Black Level, Contrast Performance, and “Black Optimiser”
When we first caught sight of the Samsung PS64F8500 at the 2013 CES in January, we called the performance of the TV “OLED-like”, which was a bold statement that probably caused a few eyebrows to be raised.
Have a look at the overall contrast performance of one, and we think you’ll agree that this is really not a crazy remark. The PS-64F8500′s best black level, which we measured from a nearly-black screen at 0.006 cd/m2, is neck and neck with this year’s Panasonics. The F8500 dims to near-black if an entirely black screen is input; we defeated this behaviour by keeping a small patch on screen (far away from the measurement area). Just for the record, we achieved these results by using the [Black Optimiser] feature. Setting this to “Dark Room” results in the 0.006 cd/m2 black level. By default, it’s at 0.018 cd/m2, which is still extremely good, but the extra depth of the “Dark Room” setting will be visible and appreciable in… well, a dark room. The menu blurb for this control promises that it will “get deeper blacks and magnify the contrast of low gradation by using PDP waveform and signal compensation”.
This control governs the use of Interlaced 30hz Reset Pulses in the panel driving algorithm. We will need to clarify this with Samsung’s PDP engineers, but our understanding is that this technique allows for very dark areas of the picture to be refreshed every second line, which in turn allows for considerably deeper blacks, and a hardly noticeable line pattern running through these areas. That’s an excellent trade-off, in our view.
If you press your nose up to the panel and look at it very carefully with a dark screen in a dark room, you’ll be able to see very small darker lines appearing to scroll up the screen at a fast rate.That’s hardly worth mentioning, but it’s interesting because we typically see this same effect on Panasonic plasma TVs (and from our recollection, Pioneer’s Kuro plasmas used it first). In fact, in 2012, we saw it on Panasonic plasmas, but only on the picture modes that prioritised contrast performance over gradation quality. “Ah-ha!” we thought, “is this a feature which reduces gradation in exchange for better contrast performance?” – apparently not. We had a look at just-above-black content on the PS64F8500 with and without the [Black Optimiser] mode on the “Dark Room” setting, and could see no difference in the amount of panel-generated dithering in the image, suggesting that the gradation is the same in both cases. Therefore, we left this feature on at all times, because we could see no reason not to.
It’s very interesting that Samsung felt the need to make this adjustable with a menu control: we searched high and low for this control causing other side-effects in the image, bombarding the 64-inch F8500 with test patterns and real-world content alike… and couldn’t find any significant downsides to turning it on. Perhaps they simply did so to draw attention to the improvement in black level.
A slightly less mundane difference relates to flicker. With the “Dark Room” mode turned on, we occasionally saw some very, very, very gentle flicker in some shades (10-20% grey windows, for example). This was incredibly mild to begin with, but disappeared when the feature was turned off. That is perhaps why control has been given over it. In any case, 99.9% of viewers will notice the richer contrast performance of the “Dark Room” mode more than the barely noticeable flicker, which is why we recommend this setting. The choice is down to the user.
As for our “OLED-like” claim, much of that is ultimately delivered by the PS64F8500′s peak white output. Black level is an important aspect of contrast performance, but it’s only one part. With [Cell Light] set to its peak position of “20″ and [Contrast] set to a level which did not discolour whites or discard peak white details, the PS64F8500 produced 166 cd/m2 on a white test window. During the ANSI checkerboard test, the figure was basically the same, at 163 cd/m2. That is a gigantic amount of light output for a screen this size.
By the way, the “Normal” mode produces a brighter-still picture than “Movie”, with ANSI white coming in at a dazzling 197 cd/m2 (blacks stay the same). This mode denies you access to the 10p White Balance control, but we found the PS64F8500′s greyscale quality (after calibration) to be totally sufficient with only 2-point adjustments made, so this is no loss. The “Custom” [Colour Space] is shared between modes on the same input, however. In any case, we just stuck with the “Movie” mode since it was more than bright enough already. In fact, given that we normally adjust HDTVs to peak white output of 120 cd/m2, the Samsung PS64F8500 marked the first time in a while where we had to reduce a plasma TV’s luminance controls to attain this. That’s just for our own testing, though – we recommend home users set the television up to a level that’s comfortable for them.
