Thursday, November 1, 2018

LG B8 vs C8 Review (OLED65B8PUA vs OLED65C8PUA; OLED55B8PUA vs OLED55C8PUA)

The main LG B8 vs C8 difference is their video processing capability. Due to a different image processor being used on LG B8 vs C8, the number of steps in the MPEG Noise Reduction process is different, and so are the depth and sharpness enhancer techniques on the LG B8 vs C8. That being said, the impact of these features on the picture quality is limited (and they can be discarded altogether when watching high quality sources). There is one exception, though, and it concerns content with in-source posterization artifacts in which case the LG C8, due to the second pass of decontouring filters, is more effective in providing smooth gradation than the LG B8 which relies on a single-pass banding removal. Out-of-the-box color accuracy is also distinct on the LG B8 vs C8 (due to the different number of color data points in the internal 3D cube look-up tables the two OLED TVs have), and so are HFR (High Frame Rate) capabilities (but only when the 4K signal includes HDR). Differences on the LG B8 vs C8 not related to video processing are design of the table top stand and screen sizes they can be found in. There is some distinction in the HDR peak brightness on the LG B8 vs C8 in low-APL (Average Picture Level) scenes during which specular highlights can be rendered slightly brighter by the LG C8 vs B8.

Processor Alpha 7 Alpha 9
Up to 35% increase in CPU & GPU performance on Alpha 9 in comparison to Alpha 7. Memory performance is improved by up to 50% on TVs with Alpha 9 vs Alpha 7. The CPU and GPU improvements are important for image processing, real-time analysis of video signal in particular, and determine how complex picture enhancements the B8 and C8 are able to perform.
B8 C8
Firmware 04.10.06 04.10.05
The firmware updates for LG B8 are released at the same time as those for the LG SK9500, SK9000, SK8070, SK8000 LCD TVs (since they have the same Alpha 7 processor). The latest version is 04.10.06, and was released on September 14, 2018. When it comes to the LG C8, though, it has a different processor (Alpha 9), so the timing is different. For example, the latest version is 04.10.05, and it was released on October 5, 2018. The firmware updates for LG C8 are released alongside those for LG W8, E8 OLED TVs since they also have the Alpha 9 processor. Despite the version number and timing differences, the latest firmware for either the LG C8 or B8 adds the same functionality (e.g. Google Assistant is available in more countries), reduces the time cursor stays on screen when the Magic remote is not used, and provides fixes for various bugs.
B8 C8
MPEG Noise Reduction 2-step 4-step
This process comprises noise reduction and smooth gradation filters, with each filter being applied only once in the B8 (so the entire process is dual-step), and twice in the C8 (hence the quad-step process). Useful mostly for poorly compressed sources that may benefit from the simultaneous application of the noise reduction and smooth gradation filters. Generally not needed for high quality content unless there are some banding artifacts.
B8 C8
Smooth Gradation 1-pass 2-pass
Part of the MPEG Noise Reduction process. The C8 is more effective in removing in-source posterization artifacts (caused by quantization errors when the bit rate is too low) than the B8 but the loss of fine detail is also more pronounced in comparison to the B8 (especially if the content is high quality) since not only the smooth gradation is two-pass but so is the noise reduction on the C8.
B8 C8
Depth Enhancer Edge-based Object-based
This technique identifies either the main object in the frame (in C8), or its edges (in B8) for the purpose of further processing intended to make it more distinct against the background, eventually leading to more dimensional image. That being said, the infinite contrast ratio on both LG OLED TVs by itself is enough for images to be displayed with an exceptional depth, without the help of any additional enhancements, meaning there isn't any significant variation in the picture depth on C8 vs B8.
