Samsung LN-T4681F 46-inch LCD HDTV 
Home Theater Flat Panel HDTVs LCD HDTVs
Written by Adrienne Maxwell   
Tuesday, 01 January 2008

Oh, dreaded backlight, what a bane you’ve been to manufacturers trying to perfect the evolution of the LCD as a home theater display technology. Sure, you provide the illumination required that produces an image on the screen, but you’re also responsible for LCD’s two primary drawbacks compared with other display technologies: black level and motion blur. Since LCD first crossed over from the PC to the TV screen, designers have experimented with technologies to reduce black-level and motion limitations. In-plane switching changed the orientation of the liquid crystals to block the light differently, in hopes that this would improve black level and viewing angle. The adjustable backlight lets you turn down the light’s brightness to get a better black level, while a flashing backlight can provide the break between frames that your eyes need to reduce motion blur. The hot new thing is the use of a 120-hertz frame rate to minimize motion blur and render smoother motion. While these technologies can be somewhat effective when utilized correctly, several introduce new concerns, and none has been the proverbial “just right one” that effectively deals with both black-level and motion concerns.

Enter the LED backlight. Instead of employing a fluorescent backlight to illuminate the entire screen, some manufacturers are now experimenting with the use of individual LEDs that can tailor light output more precisely to the content onscreen. If implemented correctly, this technology would allow an LCD to perform more like a plasma, which creates light specifically when needed and consequently allows for better black levels and viewing angles. Samsung is one of the first manufacturers to introduce LED-based LCDs to the market in the form of the 81 Series, which includes models ranging from 40 to 57 inches.

Perhaps now is the time for a confession. I’ve reviewed a lot of LCDs over the past few years, and my response to most of the “corrective” technologies described above has been lukewarm at best. While I appreciate the versatility that LCD brings to the table when it comes to everyday TV viewing, it has never been my first choice for home theater use, so it was with great interest that I sat down with Samsung’s 46-inch, 1080p LN-T4681F to see if the LED approach would finally change my mind.

Not surprisingly, the 81 Series is Samsung’s top-shelf line. As such, this 46-inch HDTV costs $3,999, which puts it at the high end of the price spectrum for comparably-sized flat panels. It certainly looks like a high-end display, with a glossy black frame, swiveling stand and thin, slot-style speakers along the side panels. Samsung also incorporates a few stylish touches. Along the lower portion of the right slot speaker are virtual buttons for source, menu, volume, and channel, each illuminated by a simple white LED when touched. That neon-blue ring that wraps around the TV’s base, just beneath the Samsung logo, is actually a power button. If you find this light distracting, Samsung wisely allows you to turn it off in the set-up menu. The TV also produces a very Atari-like sound effect when you power it up or down, another feature you can disable if you wish.

One design element that might jump out at you is the screen itself. Upon first glance, you might think the store sent you home with a plasma TV by mistake, as the screen reflects light. Glossy, reflective LCD screens have become a popular trend in the world of notebook PCs, but Samsung is one of the few manufacturers I’ve seen to go this route with their LCD TVs. While this makes the TV prettier to look at when it’s turned off, it takes away one of LCD’s advantages over plasma: you can put the LCD in a very bright, sunlit room and not have to worry about light reflection off the screen. With my shades open or room lights turned on, I was aware of room reflections on the LN-T4681F’s screen when viewing darker DVD and TV content. Like most LCDs, the TV is so bright that reflections aren’t as much of a concern with brighter content.

The remote control consists mostly of small, similarly shaped black buttons residing on a black base. Add in the fact that only the volume, channel and TV buttons are backlit, and this remote is difficult to use in the dark. It doesn’t have dedicated source buttons, but this TV does sense which inputs are in use and only scrolls through the active ones when you press the Source button on the TV or remote. As for sources, you can connect a lot of them to the LN-T4681F. Video inputs include three HDMI (including one on the side panel), two component video, one 15-pin RGB, two S-video, two composite video and two RF inputs to access the internal ATSC, NTSC and Clear-QAM tuners. A mini-jack audio input accompanies the PC input, while stereo analog audio jacks accompany the remaining analog video inputs. The HDMI inputs do not have accompanying analog audio inputs, but there is an optical digital audio output to send audio to an external sound system. Also on the side panel are a headphone jack and a USB port for utilizing Samsung’s WiseLink photo/music playback system.

The user menu is cleanly laid out and easy to navigate. Should you choose to use the internal tuners, the Channel menu provides a lot of tuning and fine-tuning options. The TV lacks a program guide, but it includes picture-in-picture functionality, with the ability to adjust the shape and position of the PIP windows. The Sound menu includes five sound modes (Standard, Music, Movie, Speech and Custom), plus an equalizer to tailor specific frequencies. SRS TruSurround XT processing is on board, and you can activate the internal mute if you plan to use an external sound system, which I recommend. The slot speakers have solid dynamic ability, but male vocals in particular sound thin and unnatural.