Samsung offers two controls to adjust peak white output: [Cell Light] and [Contrast]. The two produce a very similar result, although [Contrast] operates at the video processing level. Therefore, during calibration, [Contrast] should first be reduced (we only had to do it by a few clicks) so that near-white details are not crushed our or discoloured. From there, [Cell Light] can be adjusted to reduce screen light output, if necessary.
There has been some discussion as to which control is best used to reduce light output: for example, is it best to ignore [Cell Light], leaving it at full and reduce [Contrast] if a less bright picture is necessary? Or leave [Contrast] set and reduce [Cell Light]? The latter is the best way, as far as we can tell. Examine a gradient ramp and try reducing both controls and you’ll see that, as you’d expect, adjusting the [Contrast] control creates a small amount of banding due to the fact that this is a digital video processing adjustment (the same, or worse, would happen on any other brand’s HDTV, by the way) whereas the [Cell Light] control appears to be a more direct control over the panel driving, once the signal is out of the hands of the main video processing steps. Samsung’s video processing operates at a high bit depth (higher than the 8-bit sources available to consumers) so the banding is minimal, but it’s still best to avoid shifting levels around at all.
So, scientific testing reveals that Samsung has made yet another huge improvement to both ends of the contrast performance spectrum on the PS64F8500. It has astonishingly deep blacks, and whites that are insanely bright for a plasma display of this screen size. It’s a serious achievement, and it means that when both ends of the contrast spectrum are taken into account, Samsung is in first place ahead of Panasonic.
Like basically every other aspect of its performance, the PS64F8500′s motion rendering is of an extremely high standard. Like previous Samsung TVs, it resolves around 1080 lines on the FPD Benchmark scrolling test. Fast-moving areas are coated with a little dither noise, more than Panasonic’s plasmas, but not enough to be problematic (and much, much less than the constant dither of the legendary Pioneer Kuros). We’d bet money that significantly better motion rendering than this is really going to take a new display technology.
As always, 50hz content, which is output by the panel at 100hz to avoid flicker, has a few more false contouring artefacts during motion than the 60hz output mode. The 50hz reproduction is a little better than Panasonic’s, because while both exhibit extra contouring, the false contours on the Samsung F8500 don’t appear with any false colour effects (although that’s not a major issue with Panasonic displays). In any case, we still prefer this over LCD motion.
All Plasma televisions are affected by image retention to lesser or greater extents, with some of last year’s larger-sized Samsung panels being astonishingly resilient to this mildly irritating phenomenon (replace “mildly irritating” with “quite terrifying” for first-time plasma owners, who often mistake temporary retention for the dreaded “burn-in”, which it is not). The PS64F8500 showed a little bit of retention at times, which is more than last year’s biggest E6500 and E8000 plasmas did. However, it’s a rare and not very annoying occurrence all the same.
Samsung plasma TVs are unique when it comes to 3D because, relative to the competition (which means Panasonic), they scan each of the screen refreshing steps which make up one full 3D frame at full vertical resolution (1080 lines), whereas their Japanese rival has instead chosen to reduce the resolution of intermediate steps so that better gradation steps with less static contouring can be achieved in the third dimension.
We do prefer Samsung’s method, because, as highly attentive viewers, we feel that we notice the shortcomings of the alternative (some jaggedness visible in moving diagonal areas of detailed extra-dimensional images) more. And frankly, we don’t feel that the gradation or black level quality in the 3-D mode suffer as a result (these are apparently Panasonic’s reasons for using their alternative not-quite-Full-HD-3D method). Where Panasonic do have the lead in 3D is with greyscale tracking and colour accuracy, both of which are harder to get consistent on Samsung’s 3D plasmas. We feel that is a more subtle issue than Panasonic’s resolution limitation, though.
Especially after calibration, the PS64F8500′s tri-dimensional images were great, being fairly bright (compared to the plasma competition), full-res, and naturally coloured enough to keep us happy. Prior to calibration there was a more obvious red tint, but as we always point out, almost no viewers have ever seen a calibrated 3DTV so surely won’t notice. That doesn’t make it any less of an inaccuracy, though.