B8 C8
Sharpness Enhancer Yes Yes: Frequency-based
The LG C8 is able to analyze edges and textures separately and process them accordingly so that not only the sharpness of the edges is boosted, but so are fine details in textures. However, it doesn’t lead to any profound difference in the picture quality on LG C8 vs B8 either.
B8 C8
True Color Accuracy Standard Pro
Indicates the size of 3D Cube LUTs (Look-up Tables). The LG C8's advantage over B8 in terms of color accuracy is within the limitations of the factory calibration (which is not comprehensive). Nevertheless, out of the box color reproduction is generally more accurate on C8 vs B8 but both TVs can be calibrated to a reference level of picture quality, either manually or automatically using the CalMAN software by SpectraCal (sold separately). This software has a direct access to the C8 and B8's internal 3D an 1D look-up tables (the latter are identical on either B8 or C8 since they contain 1024 reference data points for calibrating grayscale and gamma). To perform an auto calibration of the TV, however, you'll also need a colorimeter and pattern generator (sold separately from the TV).
B8 C8
3D LUT Size 17x17x17 33x33x33
The C8 can store ~7.3x more color coordinates than LG B8 in its 3D LUTs. Specifically, the number is 4,913 and 35,937 color data points (on the LG B8 vs C8, respectively). Considering these data points are used not only for direct color corrections but also as a reference when the TV calculates the position of any of the 1.07 billion colors on either LG B8 or C8 that cannot be directly looked up, the LG C8 has to perform fewer color interpolations which makes it less likely for any errors in color calculations to occur in comparison to the LG B8.
B8 C8
HFR (USB/Streaming) 4K HFR 4K HFR + HDR
Until 4K content that is simultaneously HFR (High Frame Rate) and HDR (High Dynamic Range) is available for streaming via some of the TV's internal apps, the C8 doesn't have any practical advantage over the B8 in terms HFR since both are equipped with a HEVC decoder conforming to the Main10 profile at Level 5.2, meaning that they can decode HEVC files up to 3840x2160 at 120 fps (maximum bitrate 60Mbps) via USB. They also have a VP9 decoder but it is limited to 60fps in 4K resolution. When HDMI connection is used, the limit is 1080p @ 120fps on either LG C8 or B8 due to the lack of HDMI 2.1 ports (the bandwidth of their HDMI 2.0 ports in not sufficient for 4K@120fps).
B8 C8
Table top stand Trapezium Streamlined Alpine
Stand Width (Max) ~25.8" (65.5cm) ~40.1" (101.8cm); 77-inch: ~46.8" (118.9cm)
The C8's stand is ~14.3" wider than the B8's. Due to the concave sides of the alpine stand, the top half is wider than the bottom half so even though the maximum width of the stand in the 55-inch and 65-inch class LG C8 OLED TVs is approximately 40.1 inches, they can still fit on a table or TV cabinet that measures at least 35.5 inches in length. The 77-inch C8 class model requires wider surface, though. The alpine form factor of the stand and the cutout under the down-firing speakers serve the purpose of reflecting sound towards the front of the TV, thus providing a slight advantage in terms of clarity of voices and dialogues on LG C8 vs B8 which has a different stand without a cutout. Nevertheless, you can further optimize the sound on either LG B8 or C8 by using the Sound Tuning feature that relies on the built-in microphone in the Magic Remote to determine where the TV is placed, and provide some basic form of acoustic room correction. One advantage of the trapezium stand is that it's less wide and heavy than the alpine stand, meaning the LG B8 should fit on a wider variety of furniture.

