LG 55 B4 vs TCL A400 PRO

The HDR brightness performance of the LG B4 is impressive, even though it doesn't surpass 1000 nits. Its luminance stability is consistently strong across various scenarios, delivering a reliable viewing experience. The only instance where the TV shows slight weakness is in scenes with large areas of bright white, which has long been a challenge for OLED technology. However, perfect contrast, deep blacks, and excellent brightness ensure a fully immersive HDR experience. Furthermore, the TV’s remarkable 99% coverage of the DCI-P3 colour gamut enhances its colour vibrancy, making images appear rich and visually striking. This level of colour accuracy and brightness balance firmly places the LG B4 among the top choices for HDR content.

The TCL A400 Pro is a moderately bright TV. Its peak brightness reaches about 600 nits. That level already allows for a real HDR effect and in many movies it does produce a noticeably more attractive picture than SDR. However, it is not a level that overwhelms by brightness alone. The A400 Pro is not one of those TVs that "attack" the viewer with a powerful flash in every dramatic scene. The biggest limitation is visible with small bright elements on a dark background. Due to rather aggressive control of the dimming zones, the TV can significantly reduce their brightness — in extreme cases down to around 100 nits. That means small lights, sparks, stars, or single highlights can be much less visible than they should be. That said, this is not done without reason. The A400 Pro does this to keep blacks as deep as possible and to limit haloing around bright objects. It's a deliberate compromise: the TV more often chooses deeper blacks over maximally bright, point-like highlights. On one hand this is understandable, especially with a limited number of dimming zones, but on the other hand you should be aware that the HDR effect will not always be as strong as the peak brightness alone would suggest.

On the plus side, the colors are worth noting. The PFS LED filter used here, marketed by the manufacturer as QLED, produces suitably saturated colors. Our measurements showed about 94% coverage of the DCI-P3 gamut and about 74% of BT.2020, which is a solid result for this class.

The best factory preset offered by LG B4 is the "Filmmaker" mode, which we used throughout our testing. Straight out of the box, the TV delivered fairly accurate colour reproduction. However, the most significant issue in both SDR and HDR content was the white balance. In SDR, there was a noticeable red dominance, giving the image a distinct yellow tint, particularly evident in skin tones and whites. In HDR, this red hue persisted, but the lack of blue also introduced a greenish tint in certain scenes. Additionally, we observed some inconsistencies in grayscale and colour accuracy. Despite these shortcomings, the overall picture quality was still solid for most viewing scenarios.

As standard, we carried out color measurements in the best-calibrated mode, Filmmaker Mode, the one that is supposed to be closest to the creators’ intent. The A400 Pro, of course, also offers other picture modes, but in practice they suffer from much larger color errors and alter the image character more strongly. We won’t go into those modes in detail in this part of the test. So how does the factory color reproduction perform? In short: really very well. In fact, looking at our measurement results, it’s excellent. Both the white balance and the luminance response were set surprisingly precisely. The errors were so small that during testing we genuinely rubbed our eyes in disbelief. Such good out-of-the-box settings don’t happen often, even in TVs operating in Filmmaker Mode. All the more reason to praise TCL, because the A400 Pro right out of the box can produce an image very close to how the source material should look. The results were so good that you could easily think someone had already paid extra attention to that unit and tried to calibrate it.

Our nitpicking really comes down to just one thing. In SDR content the image was slightly brighter than the reference for a dark room, because the factory gamma was set closer to 2.3 than to 2.4. It’s not a big error and most viewers probably won’t even notice it.

However, it should be noted that we’re talking about our specific review sample. With factory colors there can always be some variation between units, production batches, or screen sizes. So we don’t assume that every A400 Pro will look identical straight out of the box.

LG B4 has long been known for offering advanced calibration tools, and it remains one of the few manufacturers that allows such in-depth image adjustments. Thanks to these tools, we calibrated the device to an exceptional standard. The result was incredibly low deltaE errors, considered at a reference level. Both SDR and HDR content now display exactly as the filmmaker intended. This level of precision is one of the reasons LG TVs are frequently used as preview monitors in graphic design and post-production studios.

Despite its excellent factory tuning, we couldn't resist checking how the TCL A400 Pro would respond to a professional calibration. Since the starting point was so good, we were even more curious whether we could squeeze even more out of this TV. And here we have to boast: we managed to bring our unit to absurdly low color errors. Results below 1 are something you don't see every day, even on very good TVs. Such results are more often associated with professional reference monitors than with a lifestyle TV for the living room. In terms of white balance and color reproduction, the A400 Pro after calibration simply performed outstandingly. The only thing we can pick at after a deeper analysis concerns the brightness behavior. The TV can manipulate luminance levels depending on the content being displayed, and quite often the image is a bit darker than it should be according to the standard. This most likely stems from the way the Mini-LED backlight and local dimming algorithms work in this model. However, that doesn't spoil the overall impression, because in terms of color precision alone the A400 Pro after calibration reached a level we really didn't expect.

