In preparation for the calibration discussion, i'm re-posting a great review of the LG vs the Sony to point out the picture processing that Sony is performing so we can discuss how it might effect SDR and HDR calibration. Only the picture processing related parts of the review are below.
Review: Sony XBR65A1E, XBR55A1E (A1E)
The subject of this review is the Sony XBR65A1E. Since the 65-inch and the 55-inch class models have identical features, the following review applies to the XBR55A1E as well. Both of them are members of the A1E series of Sony OLED TVs.
The Sony XBR65A1E and the 2017 LG OLED TVs use the latest generation W-OLED panel. The resolution is 3840×2160, meaning there are more than 8 million individual pixels, with each and every one of them producing it own light. However, instead of having sub-pixels that emit distinct red, green and blue, the Sony XBR65A1E and LG OLED TVs produce dichromatic white light on a pixel level, which necessitates the use of color filters. The dichromatic light source results in less narrow peaks in the green, and especially the red spectral regions in comparison to the blue. Although this doesn’t prevent them from covering the DCI-P3 color space coverage almost entirely, it means that some improvements need to be made to the W-OLED technology in order for any future TVs using these type of panels to be able to fully cover the BT.2020 color space, which is significantly larger than DCI-P3.
Since OLED a self-emissive technology, individual pixels can be completely shut off so that no light is emitted. As a result, both the Sony XBR65A1E and its LG OLED counterparts have a perfect black level of 0 nits, provided there is no ambient light that gets reflected off the screen. At the opposite end of the brightness scale, they can reach approximately 150 nits on a full-field white (100% window size). Therefore, if you calibrate the Sony XBR65A1E or the LG OLED65E7P to the level SDR content is usually mastered to (i.e. 100 nits), the target luminance is achieved not only in small areas of the screen but also during scenes with high average picture level. A typical example of content with preponderance of bright elements is hockey.
Nonetheless, the Auto Brightness Limiter is still present, and starts to function at above 150 nits. It basically means that the larger the brightly illuminated portion of the screen is, the dimmer it gets. However, most SDR content has low-to-mid APL, so it is unlikely to notice any drop in luminance unless the scene is overly bright and you’ve calibrated your TV to more than 150 nits. Furthermore, the Sony XBR65A1E and the LG OLED65E7P can reach more than 300 nits in 50% window size, and more than 400 nits in 25% window size, meaning they can get sufficiently bright for viewing under high ambient light conditions, provided the SDR content doesn’t have high average picture level.
The peak brightness with High Dynamic range (HDR) content varies based on the HDR picture preset you’re using. Some of the HDR picture modes (e.g. Vivid) on the Sony XBR65A1E and LG track the D93 white point more closely, while others (e.g. Standard): the D65 white point. Although tracking the D93 white point provides a peak brightness of up to 1,000 nits in small specular highlights (5% window size), there is some significant blue tint added to the white color. On the other hand, the D65 white point ensures more neutral color temperature, but the peak brightness in small specular highlights (5% window size) is only up to 800 nits.
One of the HDR formats that the Sony XBR65A1E and LG OLED TVs support is HDR10. The transfer function used with the HDR10 is called Perceptual Quantizer (PQ). The digital code words in the 10-bit HDR10 signal correspond to specific luminance values, regardless of the actual brightness capability of the TV. In other words the PQ is an absolute transfer function. When the HDR10 content is mastered to a brightness level unattainable by the Sony XBR65A1E and LG, they resort to tone-mapping in order to quantize the dynamic range of the content. The tone-mapping process is not standardized, though. This means that there is a difference in how the Sony XBR65A1E and LG implement the PQ EOTF (Electro-Optical Transfer Function), especially at higher stimulus levels.
HDR10 content mastered to 4,000 nits requires the Sony XBR65A1E and LG OLED TVs to perform more tone-mapping than 1,000 nit HDR10 content, so this is where the difference between them is most prominent. Specifically, the LG OLED65E7P tends to start rolling-off the luminance a bit earlier than the Sony XBR65A1E, which allows for more detail in the highlights to be resolved, but also causes some tones in the diffuse white region to be rendered slightly darker in comparison to the Sony XBR65A1E.
It also needs to be said that HDR10 content is only optimized for scenes with highlights due to the fact that static metadata defines maxCLL (maximum content light level) which doesn’t change for the entire duration of the content. In an attempt to rectify this, the 2017 LG OLED TVs utilize Active HDR processing for analyzing individual frames, and generating dynamic metadata on the fly. The Sony XBR65A1E’s Dynamic Contrast Enhancer also performs frame-by-frame optimization. The setting which controls the Active HDR processing on the LG is called Dynamic Contrast, and it can be set to Low, Medium, High or Off, so you can find the right balance between preventing the dynamic range from being unnecessary compressed during scenes without highlights, on the one hand, and avoiding any further alternation of the director’s intended look (besides the one already introduced by the tone-mapping), on the other.
