Samsung LN-T4681F

Editors' Note 04/30/2009: This product has been discontinued, but CNET is continually reviewing current LED-backlit LCD TVs.

Editors' Note 04/29/2008: The rating on this review has been modified from 8.3 to 8.0 due to changes in the competitive marketplace.

Among that tiny segment of the population that cares about the latest HDTV technology, and the even tinier segment that can afford it, the introduction of Samsung's 81 series of flat-panel LCDs is kind of like early Christmas. The first widely distributed LCD HDTVs to incorporate LED backlights--Sony sold a few Qualia 005s a couple years ago at $8,000 to $15,000 a pop--the Samsungs promise amazing black levels, claiming a contrast ratio spec of 500,000:1. The subject of this review, the 46-inch LN-T4681F, does indeed offer the amazing ability to basically disappear in a dark room when displaying a dark scene. That's a tremendous accomplishment for any display, but in the end it's not quite enough to earn our highest praise, because the TV's poor off-angle performance and shiny screen hobble its real-world picture quality in the face of stiff competition, especially given its premium price point. Those issues aside, there's no doubt the Samsung LN-T4681F will make videophiles who can afford it grin with pleasure every time the screen fades to black.

Design

Touch-sensitive controls are mounted on the dark gray strip outside the clear acrylic speaker deflector.

Leave it to Samsung to put together yet another ultrasleek HDTV. The LN-T4681F continues the company's trend of clothing its panels entirely in glossy black, although this model takes things a step further with a few noteworthy accents. The most noticeable consists of a pair of vertical clear acrylic strips running along either edge of the panel. Cupped to deflect sound from the side-mounted speakers into the room, they also serve to support another pair of vertical strips, these made of solid dark gray material that seems a bit out of place among all that gloss.

The overall effect, especially considering the rather wide expanse of glossy black frame between the screen and the clear strips, is of a very wide HDTV; an effect that's further enhanced by the relatively narrow top and bottom sections of the frame around the screen. All told, the LN-T4681F measures 48.4 by 29.6 by 12.6 inches and weighs about 77 pounds including the swivel stand; sans stand, it measures 48.4 by 27 by 4.4 inches and weighs 66 pounds.

Above the post for the swivel stand is a slick LED and touch-sensitive power control.

Unfortunately the LN-T4681F is saddled with the same shiny screen we complained about during our review of the LN-T4665F. While it catches the eye on the sales floor and lets you check your hair, those benefits are outweighed by its distracting reflectivity under normal room lighting (see Performance).

Samsung's remote is almost the same as last year, and we generally found that the slender wand was easy to operate. Only the keys for volume, channel, and device control (the universal clicker can command four other pieces of gear) are illuminated, but that's better than most TV remotes, which skip backlighting altogether. All of the buttons are nicely separated and differentiated, with the exception of the secondary controls clustered at the clicker's base, which kind of blend together. We'd like to see dedicated buttons for each input, although because the set automatically senses and skips inactive inputs, cycling between sources is less arduous than usual. The menu system is easy to navigate, and we appreciated the text explanations that accompanied the selections.

Features
The reason the Samsung LN-T4681F costs significantly more than any LCD TV at its screen size has to do with its backlight. On flat-panel LCDs, the backlight is what powers the picture, and it's generally made of cold-cathode fluorescents (CCFL). Using light-emitting diodes (LED) instead supposedly improves color reproduction over standard LCDs and cuts power consumption somewhat, but by far the most important improvement comes in the form of black-level performance. That's because individual sections of the backlight can be turned off independently and completely, a process Samsung calls "local dimming." As a result, black parts of the picture, such as the void of space or letterbox bars, actually look black instead of the darker gray typical of many flat-panel displays. See Performance for details.

A menu option lets you disable the local dimming of the LED backlight, but why would you want to do that?

Although many LCD HDTVs this year offer a 120Hz refresh rate, the LN-T4681F refreshes its image at the standard 60Hz. In comparison, the less-expensive, non-LED-backlit LN-T71F series refreshes at 120Hz. We haven't seen many benefits of 120Hz by itself, although we have seen some marked improvements caused by antijudder technology, which the 81F also lacks. The set does include a feature called "LED Motion Plus," which, according to Samsung, cycles the LED backlight in eight horizontal sections, once every frame in sync with the LCD, to avoid illuminating LCDs when they're turning off, and thus eliminating "a majority of visible image lag." That sounds well and good, but we encountered a quirk with this feature that discouraged us from engaging it, although this quirk is eliminated with the latest firmware.

Other picture adjustments abound on the LN-T4681F. We liked the ability to adjust the three picture modes independently for each input, allowing us to customize each source with three different groups of picture settings. Only Movie mode allows full adjustment, however, so we recommend using it for the most demanding viewing conditions.

