amount and polarity of the light that goes through it, and thus the part each cell plays in producing the final picture.
Using simple CCFL bulbs behind LCD panels is by far the simplest, most cost-effective way to produce a flat TV, particularly at relatively small screen sizes.
Light Consistency versus LED
While both edge and direct LED-lit LCD TVs all tend to have problems achieving light consistency right across the screen, it’s generally less troublesome with CCFL LCD TVs (though there are well-documented exceptions).
CCFL-lit TVs generally have no trouble at all pushing out pictures with plenty of brightness and colour aggression.
No Screen Burn/Image Retention or Fizzing
We’ve yet to see a CCFL LCD TV suffer with either of these plasma foibles. Where a CCFL LCD image looks grainy or bitty, it’s down to the picture processing not the core LCD technology.
Black Level Response
As film buffs, we love TVs that can produce a convincing black colour to do justice to all our favourite scary scenes. But sadly this is something CCFL LCDs struggle to achieve.
The reasons for this are easy to understand. For CCFL LCD TVs illuminate their entire array of LC pixels from a single, always on light source. So clearly the ability to regulate the brightness level of individual pixels is limited, resulting in pictures that should look black tending to look grey and cloudy instead.
To try and get round its inherent black level problems, nearly all LCDs employ dynamic contrast systems, where the output of the CCFL light is reduced when the TV’s processors detect that a source picture contains dark content. But while these systems certainly do improve perceived contrast, they can also produce noticeable 'skips' or jumps in the image’s overall brightness level.
Limited Single-Frame Contrast
When showing pictures containing a mixture of bright and dark content, the CCFL LCDs continually have to find a balance/compromise between reducing the brightness of the light parts of the picture in a bid to produce the dark parts convincingly, and reducing the depth of the dark areas so as not to completely remove all the punch from the bright bits.
Limited Viewing Angle
CCFL LCD’s reliance on a single light source behind the LCD array means that the light emitted from the screen emerges with a pretty small angle of dispersion. So images tend to lose contrast and colour quite drastically when watched from angles of 40 degrees or more - a potential real concern for people with large families or tricky room layouts.
Panasonic and Hitachi’s In-Plane Switching (IPS) LCD screens improve this problem quite a bit, but still not to the same level possible with plasma.
Relatively Poor Response Times
The opening and closing element of LCDs means they struggle to respond quickly enough to changes in image content, leading to moving objects potentially looking low on resolution or smeary - or both!
Response times have been massively reduced over the years through a combination of mechanical and processing power improvements, but there are still few if any LCD TVs that are completely immune to motion problems. This is especially true with basic CCFL-lit models, with their largely static backlighting.