The PS64F8500 can’t output all types of 3-dimensional content without judder, though. The troublesome European 50hz standard outputs with some very minor motion stutter, but we doubt anyone will find it a problem. Arguably the most important signal type, the 24p output from 3D Blu-ray, is buttery smooth, and 60hz content is too.
Samsung’s handling of standard-def content is a cut above what anyone else is doing. Their edge-adaptive scaling process draws interpolated pixel data in a way which causes overcompressed, low-res SD TV broadcasts to look better than most people would think possible. This is hugely beneficial to synthetic content like TV animation. It keeps compression artefacts like mosquito noise to a minimum due to the fact that it does not place too much gain on high frequencies (which are rare in broadcast standard-definition television content anyway due to the pre-filtering done by broadcasters to produce “adequate” picture quality at lower and lower bit rates).
What’s more, the quality of the [MPEG Noise Reduction] feature is excellent. It can’t work miracles of course, but in the aforementioned animated content, it can do an incredible job of reducing mosquito noise without causing the “watercolour painting” effect which appears with more basic implementations of spatial image processing (there’s clearly some intelligent smoothing included as part of the bargain). Compare it to a competing HDTV with content like BBC Three‘s broadcasts of basic-looking TV animated shows such as Family Guy, and you’ll be able to see the difference. (While we’re on the subject, we’re unsure how the Beeb can possibly be getting such bad video encoding out of such simple and digitally-derived near-static content. On-the-fly encoding, ultra-low bit rates, and old encoders with poor motion estimation are our best attempts at guessing, but Samsung’s video processor makes the absolute most out of a poor quality source).
Also, the [Digital Clean View] feature (a temporal noise reduction control which averages out noise by analysing multiple frames in sequence) is beneficial for a lot of SD content delivered over the air. For high quality sources we prefer to leave this off so that fine textures and film grain aren’t removed by the television (Samsung previously didn’t give European users total control over this feature, but that’s not a problem this year), but when it comes to digital SDTV broadcasts, much of the damage has already been done by bargain basement bitrates and on-the-fly compression, so clearing away the rubble is hardly a travesty in that case.
The PS-64F8500 also correctly detects film-to-PAL video transfers to avoid those looking jagged, and smooths diagonal edges very effectively during the deinterlacing process of video content. In short, its SD to HD upconversion performance is top-notch.
Given how well the Samsung PS64F8500 has done in our benchmark tests for greyscale, colour, gamma, motion and contrast quality, you probably won’t be too surprised to hear that the picture quality with HD content is outstanding. After all, this is just the visual confirmation of the tests already done (of course, test patterns don’t always test every aspect of performance).
We’ve heard some online discussion where it’s claimed that the PS64F8500 has a “sharper” image than other plasma televisions. Given that basically every recent 1080p plasma display panel has been able to resolve at least full static detail from a 1920×1080 source (let’s ignore plasma-centric issues like gradation and dithering for a second), we’re not sure what the basis of these is, but we’d imagine that it has a lot to do with the F8500′s superior contrast performance, which could be said to make images appear perceptibly sharper.
In fact, Samsung’s plasmas produce minutely cleaner frequency response than Panasonic’s, since the Japanese manufacturer is still applying a bit of (essentially invisible) gain to high frequencies. Short of observing tiny differences in the contrast of small textures, the only way to spot this is to scrutinise test charts, so to be frank, it’s barely relevant 99% of the time – still, thumbs up to Samsung for providing genuine untampered images in this regard. You’ll never notice the difference, but the quality of both of these TV brands’ products is so outstanding that this is the sort of pixel-peeping we’re ultimately led to.
For the first time in the European market this year, Samsung listened to our pleas and made the noise reduction filtering optional. That means that the full filmic texture of high quality film transfers on Blu-ray Disc comes through unscathed, with full detail reaching the screen, and no small details, such as fine fabric weave and actors’ stubble, for example, are blurred out by any averaging processes. It would have been heartbreaking to say the least if Samsung’s flagship plasma screen had been saddled with this unnecessary video processing, but happily, this isn’t a problem. On the other hand, if you’re watching content on TV – where the high compression has taken its toll and created noise-like patterns (it’s not “noise” in the traditional sense of the word, which is why we say “noise-like”), then you can enable the noise reduction features if you like. This level of configuration will please everyone.