The Detailed Settings menu includes advanced options like gamma and white balance.

In addition to the five presets for color temperature, there's a full set of detailed color temperature controls. Labeled "white balance," they offer both gain and offset adjustments for red, green, and blue, which allows more advanced users to really zero in the set's grayscale. The My Color control, on the other hand, doesn't seem to do much of anything helpful, so we left it in the default positions. The selection of secondary picture controls includes items labeled "black level," which affects shadow detail; dynamic contrast, which adjusts black level on the fly; gamma, which affects the rate of progression from dark to light; and a selection for color gamut, which controls the range of colors the display can reproduce.

We appreciated the solid collection of aspect ratio controls, which include four choices for HD sources. Just Scan is our favorite because it introduces no overscan and does not scale 1080i or 1080p sources, preserving the dot-by-dot match to the TV's native pixels. Standard-def sources allow four choices, as well, including two zoom modes you can adjust vertically to see subtitles or obscure tickers, for example. The Samsung also has a picture-in-picture function that allows it to display two programs at once.

The setup menu controls include, among other items, the energy-saving function of the LN-T46681F. You can choose from four different energy saver modes, which limit peak light output (backlight intensity) to conserve power. As promised, even at full strength the LED backlight does consume less energy than most traditional CCFL backlights we've tested, and the "local dimming" function has the added benefit of cutting power consumption during darker scenes--much like a plasma (see The Basics of TV power for details). The LN-T4681F consumed just a bit less power (about $2 per year) than the former champ, the 46-inch Sony KDL-46S3000 in its default setting. See the Juice Box for complete details.

The LN-T4681F includes two rear-panel HDMI inputs in addition to the standard PC and component inputs.

Like many 2007 HDTVs, the Samsung LN-T4681F offers three HDMI inputs, as opposed to just two, and all are HDMI 1.3-compatible, for what it's worth. Two are on the back, while a third can be found in a recessed bay along the panel's left side. The Samsung's commendable connectivity continues by including a pair of component-video inputs; an AV input with S-Video and composite video; two RF inputs for cable and antenna; and a VGA-style RGB input for computers. That recessed bay offers an additional AV input with S-Video and composite video, a headphone jack, and a USB port that can interface with thumb drives to display photos (JPEG only) and play music (MP3 only).

On the side panel there's a third HDMI input plus a USB port for digital photo display and MP3 music playback.

Performance
It's not a stretch to call the Samsung LN-T4681F's picture quality a breakthrough. For anyone sitting in the sweet spot in front of the set, watching in a dark room, it delivers better overall picture quality--namely black levels and color accuracy--than any HDTV we've tested so far. What prevents it from earning our highest praise is its performance to people sitting to either side of the sweet spot and, to a lesser extent, viewing the TV with the room lights on.

Setup: We began as always by setting up the Samsung LN-T4681F for optimal image quality in our completely darkened theater. After setting maximum light output to a comfortable 40 FTL and adjusting black levels accordingly, we tweaked the set's white balance controls to closer approach the standard of 6500K--although the default Warm2 setting measured relatively close to begin with. After calibration the grayscale measured relatively linear, although it did dip a bit into red in very dark areas.

As we mentioned above, we also noticed one unusual issue with LED Motion Plus. Engaging the feature automatically pegs the backlight control at the maximum setting. In and of itself this isn't a big deal because on the LN-T4681F, as opposed to conventional LCDs, you can still achieve optimally dark black levels with a high backlight setting since the backlight actually turns off (and you can set maximum light output using the contrast control, so you don't lose any adjustability). The problem is that when we turned off the TV while LED Motion Plus was engaged, then turned it back on again, maximum light output jumped from our ideal 40 FTL to about double that, without us touching an adjustment. Weirdly, simply selecting LED Motion Plus in the menu, without even turning it on or off, was enough to re-attenuate the backlight back to 40. Because we didn't want to have to remember to do that every time we turned on the TV, we decided to leave LED Motion Plus turned off. We don't consider that a big loss anyway since we had a difficult time spotting image lag even with the feature turned off.

(Update 12/10/2007: Since this review first posted, Samsung sent us a firmware update that resulted in the TV maintaining its Motion Plus setting. Click here or scroll down to the tips section of this page for details, which also includes a tip detailing our full user menu settings.)

After getting every setting to our liking we sat down to compare the Samsung directly with a few other HDTVs we had on-hand, including Pioneer's PDP-5080HD and PRO-FHD1 as well as Samsung's own FP-T5084--all 50-inch plasmas--along with a pair of LCDs: Sony's KDL-46XBR4 and JVC's LT-47X898. We slipped Transformers into our Toshiba HD-XA2 HD DVD player and sat back to see how the LN-T4681F stacked up.

