 |
The Samsung PN50A760 produced deep blacks, although it's whites could have been brighter, a not uncommon problem for plasma displays. We also saw the wide variance in brightness on the screen as the percentage of white displayed changes, another issues with plasma televisions. All of the testing in this section was done with DisplayMate, which you can read more about in our Performance: Summary section.
|
 |
Black Level (8.48) 
We measured the deepest black of the Samsung PN50A760 at .08 candelas per meter squared (cd/m2). This is a very good number, reinforcing the reputation that Plasma televisions have for producing deep blacks. You can see below that amongst our comparison televisions only the Panasonic Viera TH-46PZ8OU, another plasma display, beats out the PN50A760. The other two televisions have a significantly higher black level, with the Vizio SV470XVT in particular coming in at over five times brighter than the Samsung PN50A760.
Peak Brightness (6.36)
Like most plasma displays the Samsung PN50A760 doesn't get quite as bright as LCD televisions. We measured the maximum brightness of the PN50A760 at 170.92 cd/m2. We should note that the peak brightness of a plasma television like the PN50A760 varies widely depending on how much of the screen is taken up by white, This is because it takes a lot of power to produce a bright white and plasma televisions have hard ceilings on their total power usage as they use a lot of power and can get really hot. The real impact of this hard ceiling can be seen when you compare the peak brightness with different percentages of white on the display, as you can see in our White Falloff test below. For purposes of peak brightness we use the number from the 20% white screen as this is a good approximation of the amount of white you'll see in the typical scene.
Contrast (7.34)
The contrast ratio is simply the peak brightness divided by the deepest black. We measured the Samsung PN50A760's contrast ratio to be 2137:1. Contrast ratio is one of those numbers that manufacturers like to throw around a lot, and you may notice that our measured contrast ratio is far below Samsung's published number of 1,000,000:1. The discrepancy can be explained by differences in the way that we and manufacturers measure peak brightness and black level. We try to use numbers that will best reflect your actual usage of the television. Manufacturers tend to inflate their numbers by doing things like turning the screen off completely to measure the deepest black and using a 4% white screen to measure the brightest white.
Tunnel Contrast (8.94)
In this test we look at how well the black level on the screen holds up as the percentage of it is steadily decreased. Some displays can see significant increases in the brightness of the deepest black when there are a lot of other bright colors around it. The Samsung PN50A760 did a reasonable job in this test, below you can see a graph of the black level against the percentage of white on the display.
You can see that although there was a slight increase in the deepest black it wasn't huge. You also need to realize that as the percentage of black on the display gets progressively smaller and the rest of the screen gets taken up by white it's almost impossible for a display to hold the black level completely constant. Given these constraints we're quite happy with the Samsung PN50A760's performance here.
White Falloff (5.23)
This test is pretty much the opposite of the one above. What we're looking at here is how the peak brightness varies as the percentage of white on the screen changes. As you might expect from our brief conversation above it varies quite a bit with plasma displays like the Samsung PN50A760. Below you can see a chart showing you exactly how much it varies.
 |
 |
You can see that the power constraints that plasma displays are under are tested the most when white takes up the entire display. The result is that this is the situation where you get the lowest brightness, coming in at just 72.66 cd/m2. As the percentage of white decreases, however, the brightness increases, ending up at 232.27 cd/m2 when the screen is 5% white. Unfortunately this behavrior can have some annoying real world impacts. For example if you're watching a scene with a lot of white in it, say polar bears playing in the snow, you'll notice the brightness of the display fall significantly. It's worth noting that this is not a problem shared by LCD televisions, something you may want to consider if you're a fan of arctic documentaries.
Uniformity (8.25)
Here we look at how uniform the display of the Samsung PN50A760 is. We noticed some cross hatching in areas of a black screen and to a lesser extent a white screen. We also noted some issues with what is commonly known as burn-in. This is an innacurate term that often refers to two different issues. The first is uneven aging of the pixels. What happens here is that pixels age naturally and become less responsive over time. The second is known as latency. In this case the impurities in the elements of the display are redistributed. In both cases you see the result if you have part of the display work harder than other parts, for example if you have a logo displayed in the same place for an extended period of time.
With the Samsung PN50A760 we noted some latency issues where a logo on our computer desktop showed up as a ghost even when we were displaying something different. We know it was a latency issue because the ghost disappeared relatively quickly after the impurities redistributed themselves again. With aging issues it would take much longer for other pixels to catch up in the aging curve. Latency issues are not that big a deal, but it does mean that a plasma television like the Samsung PN50A760 probably isn't a good choice for a computer monitor or a display monitor.
Greyscale Gamma (9.48)
In this test we look at how well the television reproduces the greyscale curve from white to black. The human eye actually notices differences in greyscale in ratios rather than linearly, so we look at the slope of the gamma curve logarithmically rather than linearly. Below you can see the gamma curve for the Samsung PN50A760 plotted logorathimically.
Our ideal for a gamma curve is a slope of between 2.1 and 2.2, which is indicated by the blue line on the graph above. The Samsung PN50A760's gamma curve was actually quite close to this ideal at 2.29. This is excellent performance, but there could be some issues that become more apparent when we graph the gamma curve linearly as you can see below.
What you'll notice here is a lot of bumpiness in the curve. This may indicate some problems with making greyscale transitions in some places, particularly at higher intensities. We did notice some processing issues with certain greyscale patterns and this may be what is happening here, or it may be related to the variance in luminance as the screen gets brighter due to the power limitation issues as we discussed in the white falloff section.
Resolution Scaling (8.25)
Although the Samsung PN50A760 is capable of natively displaying 1080p content, the reality is that the vast majority of content you'll display on the screen is going to be at a different format. Generally speaking 1080p content is only available from Blu-Ray discs. In this section we look at how well the display handles these other formats.
480p (8.35)
This is the format used by DVDs and many standard definition broadcast television channels. One of the most obvious issues you'll notice with 480p content on the Samsung PN50A760 is that the screen doesn't scan properly, cutting off about 3% of the screen on every side. We played around with the PN50A760's display options but weren't able to get rid of this overscan issue. Aside from that we didn't notice any major issues.
720p (7.90)
720p is used a lot by sports broadcasts. This is because it produces smoother motion than 1080i, which is interlaced and we'll discuss further below. When viewing 720p content on the Samsung PN50A760 we noticed some overscan issues, just like we did with 480p. In this case we saw 2% of the display on every side cut off. There were no issues with Moire patterns or legibility but we did notice some light/dark banding in high contrast patterns with alternating black/white lines.
1080i (8.50)
The vast majority of "high definition" television is broadcast in 1080i. This has the same resolution as 1080p with 1080 lines from the top to the bottom of the screen, but in 1080i you alternate between displaying 540 lines at a time. This produces lower signal bandwith, which is why broadcasters like it. Unfortunately it also produces some potential problems with motion artifacts and resolution, which is why sports broadcasts tend to use the smoother 720p format. Thankfully we didn't notice any of these issues with the Samsung PN50A760 when displaying a 1080i signal, which should mean that you'll get a high quality picture out of broadcast HD content, just not quite as good as what you'll see from true 1080p content.
|
