Samsung Q8 Image Analysis Review
By Chris Heinonen on
For 2018, Samsung listened to what people said about their 2017 sets and has released some of their Q-Series lineup featuring full array local dimming backlights. The least expensive option with FALD, which provides the best image quality for LCD TVs, is the Q8F and we will look at how its image quality stacks up to the competition today.
Samsung Q8F SDR Calibration
For all our calibrations we use CalMAN software with a Murideo Six-G, i1Pro2, and Klein K-10A. With SDR we target the Rec.709 HDTV standard along with a BT.1886 gamma target. The Samsung supports auto-calibration from CalMAN, letting you get around needing to use the on-screen menus, but in our case using that also means a USB to RS232 Adapter, an RS232 null modem cable, and an RS232 to 3.5mm adapter to connect a laptop to the TV. Hopefully, they add IP support in the future.
The most accurate mode out of the box for us was Cinema, so that was our basis for calibration. Unlike every other TV we have tested this year, Samsung doesn’t let you disable local dimming on their TVs completely. This means the contrast ratios you’ll see here compared to other displays are unfair, and if you are bothered by local dimming there is no way around it. We used low for doing the measurements to try to avoid the impact, but there was no way to completely get around it.
The grayscale in the default Warm color setting has a distinct red push you can see, though the gamma tracks BT.1886 fairly well. Because of the significant red shift, the grayscale errors are 3.0 or larger from 40% and up, with them peaking at an error level over 8.2 at 100% white. This is the largest grayscale error we’ve seen on a display this year in the most accurate mode, as most companies are shipping displays that are more accurate than this now.
Colors also show noticeable error, with both saturations and luminances having significant numbers of measurements over a dE2000 level of 3.0 and the averages for saturations and color checker over 3.0, with luminances at 2.94. Gamut coverage is good at 97%, with some over-saturation in red but noticeable tint shifts in the secondary colors.
When calibrating the grayscale, my first inclination was to reduce the contrast and see if it was clipping the other colors. Reducing it down did improve the RGB balance, but it also adjusts the gamma and local dimming at the same time. This resulted in a grayscale error level that was even worse than before, so I left this at the default 45 setting.
You can also calibrate the Samsung using 100%, 75%, or 50% saturation points, but each has their downsides. 100% gets the gamut correct, while 50% and 75% resulted in red being over-saturated and outside of the gamut. But using 100% led to the error levels at 50% and 75% being higher than if you calibrated with either of those targets as well. In the end, I found the best results were from using the 50% target, which resulted in the overall lowest errors across the board.
Post-calibration, after using the manual controls and the DDC controls available, the grayscale is brought into line. The average dE2000 error has fallen by almost 3 points, and the largest single error reading is 1.16 and still invisible. The gamma is brought into line some more as well, and the results here after calibration are much improved. The overall gamma is slightly dark, but some of this is due to the local dimming that we cannot defeat so we can’t measure the gamma of the panel without it.
Colors also benefit, though there are still issues with luminances in yellow and red. Far fewer of the color checker points are now above 3.0, but there are still some there. Overall the Samsung Q8F highly improves from a calibration compared to the default settings, but it still isn’t as accurate as many of the other displays we tested this year in SDR mode. It especially is inaccurate out of the box in comparison, and calibration is considered far more essential on this than it is on other displays that you might look at.
Note that before doing an auto-calibration, you need to set the colorspace to Custom, as otherwise, CalMAN has an error. They’ll likely fix this problem (it did this for you in 2017 models), but for right now it’s worth keeping that in mind.
Samsung Q8F HDR Calibration
Testing in HDR mode, the EOTF was too bright until I adjusted the gamma down to make it track closer to the optimal level. Setting the gamma to -2 let me track the EOTF much more accurately than before, though it results in the image being slightly too dark. It still offers the lowest overall dEICtCp average for grayscale, which is my goal. Samsung has said that they feel consumers prefer a brighter HDR image, so they are doing that instead of following the EOTF accurately.
Before calibration, we see an RGB balance that shifts to red, and a large error in red when we look at 50% saturation. Since the Q8F also had a red push in SDR mode, it seems that Samsung is pushing red a bit this year, or this set just has an error there. Of course, once we add in luminance the error levels increase, with the grayscale being too bright at the end instead of stopping at 1000 nits. Color gamut coverage is good with 97-98% coverage of the DCI/P3 gamut and close to 80% of Rec2020. We also see over 1300 nits when using a 10% window, but we’ll come back to this in the next section when we talk about tone mapping.
Auto-calibration of HDR isn’t working yet with CalMAN for the Samsung Q8F, so everything here is done manually. We are able to fix the RGB balance so it is correct, and you can see in the charts without luminance for grayscale that the error levels are quite low. What we cannot fix is the EOTF, as it tracks incorrectly even after the gamma adjustment, and the error levels average 8.3 here. Since the Q8F can hit 1000 nits on a window pattern, it should be able to display 1000 nits HDR with essentially no errors if it tracks the EOTF correctly, but Samsung has chosen to go a different route. I’m not opposed to having it be brighter from 70% and up, but it doesn’t track below 70% that well either.