Other differences
HDR Brightness
It needs to said that there is some variation between C8 and B8 when the HDR scene has low-APL (Average Picture Level) which means that most of it is dark. Specifically, small specular highlights that are approximately 70cd/m2 to 90cd/m2 brighter can be displayed by the LG C8 in comparison to B8. However, it is not very noticeable and doesn't have a significant impact on the picture quality. If you find the overall HDR image to be too dim, there are tools on either LG B8 or C8 to correct that. Specifically, the PQ EOTF tracking can be adjusted with the Dynamic Contrast setting found under Advanced Controls in order to brighten the scene, for example, or use the Dynamic Tone Mapping with HDR10 or HLG content in order to prevent any unnecessary compression of the dynamic range during scenes without highlights. The reason why you need to adjust the PQ EOTF tracking instead of simply using OLED Light setting is because the PQ (Perceptual Quantizer) EOTF (Electro-optical transfer function) used with HDR10 and Dolby Vision content is an absolute transfer function rather than being relative like the BT.1886 gamma used with SDR content, which necessitates each specific bit level to be mapped to a predefined luminance level and for that reason OLED Light is already maxed.

Identical Features
SDR Brightness & ABL (Auto Brightness Limiter)
The ABL adjusts luminance based on the APL (Average Picture Level). Nevertheless, the luminance level is constant (at ~400cd/m2) up until 70% APL, meaning that low-to-mid APL content (i.e. most movies and TV series) is not affected by the ABL (Auto Brightness Limiter). In other words, only during high-APL scenes (i.e. predominantly bright) you can observe the brightness getting progressively lower as the APL increases. In order to avoid brightness fluctuations (in high-APL scenes) altogether, you need to calibrate your TV to less than 150cd/m2 which is the ABL activation threshold. Given that SDR content is usually mastered for a peak white of 100cd/m2, there is still some headroom on either C8 or B8 for making high-APL content brighter.

The DCI-P3 color gamut coverage in mid-tones is approximately 99% on either LG B8 or C8. This color gamut is used for HDR content (within Rec.2020 container), and the two LG OLED TV's near full coverage of the DCI-P3 gamut allows you to see colors as the content creators intended, at least in shadows and mid-tones. The reason why they are able to show fully saturated colors in the shadows is their perfect black level which ensures that when some of the primary colors are mixed, there is no contamination with dark gray which is spectrally broad (and leads to a decrease in the color purity). When it comes to saturating bright colors, however, it should be said that neither LG B8 nor C8 can optimally saturate colors in HDR highlights. The reason being is the four-subpixel layout their OLED panels use, and the spectrally broad white light mixing with any of the three primary colors in particular. This can be observed only in some of the brightest HDR highlights, though, and doesn't affect SDR content or shadows and mid-tones in HDR content which are properly saturated. SDR content uses Rec.709 color gamut which is smaller than the DCI-P3, so either the LG B8 or C8 can fully cover it. Thanks to the 10-bit panel, they can render 1.07 billion color shades which naturally provides an image without banding artifacts (unless the posterisation is in the source content).

Black Level & Near-black gradation
Since OLED is a self-emissive technology, the light control on the LG B8 vs C8 is done on a pixel level. The ability to turn individual pixels off allows either the LG B8 or C8 to have a perfect black level, and consecutively: an infinite intra-image contrast ratio. Furthermore, they are exempt from any halos around bright objects against a dark background, or other backlight-related issues such as flashlighting from the corners, for example. Furthermore, they don't exhibit any dirty screen effect, either. One area that has been slightly problematic for OLED TVs is the transition form black to dark gray. In order to avoid near-black gradation issues, 1D LUTs (Look-up Tables) that are non-linear are utilized on either LG B8 or C8 so that more bits can be allocated for the lower end of the grayscale. As a result, dark tones are rendered relatively smoothly by both the LG OLED TVs.

Viewing Angles & Reflections
Having the light source almost immediately to the front glass, OLED TVs are able to maintain the image quality largely intact when viewed from the sides leading to wide viewing angles on either LG B8 or C8. There is no raise in the black level during off-axis viewing or any significant drop in brightness. It should be said, though, that some color shift can be observed but it occurs only past 45 degrees off-center. The anti-reflective filter is identical, so there is no difference on the LG C8 vs B8 when it comes to on-screen reflections since both TVs are able to effectively minimize them.

The native refresh rate of the panel is 120Hz on either LG B8 or C8. This allows the motion compensated frame interpolation to be used even with 60 fps content. You can adjust the level of motion smoothness with the De-Blur slider which is part of the User setting for the TruMotion technology. There is also another option called De-Judder which is useful for reducing stutter with low frame rate content such as 24 fps movies. The reason stutter occurs is the nearly instantaneous pixel response time on either LG B8 or C8, meaning they are able to render the frame for less than 1ms but need to keep displaying it for 8.3ms due to the sample-and-hold method they are based on. Given that each frame of 24 fps content is repeated 5 times on a 120Hz TV, this adds up to an approximately 40ms during which the same frame is being displayed followed immediately by the next one without any motion blur to smoothen the transition, hence the stutter. However, this is mostly limited to low frame rate content whereas with 60 fps content, for example, the instantaneous pixel response time ensures that there are no dark trails or ghost afterimages following fast moving objects.

Black Frame Insertion
There is no difference on LG B8 vs C8 in terms of black frame insertion since both have a setting called Motion Pro for activating it. Due to the nature of this feature, though, it's possible to exhibit flickering of the screen but this is exactly what allows the continuous light output to be interrupted, so that a moving object doesn't appear blurred across the retina due to the fact that each frame is static for 8.3ms whereas the eyes are constantly moving when they follow motion.

