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| The LN-46A750 had excellent performance overall in this section of our review, which looks at the blacks, whites and in between grays that the display can produce. The blacks were deep, the whites were bright and the grays in between them were accurate. |
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Black Level (7.12) 
The deeper the black that a display can manage, the more realistic your favorite horror movies will look. We measured the darkest black of the LN-46A750 at 0.15 cd/m2 (candelas per meter squared; the smaller the number the blacker the black). LCDs create blacks by blocking the light from the backlight, but they can never block all of it; some always gets through. But 0.15 cd/m2 means that only a very minimal amount of light got through, and the blacks in our test sequences looked dark and deep. Although the blacks on this display are not as deep as some plasma displays (the Panasonic TH-46PZ80U, for instance, had a black level of just 0.06 cd/m2), they are pretty black for an LCD display, and they should not detract from your enjoyment of movies that use a lot of dark screens for effect.
Peak Brightness (9.54)
The flip side of the coin here is the peak white; the brighter this is, the brighter the display and the better it will stand up to daylight and other light sources. The LN-46A750 did not disappoint here; we measured the peak brightness at a eye-watering 426.3 cd/m2. That's very bright; easily enough to make the screen stand out from the crowd and to make the screen visible in anything but the brightest sunlight. Of course, that may also be too bright; watch a display that bright in a darkened room and you'll give yourself a serious headache. Fortunately, the display offers 10 levels of backlight control, so you can dial the brightness down for evening viewing, but then crank it up for daytime soap operas.
Contrast (7.91)
This combination of deep blacks and bright white lead to an excellent contrast ratio; the LN-46A750 had an impressive contrast ratio of 2842:1. Higher is better on contrast ratios; that means deeper blacks and brighter whites. That is significantly better than most LCD displays; the Vizio VO47L was nearly as bright, but only managed a contrast ratio of 964:1 as the blacks were not that deep. One thing to note is that this is significantly less than the 50,000:1 contrast ratio that Samsung quotes, because they quote a figure called dynamic contrast ratio, which is where the black is measured with the backlight turned down as low as possible. Unsurprisingly, our figures (which are measured with the backlight at the same maximum level for both black and white measurements) are much lower, but our measurements more accurately represent what you would get in real world use.
Tunnel Contrast (8.57)
In the real world, blacks and white exist alongside each other on the same screen, which is why we measure tunnel contrast. In this test, we measure how well the blacks on screen hold up as the amount of white on the screen increases by measuring a small area of black in the center of the screen that is surrounded by a varying amount of white (see the image on the right for how this works; the small circle is the area that we measure). On some displays, the blacks get lighter as some of the light from the white areas of the screen bounces around inside the display, but that didn't seem to be a problem with the LN-46A750; in our tests, the black stayed pretty dark even when it was surrounded by white.
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The graph above shows the results of our tests, with the percentage of white on the screen along the bottom and the luminance of the black (ie: how bright it is) along the side. As you can see, the black only increased very slightly, even when surrounded by a completely white screen. However, the LN-46A750 is not alone in performing well here; most of the displays that we have tested so far have performed well in this test.
White Falloff (9.46)
Some displays have an annoying habit of getting dim if there is a lot of light on the screen; they either can't handle the heat that produces, or the backlights they use just can't produce enough light. That's why we test how much the luminance of the white drops off as the amount of white on the screen increases; a perfect display would have the same white level if there was a small patch of white or a sea of white on the screen.
Again, the LN-46A750 did well here; the white level did not change significantly as the amount of white increased; it stayed at the same high level all the way through this test. This contrasts with plasma displays such as the Panasonic TH-46PZ80U, where the brightness of the white falls off sharply as the amount of white increased.
Uniformity (7.57)
A good display should have a smooth, uniform look on both black and white screens, and that's what we look for in this test. The LN-46A750 had a couple of minor issues here that cost it a few points; although the black is nice and deep, there was a distinct splotchy pattern on our all-black test screen; there were four patches of slightly lighter black around the center of the screen. This is presumably because the backlights that light the screen are located at these points, and this shows through. On our all-white testing screen, the corners were also a little dimmer than the center of the screen, again presumably because of the location of the backlights. We measured the luminance of the top left corner at 235.7 cd/m2; significantly less than the center. However, the human eye tends to gloss over gradual changes in brightness, and the white screen didn't have any problems with sudden changes in brightness; the shift was gradual from the center to the corner. Both of these issues are noticeable, but they don't really distract from the image quality; we found that both bright and dark sequences looked attractive and did not have any significant problems.
Greyscale Gamma (7.72)
Update: We have rescaled our scoring for this section. The original score was 8.37.
The gamma of a screen controls how the display goes from black to white; the gamma is the shape of the curve of the intensity of the grays in between the two, so it's an important measure for judging the quality of a display. The ideal gamma for a television is between 2.4 and 2.5, and the LN-46A750 fell just outside this range at 2.58. We determine the gamma of a display by feeding it a series of screens of increasing brightness, then measuring the luminance of each screen one by one. The graph of these results is below.
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Because of the way that the eye interprets light, this graph has an exponential curve. It's a little easier to interpret if we plot it on a graph with a logarithmic axis. A perfect display would produce a straight line on this graph, with the intensity of the gray increasing smoothly as the intensity of the gray in the image increases. The blue line on the graph below shows what would be the perfect fit, the black line shows what the LN-46A750 achieved in our tests.
The LN-46A750 did a decent job here; the curve is smooth, and is pretty close to the perfect fit of the blue line. So the LN-46A750 has a good gamma curve; there are no major issues here.
Resolution Scaling (7.37)
The LN-46A750 is a full HD 1080p screen, but it also has to deal with signals that are at lower resolutions, such as the 1080i signals that most high definition cable boxes produce. So, we test how well the display does by feeding it a series of test screen in each resolution and judging ho good a job it does of scaling and processing the images to fit the screen. Let's run through each of the different formats that we test, one by one.
480p (8.05)
480p signals are generated by devices such as DVD players or DTV conversion boxes. the LN-46A750 did a very decent job of processing and scaling these; we found that text was sharp and readable, and that the scaling up did not overly affect the image quality. The images were overscanned by about 4 percent, which is means that the edges of the image were cut off. This is pretty standard with signals of this type, as it is the same way that standard definition TV signals are displayed.
720p (7.55)
720p signals are used by many of the TV networks to broadcast sports, because the progressive nature of the signals produces smoother motion than the 1080i signals that they use for most other material. Again, the LN-46A750 did a very decent job here, with images looking clean and sharp after they had been processed and scaled to fit the screen. There was a slight dithering pattern on some screens, though; screens that used alternating black and white lines had a slight checkerboard look to them. By default, the images were overscanned by 4 per cent, as the display defaulted to the 16:9 aspect ratio mode. This could be a pain if you are using the display as a computer screen, but it can be easily overcome by switching the screen to Just Scan mode, which took two presses of the P.Size button.
1080i (8.25)
1080i signals are what most people think of with high definition; this is the type of signal that most high def set-top boxes and devices produce. These looked good on the LN-46A750, as text was sharp and the fine details of our test screens were well displayed. Images were not overscanned.
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