In this section, we will revisit the smooth transition function while also examining how the TV handles lower-quality content. As we’ve found, the setting responsible for smooth gradation is generally effective, though it does have its drawbacks. While the function works well in SDR content, it becomes less useful in HDR content. Even at the lowest setting, it can blur important details, so we advise against using it in such cases.

The image scaling on the LG B4 is assessed moderately positively. While there is no noticeable edge doubling, the image tends to be somewhat "soft." This can be adjusted by tweaking the sharpness slider to improve the clarity.

Digital video processing is unfortunately one of the weaker points of the TCL A400 Pro. That doesn't mean the TV performs badly, but it's hard to call it anything clearly above standard. The upscaling itself is adequate: edges are smoothed fairly well, the image doesn't look overly sharp or pixelated, and lower-quality content can be watched without major discomfort. At the same time the overall look is slightly soft and it lacks the precision that the best image processors in more expensive TVs can deliver.

Much worse, however, is its handling of tonal transitions caused by heavy compression. TCL equipped the A400 Pro with a "Gradual Smoothing" feature that in theory should reduce visible color banding and artifacts in lower-quality content. In practice its effectiveness is very limited. It does not improve tonal transitions in any noticeable way, and at higher settings it can also smooth out image details, giving the picture an artificial, slightly blurred character. For that reason we think it's best to leave this feature off. The A400 Pro handles basic image scaling decently, but if you often watch heavily compressed content with visible posterization, this model won't be one of the best choices.

The maximum refresh rate on the LG B4 is 120 Hz, the bare minimum for those requiring high image fluidity. The manufacturer has equipped the TV with a multi-stage motion smoother called "TruMotion." This feature is split into two sliders: one controls the sharpness of moving images (De-Blur) and the other adjusts judder (De-Judder). Both sliders can be set between 0 and 10, with each level affecting the smoothness, so users can easily find their preferred setting.

The LG OLED B4 panel boasts an impressive average response time of 0.1 ms (based on our measurements), delivering an exceptionally clear image that surpasses the capabilities of LCD TVs, which often have response times of several milliseconds. This is particularly noticeable in the "UFO Test" images, where no trailing blur is visible behind moving objects.

The TCL A400 Pro is equipped with a 144 Hz panel, but in practice we're most interested in how it performs at 120 Hz. That's the refresh rate used by most consoles today, as well as many sports broadcasts and high-frame-rate content. In this range the TV performs quite well. Motion clarity is really good, especially after properly configuring the motion smoothing. The "Motion Clarity" feature improves smoothness. Its settings include two sliders that let you tailor the motion smoothing to your preferences — separately for lower- and higher-frame-rate material. That way you can achieve either a more cinematic look or a noticeably smoother picture. If you don't want to tweak settings manually, you can use presets such as low, medium, high, cinema, or nature.

The LG B4 has four full HDMI 2.1 ports, each providing 48Gbps bandwidth. This ensures smooth activation of all relevant features without issues, making the television highly suitable for gaming. With its low input lag and extensive functionality, including well-implemented HGIG mode and Dolby Vision gaming with low latency, the B4 is a strong contender for gamers who demand high quality.

A standout feature is GameBar, which allows for on-the-fly adjustments without interrupting gameplay, as well as image adaptations for those with visual impairments. Another key point is that when VRR technology is enabled, the television maintains its contrast, thanks to the OLED panel's structure, though slight flickering in grey shades is to be expected.

In conclusion, the LG B4 is an ideal choice for gamers, seamlessly combining high performance with excellent gaming features. Its 120Hz panel and HDMI 2.1 ports make it a standout option for those seeking top-tier gaming experiences.

When it comes to features for gamers, the TCL A400 Pro performs excellently. The TV has practically everything you can expect from a gaming TV today: 4K support at high refresh rates, VRR, ALLM, correct implementation of HDR formats in games, including Dolby Vision, and HGiG. Because of that it works well with both next-gen consoles and PCs. Another plus is the inclusion of a Game Bar, a special panel with the most important settings for gamers. From it you can quickly check basic signal information, refresh rate, and active features, and also adjust the look and behavior of some settings to your own preferences. This is a solution that may not change picture quality by itself, but it greatly improves the convenience of using the TV while gaming.

The only thing to complain about is the number of full HDMI 2.1 ports. The A400 Pro has only two such ports out of four, and one of them also functions as eARC. In practice this means that if someone wants to connect two next-gen consoles and a soundbar, they may hit some limitations. In that scenario you'll have to either swap devices or use extra equipment, for example an AV receiver or a soundbar with HDMI inputs. Despite this, it's hard not to rate the A400 Pro very highly as a gaming TV. The gaming feature set here is really powerful.