Black levels and color: Here's the pull-quote: The Samsung can produce the deepest shade of black of any flat-panel HDTV we've tested, regardless of technology. When the screen faded to black or showed a mostly-black background in our completely dark, black-walled test lab, the TV basically disappeared. That's because the LED backlight actually turns off when there's nothing on the screen, whereas the other plasmas and LCDs in the room still emitted light. Screens rarely stay black for long, however; what really matters is a TV's black-level performance with actual program material. To gauge that we compared the Samsung directly with our current reference for black level, the Pioneer PDP-5080HD.

Black areas in most scenes, such as the letterbox bars above and below the picture, the void of space around the spinning Cube during the Transformers intro, and the shadows under the wing of the troop transport plane and in the depths of the cabin, for example, appeared slightly darker on the Pioneer. Don't get us wrong; the difference wasn't night and day (or even 10 p.m. and midnight), but when we paid careful attention to both over the course of the movie, the Pioneer did win in most cases. We could coax a deeper black out of both sets by reducing their brightness controls, of course, but doing that obscured details in shadows. The Sony, for its part, still managed to display a respectable level of black, but it was slightly outpaced by the other two. Those three HDTVs, in turn, produced better black levels than the other sets in the room. To sum it up, while the Samsung definitely produces the deepest shade of black in isolated circumstances including mostly black scenes, the Pioneer still holds the crown for best overall black-level performance with the majority of mixed-brightness program material.

A quick aside for the geeks: The discrepancy between the Samsung's black levels showing a fully black screen vs. real program material was supported by further testing. For instance, the Samsung's black screen was immeasurable by our KM CS-200. However, when we looked at a standard checkerboard pattern--which includes both white and black, and so better represents actual program material--the Samsung's blacks were not only measurable, but lighter than the Sony's and the Pioneer's. We suspect the main culprit here is blooming (see below), where the bright white squares next to the darker ones spoiled that absolute black. Either way, these objective tests jibe with our subjective experience, which is that the Samsung gets extremely dark on full-black screens, but that performance doesn't translate to the very best black-level performance with most program material.

Back to Transformers: As the sun set on the tarmac after the mysterious chopper lands, we had a good opportunity to appreciate the Samsung's superb shadow detail. For example, we could make out the camo of the shadowed soldiers and details in the Decepticon's jet engine; it all looked quite natural yet packed with the punch only great contrast can deliver.

We did see one small fly in the black-level ointment, however. The LEDs produced what's known as "blooming," when a bright onscreen item exceeds its boundaries and brightens the dark areas immediately adjacent. When the Transformers title came up in a field of black, for example, or when Earth spun around to be cut off by the black letterbox bars, the black areas next to the lettering and the planet brightened in comparison to the other sets in the room, which exhibited no blooming. In most scenes, however, blooming was difficult to detect, especially outside the letterbox bars, and we never found it outright distracting except when we watched the set from off-angle. We also expected the Samsung, since its LEDs do vary in intensity, to fail our black-level retention test, but it passed with aplomb after calibration; the levels of black and near-black remained constant relative to one another regardless of the brightness of other areas of the screen (blooming notwithstanding).

The Samsung LN-T4681F evinced superb overall color accuracy, surpassing both the Pioneer PDP-5080HD and the Sony. Its solid grayscale and excellent primary colors combined to rival the color reproduction of the PRO-FHD1, our current color reference, and its black levels contributed greatly to perceived saturation and richness, easily outdoing the FHD1 in overall punch. The grass and trees around the Pentagon and the lake, the blue sky above the choppers in the desert, even Jon Voight's ruddy mug looked natural, realistic and rich, and the ubiquitous midriff of Mikaela Banes looked deeply tan without a hint of sunburn.

Video processing: As we expected, the film looked incredibly sharp and well-detailed, although, as usual, we did not distinguish any difference in detail between the Samsung and the other sets in the room, including the lower-resolution Pioneer, which looked every bit as sharp, from our seating distance of about 7 feet. According to test patterns, the LN-T4681F delivered every line of 1080i and 1080p sources when set to Just Scan mode. Like many sets we've tested, it did not deinterlace 1080i film-based sources properly, and in our one real-world deinterlacing test, the end of Chapter 6 of Ghost Rider, the grille of the RV showed more moiré and artifacts than we saw on sets that passed, such as the JVC and the PRO-FHD1. As always, spotting other instances of the effect of improper 1080i deinterlacing was difficult, and we don't consider this failure a major issue.

(Update 12/10/2007: Since this review has first posted, Samsung sent us a firmware update that resulted in the TV properly deinterlacing 1080i film-based material. Click here or scroll down to the tips section of this page for details.)