There is no such dilemma with Dolby Vision content because the dynamic metadata is generated during post-production, so it conforms director’s intentions. Another advantage over the HDR10 is that the Dolby’s mapping engine is aware of the specific characteristics (such as peak brightness, color volume, etc) of the display, meaning it can provide better tone-mapping. The LG OLED TVs support Dolby Vision out of the box whereas the Sony XBR65A1E requires a future firmware update to enable support for this format. According to Sony, the update will be available later this year. It will also bring support for HLG (Hybrid Log Gamma), which is a different format of HDR aimed primarily at TV broadcasts, to the Sony XBR65A1E. The 2017 LG OLED TVs support HLG out of the box.
Considering that color bit depth and DCI-P3 gamut coverage are tied to the panel of the TV, rather than video processing, it’s not surprising that color rendition is mostly identical on the Sony XBR65A1E and LG. The panel bit depth is 10-bit, meaning both of them are able to show more than a billion color shades. The DCI-P3 color space coverage is approximately 99% for the mid-tones, and slightly lower for specular highlights that are above 1,000 nits. Therefore, the Sony XBR65A1E and LG OLED TVs do not render some of the brightest colors in specular highlight as vivid as they should be. Unlike the Sony XBR65A1E, the LG OLED TVs have a Color Management System, so you can adjust saturation, tint and luminance independently for the primary colors. Although this may improve the color accuracy, it doesn’t lead to an expansion in the DCI-P3 coverage.
Neither of them has any significant trouble with the transition from black to dark gray, which was somewhat problematic with earlier OLED TVs. The smooth near-black gradation is a result from both improvements in the panel itself, as well as the fact the processing is done at a higher bit depth, so that quantazation errors can be avoided. Specifically, the Sony XBR65A1E features Super Bit Mapping, which upconverts 8-bit or 10-bit source content for 14-bit processing. The Smooth Gradation menu setting controls it. The LG OLED TVs also resorts to processing content at a higher bit depth in order to prevent macroblocking artifacts near-black. The black level setting is non-linear in order to provide more granular control over the transition from black to dark gray.
One of the areas where the more advanced video processing on Sony XBR65A1E vs LG becomes apparent is upscaling lower resolution content to 4K resolution. This is attributed to the fact that the X1 Extreme image processor on the Sony XBR65A1E can access tens of thousands picture patterns in two databases. One of the Sony’s propriety databases is dedicated to noise reduction while the other is for super resolution (i.e. enhancing the clarity of upscaled content). The before and after data references allow the Sony XBR65A1E to identify compression noise and other artifacts in the source, and remove them in an optimal way. Whilst not quite on par with the Sony XBR65A1E, the LG upscaling is also good. Furthermore, if you’re watching native 4K content, or even some pristine quality 1080p content, such as Blu-ray discs, the difference between the Sony XBR65A1E and LG OLED65E7P is minimal.
The enhanced video processing on the Sony XBR65A1E also leads to less visible artifacts when the motion compensated frame interpolation is engaged. Although this model is not impulse driven (like plasma TVs were), the nearly instantaneous pixel response time and the 120Hz native refresh rate, which LG OLED TVs also have, prevent fast moving objects from having dark trails. Since individual frames remain on the screen until the next refresh – a method known as sample-and-hold, and used by both the Sony XBR65A1E and LG OLED TVs, some blurring is still possible, depending on the specific content. The reason is that your eyes are moving as they track an object traveling across the screen whereas the frame doesn’t change until the next refresh, which happens every 8.3 ms for 120Hz TVs.
The Object-based HDR remaster is applied across most of the Sony XBR65A1E SDR picture presets in order for color and contrast of non-HDR content, such as Blu-ray discs, DVDs, and TV broadcasts to be enhanced. On the other hand, LG OLED TVs have a dedicated picture preset called HDR Effect. The advantage to the Sony XBR65A1E’s method of individually analyzing and remastering objects is that the average picture level doesn’t need to lowered significantly in order to provide headroom for highlights, which LG OLED TVs are somewhat prone to when HDR Effect is used.
The Sony XBR65A1E uses Android TV (version 6.0) whereas 2017 LG OLED TVs rely on the WebOS 3.5 system for their smart TV capabilities. The Sony XBR65A1E allows you to access compatible apps on Google Play. There is a built-in microphone in the remote and a future firmware update will enable Google Assistant on the Sony XBR65A1E. The LG motion-sensing Magic Remote also has a built-in microphone, and the webOS platform is very intuitive to use.