The Picture menu includes just about every basic and advanced control you could want, beginning with three picture modes (Dynamic, Standard and Movie) that you can adjust independently for each input. There are five color-temperature settings (Cool2, Cool1, Normal, Warm1 and Warm2), plus basic controls for contrast, brightness, sharpness, color and tint. I went with the Warm2 color temperature, which produces the most accurate color palette: skin tones consistently look natural with no red push, while darker content does not look overly cool or blue. The TV’s white-balance controls are accessible directly via the user menu should you wish to have the TV calibrated, but I really didn’t feel a need to do so. You can also choose between two color spaces: the Auto mode offers red, green and blue color points that look natural and close to SMPTE standards, while the Wide mode creates the more-exaggerated green that is common to LCD panels. All of the desirable aspect ratio options are here, but the TV lacks automatic aspect ratio detection. You can control the TV’s light output via a 10-step adjustable backlight, as well as an Energy Savings mode – the latter is oddly located in the general Set-up menu, instead of in the Picture menu. Also in the Set-up menu are the Film mode, which automatically adjusts the deinterlacing for film- or video-based sources, and an HDMI black-level setting that lets you select a low or high black level when mating the TV with an HDMI device set for the wider RGB dynamic range level. If your HDMI devices use a YCbCr dynamic range level, the HDMI black-level setting is locked at low. According to Samsung, next year’s LCDs will put these controls in the Picture menu where they belong.

Two video controls deal specifically with the LED backlighting. The first, called LED SmartLighting, addresses black-level issues by employing what Samsung calls “local dimming” technology, meaning that the individual LED backlights react dynamically to the picture content, turning themselves on and off as needed. With an all-black test pattern, for instance, all of the LEDs are off, so you can’t even tell the TV is on. Switch to a scene in which a person’s face is framed against a dark background, the LEDs required to illuminate the face will turn on, while the surrounding LEDs remain completely dark. The TV doesn’t have a 1:1 ratio of LEDs to pixels; instead, each LED handles a small quadrant of the screen. Samsung couldn’t tell me exactly how many LEDs are employed in the LN-T4681F, but you can see the effects of this quadrant design. For instance, in a DVD menu that contains white text on a black background, most of the background will be completely dark, but the area around the white text glows slightly because that whole LED quadrant has to be turned on. So the effect isn’t as precise as a plasma TV that can illuminate each pixel individually. Turning off the LED SmartLighting option in the menu turns on all of the LEDs, providing a constant light source that functions like a normal backlight, which you can raise or lower using the 10-step adjustable backlight. I’m not sure why you’d turn off LED SmartLighting after you’ve paid a premium for the TV, but I guess freedom of choice is a good thing. I should mention that you can still adjust the backlight when LED SmartLighting is on; it will affect the TV’s brightness and the deepness of blacks that you get when the LEDs are in use. I turned the backlight all the way down to ensure the best blacks.

The second control is called LED Motion Plus, which addresses the problem of motion blur. LED Motion Plus causes the LN-T4681F to cycle through the LED backlights, from the top of the screen to the bottom, once per frame. The common theory is that motion blur results from having a continuous light source; the eye needs a break in light output or else it perceives a blurring effect in motion. A flashing or cycling backlight provides that break. However, Samsung gives a different explanation as to why a cycling backlight reduces motion blur. According to a company rep, the continuous light source isn’t the problem; rather, an LCD’s pixel response time is the problem. The pixel response has a slight lag relative to the original signal, more so when the pixel turns off than when it turns on. When cycling the LED backlight, the TV doesn’t illuminate the pixels when they’re off and thus reduces the viewer’s ability to see the lag that would otherwise occur. However it works, let me just say this: it works. My FPD Benchmark Software Blu-ray test disc consists of text patterns, resolution charts, maps and real-world video segments for evaluating the severity of motion blur. With the LN-T4681F’s LED Motion Plus turned on, I saw a marked reduction in blur with all of the patterns I tried. When this feature is enabled, it locks the TV’s light output at a set level, roughly equivalent to setting the backlight at two (of a possible 10).

Television And Movies
I immediately put this LED technology to the test with some of my favorite black-level demo scenes, starting with Pirates of the Caribbean: The Curse of the Black Pearl on Blu-ray (Buena Vista Home Entertainment). When we first meet Captain Jack in chapter two, it was a bright, sunny day, with gorgeous blue skies, majestic seascapes and lots of precise detail to showcase an LCD’s strengths. And the LN-T4681F did a great job here: its great contrast made the image pop, colors and skin tones looked very natural, and detail in both facial close-ups and brick buildings was excellent. But then came the nighttime pirate attack of chapter four, a much more difficult feat for a normal LCD. The LN-T4681F maintained great image saturation in a darkened room and did a very nice job rendering the fine black details in these complex scenes. The effects of LED SmartLighting weren’t invisible, though: at times, I noticed the aforementioned glowing effect around objects, and, during one pan across a dark scene, I could see the black level fade sequentially across the screen as the LEDs turned themselves off. Purists will point out that this local-dimming approach is technically cheating, as the overall black level isn’t really that low. Maybe so, but it’s a pretty effective cheat. It’s not as if the black level is only good when the LEDs are completely off, something I feared would be the case. Using my Gefen HDMI distribution amp, I compared the LN-T46812F’s performance directly with my reference Epson LCD projector, which is capable of great blacks. This LCD more than held its own in terms of image saturation, even in complexly-lit nighttime scenes that required most of the LEDs to remain on.