Colors show this more here, with the saturation sweeps showing even lower saturation levels have their luminance levels incorrect. Looking at the errors without luminance they’re OK, so the colors are accurate otherwise, but the content has luminance so I focus more on that data. I’ll discuss this more when I talk about tone mapping in the next section, as I think this is a choice Samsung has made this year with their displays and it isn’t a bad choice, but it’s a distinct choice.
We still see 1314 nits here, so the image (at least with test patterns) is quite bright, and gamut coverage is good. Color volume numbers are very good, as you can see in the chart below. Of course, there is no Dolby Vision HDR support here, and there is no HDR10+ content or test patterns to use for testing that yet. While the Samsung Q8F data for HDR looks good without including luminance, it has issues following the EOTF and won’t be as accurate as other TVs on the market.
Samsung Q8F Video Processing and Features
The biggest thing to talk about with the Samsung Q8F is the implementation of their local dimming for the full array backlight in the Q8F. Samsung has made a very distinct choice here to avoid blooming artifacts and to preserve highlight details that impact the performance of everything else. This has some positive benefits, which I think many people will like, but also some negative ones that come up.
Watching clips from the 4K Blu-ray of Batman vs. Superman, I compared the Q8F to the Sony Z9D and the Vizio P65-F1. On very bright highlights, they each offered very distinct takes. The Sony was easily the brightest but would clip very bright highlights as white and miss some fine details. The Vizio would try to maintain peak brightness but still keeping highlight details, though due to a lack of saturation the overall highlight was mostly white, while the Sony only had the clipped section as white and the rest has color. With the Q8F, it would keep the highlight color, and also maintain the detail in it. So at first glance, this looked better than the rest, offering both improved saturation and full details.
However, Samsung does this by reducing the peak brightness far more than the other displays. While they will track the EOTF correctly here, Samsung will reduce the light output of everything to maintain that detail that I saw. So while you might see a bright highlight that keeps its color, that highlight isn’t nearly as bright and vivid as it would be on a display from another company.
This behavior carries over when you look at scenes in outer space on Gravity. The other two displays keep the starfield completely visible on this SDR disc, while on the Q8F the stars are almost completely invisible. In attempting to not add blooming artifacts with the full array backlight, the Samsung is crushing details and they are not visible at all. This also causes it to have some shadow crushing in very dark areas, as it again tries to avoid haloing artifacts and reduces the backlight too much. When watching sports or brighter content you won’t see this, but you can notice it directly next to another display.
The local dimming also takes a bit of time to react on quick cuts. Watching The Equalizer on 4K Blu-ray, there is a shot early in the film that cuts to a room in his house, and you can see the room dim as it is cutting from a brighter scene to a dim room. It looks as if they are dimming the lights in the room after it switches, but it is just from the reaction time of the Q8F. Overall this behavior is the reason that while I think the 1300+ nits that the Q8F can produce is a great number, I don’t think you’ll almost ever see that in real life. Maybe a firmware update will improve this down the line, but currently, the backlight is so aggressive in preventing blooming that it has overall lower light output.
Possibly the best feature of the Q8F for video is the anti-reflective filter on the front of the screen. When compared to other LCD panels, the Q8F looks completely black when turned off while the others reflect far more light. Watching it in a living room with plenty of windows, the Q8F sucks up those ambient light reflections far more than other displays and works great in a room with lots of windows. While I sometimes have issues with too much light in here, especially from a skylight that is open, the Q8F never had a problem.
You can use black frame insertion on the Q8F, but I found it to introduce a noticeable flicker that made it impossible for me to leave on. Other displays this year have a much better BFI implementation that doesn’t show nearly the flicker or artifacts that you see here. However, game mode on the Q8F is ahead of the competition with support for auto low latency mode and variable refresh rate. You can also do frame interpolation that works in game mode and introduces very little lag. Know that if you enable freesync than auto low latency mode no longer works and you’ll have to be in game mode all the time.
Samsung Q8F Image Performance Conclusions
The Q8F is a mixed bag when it comes to image performance. It has some aggressive tone mapping that lets you maintain highlight details and saturation, but to do so it reduces the overall brightness and loses the benefits of producing 1300 nits. It also can crush shadow details and starfields which other displays handle just fine without excessive blooming. Perhaps Samsung needs more full array fields here, though the Q9F also has similar issues with far more local dimming zones. The inaccuracy of the image out of the box means that you are more likely going to want to pay for a calibration of the Q8F than some other displays out there.
The AR filter on the Q8F makes it a wonderful choice for a bright room, as it sucks up all those ambient light reflections more than any other display I’ve tested, and the game modes make it great for gaming. The Q8F is a good display for SDR after calibration, and with HDR you’ll see all the details in highlights, but it doesn’t follow the EOTF correctly or use its peak brightness to its full ability. It’s a good TV, other TVs can offer superior images for the same price, though not the AR filter and game mode improvements that Samsung has.