We could still find two small quirks with the PS64F8500, but they didn’t greatly impact our enjoyment of the otherwise outstanding picture quality. The first is what’s been termed as “brightness pops” by users, which is where the light output from the display will appear to quickly change during very bright moving scenes. We didn’t really notice this much in viewing and weren’t hugely bothered by it. Our best guess is that this is caused by Samsung’s implementation of ABL (Automatic Brightness Limiting), which we’re guessing is too sensitive to small fluctuations in brightness. A real world example is a camera pan down from a bright sky, revealing a more shadowed street-level view. The large change in brightness causes the 64in F8500 to display a slight flicker as the overall brightness level of the image changes.
The other was an occasional motion hiccup after some scene cuts. The easiest way to see this is to pause your disc player and then resume playback; you’ll be able to see a small “hesitation” after resuming playback. That on its own isn’t a problem of course, but it’s an easy way to demonstrate that the same thing can happen after scene changes. When we ran our motion interpolation detection test on the PS64F8500, we could see that when these small and infrequent “hiccups” occurred, the plasma was actually performing motion interpolation for one frame after the stutter (we needed our own test sequence to see this, the one frame of interpolation itself will not be visible in content; the small stutter will). Fortunately, it only appears very rarely and only during scenes that are more sedate anyway, so don’t lose your head over it.
Like many current Samsung HDTVs, the Samsung PS64F8500 has a “Game Mode” that’s best avoided because, while it cuts input lag, it doesn’t do so to a sufficient extent to give a really satisfying gaming experience.
Fortunately, selecting “PC” as the input label for the HDMI input to which your games console (or PC) is connected cuts input lag down to a satisfying level – the semi-hidden PC mode is a better game mode than the “Game Mode” is. Our Leo Bodnar lag tester reported the 64F8500′s fastest mode as lagging by 64ms, which is a decent, but not class-leading level. Our old CRT+camera measurement method resulted in a reading of 38ms, while we’re running both measurement methods.
Subjectively, we were mostly satisfied with the performance, although very fast, frenzied games revealed a little extra sluggishness compared to Panasonic plasma TVs (which are the PS64F8500′s nearest competition when it comes to fast, high quality displays).
The Samsung PS64F8500 is yet another extremely impressive plasma television from the Korean manufacturer, representing the boldest (and forgive us for saying it, but brightest) move yet from the company when it comes to plasma. It’s without a doubt the best flat-screen TV they’ve ever produced, and it’s a very strong rival to Panasonic’s own gas-and-phosphor-powered Viera HDTVs. Relative to what the Japanese brand is doing, the F8500 offers much of the same quality – and also some strengths of its own – for a good amount less. In the UK, the PS64F8500 has very little competition, given that the only comparably-sized panel being brought to these shores is the Panasonic TX-P65VT65B, which is some £600 more expensive. That move could mean that Samsung dominate huge-screen plasma sales in the United Kingdom (which admittedly is not likely to be a gigantic market). However, for some users, the cost savings are dented slightly when you remember that calibration is more necessary on the PS64F8500 due to its less impressive out-of-the-box greyscale tracking (although this varies from unit to unit, and we’d always recommend getting it done regardless).
On the whole, we were very happy indeed with the PS-64F8500′s performance. It produces outstanding picture quality with extreme contrast performance (deep blacks and very bright whites) commonly only seen on prototype OLED TVs, which will have astronomical price tags when they finally become available at this screen size (hell, given the constantly missed shipping dates for OLED panels, maybe we should be saying “IF they become available at this screen size”). Its greyscale, gamma and colour accuracy are all first-rate, and its handling of SD content is the industry’s best – and it’s here now.
It isn’t entirely free of quirks, however, and while those mean we can’t technically label the PS64F8500 a “reference level” product, please do keep in mind that it’s only a hair’s breadth away. We have a hard time imagining the few small issues we found being deal-breakers for too many people, especially when you consider the image quality and value for money on offer. The improvements which Samsung have been making to their plasmas in recent years are astonishing, and that’s before you consider the rate the improvements have been coming at. In fact, by promoting largely the bright whites, but being quieter about the incredibly deep blacks, Samsung have underpromised and overdelivered with this display. We strongly recommend you check the PS64F8500 out if you’re looking for a top-grade, large-sized HDTV.
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