Input Lag
The input lag is ~21ms on either LG B8 or C8 regardless if the source signal is 4K or 1080p. However, they are not able to maintain their low input lag in the event frame interpolation is used. Variable Refresh Rate is not supported by either LG C8 or B8, so they are not compatible with the FreeSync technology, for example.

Dynamic Tone Mapping in Game mode
If you're playing HDR games and the image is too dark, they have Dynamic Tone Mapping capability that can brighten shadows and mid-tones when there are no highlights. Additionally, more details can be resolved in spectral highligths but mid-tones and shadows need to compressed. In order to improve motion clarity, the Black Frame Insertion can be turned on while playing games but this may create visible flickering and reduce image brightness.

There is no difference in the speaker configuration on the LG B8 vs C8 which is 2.2 channel on both, or the total audio power output since both TVs deliver 40 Watts of amplification (20 Watts are allocated for the Woofers). As a result, the frequency response on the LG B8 vs C8 is in the same ballpark, and the bass is relatively deep on both TVs. They have a Dolby Atmos decoder so that such soundtracks can be played back directly by the TV's on-board sound system. That being said, there are no height speakers on the LG B8 or C8, meaning that they have to reproduce 3-dimensional sound only using their stereo speakers which is less than ideal. Alternatively, you can bitstream Atmos tracks to a compatible receiver or a soundbar via HDMI ARC as long as they're Dolby Digital Plus encoded rather than Dolby TrueHD which is lossless format, and exceeds the bandwidth capacity of the HDMI ARC.

There are 4 HDMI Inputs (version 2.0) on either LG B8 or C8 but no HDMI 2.1 ports. HDCP 2.2 is supported on all 4 HDMI inputs so there are no restrictions in terms of which port to use for connecting an Ultra HD Blu-ray player, for example. Three of the HDMI inputs are side-facing while one is rear-facing. There is no difference on LG B8 vs C8 in terms of USB inputs since both TVs have 3 of them but they all are version 2.0, meaning there isn't a single USB 3.0 port on any of the two OLED TVs. Two of the USB inputs are side-facing whereas the remaining USB input, in addition to an Ethernet port, an optical digital audio out, a RF input, a RS232C (Mini Jack), and a composite input (with the included adapter) are all rear-facing on either the LG B8 or C8. There is no DisplayPort. In terms of wireless connectivity, they have a built-in Wi-Fi (802.11ac) and Bluetooth 4.2.

Smart TV
The smart TV platform is webOS 4.0 on either the LG B8 or C8. The bottom half of the home screen is where you can find the launcher bar. The input you're currently using or the application you've opened is shown at the left, whereas the rest of the launcher bar is taken by icons for different apps. These can be rearranged or deleted. By long-pressing the home button, a list of recently used apps is invoked. In addition to connecting devices such as a set-top box, blu-ray player, sound bar, or game console to you TV, the webOS allows you to either share the screen of your smartphone, or play content from it on your TV. The screen sharing is done wirelessly but you phone has to support Miracast. To cast content from your Android or iOS device to your TV, or use it as a remote control, you'll have to install the LG TV Plus app on your mobile device. Furthermore, both devices have to be on the same wireless network in order for this functionality to work. Alternatively, you can use Wi-Fi direct, provided your mobile device supports it. The LG AI ThinQ system allows the two OLED TVs to perform an intelligent voice interpretation of commands you issue using the built-in microphone in the Magic remote, in addition to giving them the ability to improve over time by utilizing machine learning techniques. Furthermore, the Google Assistant is built-in on either the LG B8 or C8 thanks to which they can control other connected smart devices, thus acting as an IoT (Internet-of-Things) hub.

Smart speakers compatibility
They both are compatible with Amazon Alexa devices (sold separately), and Google Home devices (sold separately). The Amazon Alexa compatibility is dependent on a firmware update for the TV which has already been released. Either the LG B8 or C8 can be voice-controlled via two Alexa skills (the selection is done in the LG SmartThinQ app which needs to be installed on your mobile phone). The “LG SmartThinQ – Smart Home” skill allows Alexa to directly control your TV whereas the “LG SmartThinQ” is a custom skill type if you'd like Alexa to redirect your voice commands to the LG SmartThinQ system so that you can issue more complex commands.