We also didn't notice any serious instances of motion blur or image lag during the film, regardless of whether we engaged LED Motion Plus, which supposedly helps prevent such lag if it occurs. Looking at our favorite ESPNHD ticker, the edges of the letters looked a bit softer on the LN-T4681F than on the other TVs regardless of what setting we chose for LED Motion Plus. On other program material we watched, however, the Samsung maintained a sharp image, even during the quick action of a basketball game and the lightning activity of the big set-piece fights in Transformers.

Other performance considerations: All of our observations of LN-T4681F's picture quality were made, as usual, from the sweet spot directly in front of the TV with our eyes lined up with the middle of the screen. From off-angle, however, the LN-T4681F's black levels grew noticeably less black, which, of course, impeded saturation, too. We've seen the same effect on all LCDs we've reviewed, but on the LN-T4681F it was quite a bit more noticeable. When we moved just one seat over on the couch, for example, the letterbox bars and black of space in the opening "Cube" section appeared appreciably brighter than on the Sony seen from the same angle. From extreme angles, the Samsung's black areas looked brighter than any TVs' in the room; blacks on the Sony, again, stayed much truer from extreme angles. The Samsung's blooming effects also became more noticeable when seen from off-angle. Given its poor off-angle performance, videophiles who want to experience the LN-T4681F's best picture quality will have to really duke it out for the sweet spot (luckily that stand swivels!). As always, the plasmas in the room looked basically the same from any angle.

Compared with most other LCDs we've tested, the LN-T4681F exhibited very good uniformity across the screen, although not quite as good as the Sony. Looking at gray-field test patterns, the only issue we saw was a tendency in mid-dark fields (about 25-15 IRE) for the left and right sides of the image to appear brighter than the middle. This issue was difficult to spot in program material, so we don't consider it a big deal.

Like that of the LN-T4665F, the LN-T4681F's shiny screen proved a distraction. We could see ourselves reflected in the screen when the picture showed any moderately dark material while room lighting was moderate to bright. As we type this passage watching an NBA playoff game, for example, the silver strip lining the edge of our laptop, as well as our orange shirt and even the beige universal remote, are visible in any dark areas, including the circle of the Spurs' court and the Blazers' uniforms. None of the other sets in the room, including the plasmas, reflected as much ambient light. We asked Samsung whether the shiny screen had any impact on contrast ratio, and while the company's reps explained that some benefit to the CR spec is derived from the screen's supposed ability to limit interference from ambient light, they said the LED backlight's local dimming was a much larger factor affecting CR. We'd love to see a version of this set without the reflective screen, but we'll probably have to wait till next year for that.

As we've mentioned before, standard-def TV programs can often arrive via a high-definition resolution (depending on your cable or satellite box), which can make a high-def TV's standard-def processing a moot point. For people who do connect a true standard-def source, however, such as the 480i component-video input we used, the LN-T4681F will deliver a slightly below-average performance. It did poorly on the jaggies tests, doing little to smooth out the edges of diagonal lines or the stripes in the waving American flag. While it had no trouble resolving every line of DVD resolution, fine details like the stones in the bridge and the grass appeared a hair softer than on the Sony and the Pioneer, for example. When we looked at HQV's noisy shots of skies and sunsets, we saw that the Samsung's four levels of noise reduction had a very slight impact from one to the other, although in some areas we could discern the benefit of using High as opposed to Off. We still recommend leaving it in Off unless video noise becomes bothersome. Finally the set engaged 2:3 pull-down quickly and effectively, cleaning up the moiré in the grandstand behind the racecar.

With PC sources originating on DVI and connected to the Samsung's HDMI port, the LN-T4681F performed extremely well, as we expect from 1080p flat-panel LCDs. In Just Scan mode the set resolved every detail of 1920x1080 sources according to DisplayMate, with no overscan and excellent sharpness in 10-point text and other fine details. PC performance dropped off a bit when we switched to the set's analog VGA input; while resolution was still full with no overscan, onscreen objects appeared a bit softer, and we detected some interference in the highest horizontal resolution patterns. We were frankly surprised by the dropoff in analog PC quality because Samsung's 1080p sets, both plasma and LCD, are usually superb in this regard, but at the end of the day it won't matter to most users. The analog VGA input is still perfectly serviceable for casual connections, and serious PC users will want to go in via HDMI anyway.

Juice box

Samsung LN-T4681F	Picture settings
	Default	Calibrated	Power Save
Picture on (watts)	194.65	112.57	112.03
Picture on (watts/sq. inch)	0.22	0.12	0.13
Standby (watts)	1.18	1.18	1.18
Cost per year	$59.83	$34.90	$37.77
Score (considering size)	Good
Score (overall)	Good

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