The same proved true with the standard-def DVD versions of The Bourne Supremacy (Universal Studios Home Video) and The Prestige (Buena Vista Home Entertainment). The LN-T4681F did an excellent job rendering the fine details in dark scenes, and image saturation in a completely dark theater was very good. There were times when my projector’s blacks looked better and times when the LCD’s blacks looked better, but overall, the two were comparable, which is saying a lot for an LCD panel. To remind myself of this fact, I turned off the LED SmartLighting for a while. What I got was a more LCD-like image in a dark room: grayish blacks, a lack of fine shading and black detail, and a generally washed-out picture.

Obviously, those good blacks continue to pay dividends with brighter high-def content, but another benefit of LED SmartLighting is that the TV doesn’t have to limit its light output to produce better blacks. Even at the lowest backlight setting, the LN-T4681F has great light output, so brighter HD content really pops, regardless of whether you view it in a bright or dark room. Scenes from Kingdom of Heaven (Twentieth Century Fox Home Entertainment) and Shooter (Paramount Home Entertainment) on Blu-ray disc had wonderfully rich contrast, while high-def sporting events looked spectacular, thanks to a combination of great contrast, natural color and excellent detail. The green grass in football and baseball broadcasts looked a little off, but wasn’t overly exaggerated or cartoonish. I took in a hockey game on HDNet, switching LED Motion Plus on and off as the camera panned quickly around the arena. With LED Motion Plus in effect, I could easily follow the puck and saw better delineation between the fans in the background.

The LN-T4681F does a nice job of deinterlacing 1080i sources. My HQV Benchmark test disc shows that it correctly deinterlaces 1080i and picks up the 3:2 sequence in film-based sources. I didn’t see jaggies or other artifacts in prime-time 1080i shows like Heroes and Law & Order, or in high-def DVDs output at 1080i from my Sony Blu-ray player. It’s not mandatory that you mate this TV with a good 1080p-capable player, but if you do, the HDMI inputs accept both 1080p/60 and 1080p/24.

The Downside
The one way in which the LN-T4681F reveals its LCD nature is in its viewing angle. Image saturation diminishes when you move even 45 degrees off-axis, but it’s not as dramatic as the drop-off you get with most normal LCDs. The image retains more detail, but you lose the great contrast and color accuracy you get when viewing the TV straight on. As I mentioned, the screen also reflects light, which is another reason to be mindful of where you place the TV in your room.

Because the TV is so bright, I was more aware of compression artifacts in my DirecTV signal. Also, the LN-T4681F’s picture can be a bit noisy through the HDMI inputs, and the digital noise reduction circuitry didn’t offer any clear improvement. The Video Essentials white-to-black ramp (DVD International; title 17, chapter seven) revealed a number of uneven steps in the mid to dark grays. As a result, the smoke that hangs over chapter 10 of the Ladder 49 DVD (Buena Vista Home Entertainment) looked a little artificial, and there was more noise in the darker-colored backgrounds of HDTV shows. This wasn’t excessive, and higher-quality Blu-ray and DVD transfers were generally clean. Add in the fact that the HDMI inputs don’t do a very good job of deinterlacing 480i sources, creating a fair amount of artifacts. Ultimately, I preferred using component video with my DirecTV set-top box, as the picture was much cleaner with both standard- and high-definition sources. HDMI was a better fit with my Blu-ray player, or with a good progressive-scan/upconverting DVD player.

As I said at the start, I’ve reviewed a lot of LCDs over the past few years, and the LN-T4681F is easily my favorite. I’d go so far as to call it the best-looking LCD I’ve seen to date. It delivers that bright, detailed, grabbing image we’ve come to expect from LCD in a well-lit room, yet it’s up to the challenge of a creating a rich, well-saturated image in a darkened theater space. High-definition content can look gorgeous, and the TV doesn’t stumble when asked to handle standard definition. All in all, the LN-T4681F is worth the price premium in terms of performance, versatility, aesthetics and features.

Of the many LCD solutions I’ve seen, LED backlighting is the most promising answer to overcoming common LCD drawbacks like black level and motion blur. Black-level purists may take umbrage with the technology’s shifting blacks, but even they must admit it’s a big step in the right direction. Remember, this is a first-generation LED display; theoretically, it will only get better – and less expensive – as time goes by, which should make plasma manufacturers very nervous.
Manufacturer Samsung
Model LN-T4681F 46-inch LCD HDTV
Reviewer Adrienne Maxwell
Diagonal Screen Size 43 to 56-inches

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