There is no difference on LG B8 vs C8 in terms of the included remote. They both have the same Magic remote which has an accelerometer, meaning that it can detect motion and act identically to a computer mouse. The point-and-click functionality makes navigation very easy. The number buttons on the Magic remote can be assigned to an application or input for a quick access. Up to 9 keys can be used for that purpose, and you can manage the Quick Access function by long-pressing the "0" key. There are dedicated buttons for Amazon Video and Netflix, so you don't need to assign these two services to a number button.

LG calls the design used for either LG C8 or B8 Cinema Screen. The top half of the TV is extremely thin because all inputs and electronic components are located near the bottom of the back panel. Although this section protrudes a bit, the maximum depth of the two TVs (without the stand) doesn't exceed 1.8 inches in the 55-inch and 65-inch class. The 77-inch class LG C8 model, however, is slightly thicker since it measures 2.2 inches in depth. An identical color scheme is used for either the LG C8 or B8. The bezels are black (and very thin), meaning that they can completely disappear when watching your TV in a dark room. The section on the back panel where the electronics and inputs reside is dark gray whereas the top half of the back is light gray. The cable management consists of only a small removable cable holder. That being said, its central position, just above the stand, allows for cables to be routed exactly behind the stand (which is especially useful for the three side-facing HDMI inputs). As a result, when the TV is mounted on a table-top stand, the cables won't be visible from the front.

Pixel Refresher (OLED Panel Settings)
Mode Runs every Duration
Automatic 4 hours ~5 Minutes
Manual 2000 hours ~1 hour
The prevention and mitigation of image retention is identical on LG B8 vs C8. Both LG OLED TVs are configured to automatically run short compensation cycle after accumulating 4 hours of screen-on time in order to be able to measure the voltages supplied to different areas of the panel, and correct any irregularities thus maintaining optimal screen uniformity and clearing any temporary image retention. This process lasts several minutes, and is performed when the TV is turned off. After 2000 hours of use, you may be prompted to manually start the Pixel Refresher so that either the LG C8 or B8 can perform more comprehensive compensation cycle which is approximately an hour long. If, for example, you watch TV for about 5 1/2 hours every day, you will only have to use the Pixel Refresher once per year. The brightness level is automatically reduced by either LG B8 or C8 when a static image is left on display for some time. Given that the dimming is gradual, it's not very noticeable. Upon detecting a moving image, the brightness level is restored. It should be said that the screen dimming is different from the auto brightness limiter the purpose of which is to protect the panel and electronics from overheating, in addition to keeping power consumption within certain limits when the scene has high-APL (average picture level).


  1. Hi. I was reading the comparison between LG B8 and LG C8. In the HFR section. What is the maximum frame rate that the B8 can support if the signal is 4k (3840 x 2160) and HDR? What is the maximum for the C8?

    Essentially, I dont know the definition of what constitutes "HIGH" frame rate. I am aware that 24hz is typical in movies and films in general, and 50hz and 60hz is typical for broadcast television programing. My current guess is that HFR is anything above 60hz (the highest typical)...but perhaps a 4k HDR 60hz movie could be considered HFR because 60hz is above the typical 24hz on movies.

    Can the b8 do 4k hdr at 60hz?

    1. Hi,

      120fps (frames per second) is considered HFR (High Frame Rate).

      The LG C8 supports 4K HDR 120fps, albeit only via streaming and USB (and not via HDMI).

      The LG B8 supports either 4K 120fps or 4K HDR but not 4K HDR 120fps due to the less powerful Alpha 7 processor. However, the LG B8 is able to do 4K HDR at 60fps, even via HDMI.

      Hope that helps.

    2. So C8 or B8 for the PS4 Pro?

  2. @Anonymous

    Unfortunately, I don't know when HFR + HDR content might become mainstream. It needs to be said that HFR content (120fps) has limited application (mainly for some sports), though, so mainstream is quite relative, especially considering that movies and TV series in general don't require such high frame rates.

    If the 4K HFR HDR support is the only reason you're considering the C8 vs B8, then you should probably go with the B8.

  3. Can the two TVs take a full 120hz @ 1080p signal from a PC or does it take a 60hz signal and use software to build the extra frames? Might be a big deal to be able to play PC videogames on it at full 120fps.