Review: QN65Q9F, QN75Q9F (Samsung Q9F)

The flagship Samsung Q9F series comes in three screen sizes: the 65-inch QN65Q9F, the 75-inch QN75Q9F and the 88-inch QN88Q9F class model. Being part of the Samsung’s QLED range this year, the Q9F series TVs have the spectrum of their LED backlight enhanced by quantum dots. Even though that the QN65Q9F (and the two bigger models) are edge-lit TVs, they use the Infinite Array structure, which allows them to have more dimming zones than what is normally possible with edge-lit TVs.

In terms of DCI-P3 color space, the Q9F can show fully saturated colors in mid-tones, highlights and most shadows. Only in the very deepest shadows colors are not optimally saturated but not to an extend that would detract from otherwise remarkable color reproduction that the Samsung’s Quantum Dot technology is able to provide. Considering that this is a limitation of the LCD technology, rather than a Quantum Dot related issue, it only affects low stimulus levels. It also needs to be said that the quantum dots on the Q9F are utilized only for their photoluminescence property, rather than their electroluminescence. In other words, each model in the Q9F series is a transmissive display, rather than emissive (or a hybrid). The implication being is that LCD TVs cannot completely block the backlight when showing black color, so the minimum luminance level on the Q9F is not zero.

The utilization of quantum dots also contributes, albeit indirectly, for a deeper black level. Specifically, the quantum dots allow the Ultra Black filter to be used without the brightness output or color richness being affected. This layer is aimed at preserving deep black levels in brighter environments. The primary purpose of the quantum dots, however, is to optimize the spectrum of the backlight to match the color filters so that a wide color spectrum can be achieved at various luminance levels. Quantum dots that are 2 nanometers in size emit in the blue spectrum; 3 nanometers: in the green spectrum, and 6 nanometers: in the red spectral region. The narrow spectral peaks of emission also allow for a clear separation between the primary colors, therefore increasing their purity. The Q9F uses new alloyed quantum dots with multiple components, including a new metal shell, a new metal core, and a gradient shell.

The viewing angle is slightly wider than what you’d normally expect from a VA-type of panel that the QN65Q9F uses, provided the content itself contains vivid colors. Otherwise, the QN65Q9F’s off-axis performance is typical for an LCD TV with a VA-type of panel. It means that colors start to lose saturation and contrast degrades fairly quickly at an angle. Although quantum dots are able to mitigate this issue to some extend, they can do so only in limited number of situations, i.e. when the colors of the content are vivid.

The peak brightness in small specular highlights is up to 2,000cd/m2, depending on the picture preset used, and the color temperature of that preset. Even when a picture mode with a more neutral color temperature is used, the Q9F doesn’t need to quantize the dynamic range of HDR content mastered to 1,000cd/m2 because it can reach this level in small highlights. HDR10 mastered to 1,000cd/m2 is faithfully reproduced in terms of contrast range, and the Q9F can present it exactly the way the director intended. Furthermore, even though BT.2020 container is used, HDR content is typically graded in DCI-P3, which the Q9F covers fully (except for some of the lowest luminosity levels), meaning there isn’t any significant gamut mapping involved either. The same applies to HDR10 content mastered to 4,000cd/m2, except that there is a certain amount of tone-mapping involved because the Q9F cannot reach the maximum content light level (maxCLL) in that case. The HDR10 only contains static metadata, which limits the optimal performance to only scene with highlights. As a result, some scenes that only contain shadows and mid-tones might be rendered darker than ideal, but this is noticeable only in HDR10 content mastered to 4,000cd/m2.

Although the QN65Q9F is edge-lit, as opposed to being a full-array backlit, it has more dimming zones than the the step-down QN65Q7F and QN65Q8C models, for example. As a result, the QN65Q9F has a higher inter-image contrast ratio than the QN65Q7F and QN65Q8C during most scenes, provided the local dimming feature is used. The more precise control over light output in different zones of the screen also means that small specular highlights can get brighter on the QN65Q9F vs QN65Q7F and QN65Q8C. This is only relevant to HDR content, though, because SDR content is normally mastered to 100cd/m2. There is a fundamental difference between SDR and HDR content due to the gamma used with SDR being a relative luminance function, whereas the PQ (Perceptual Quantizer) EOTF (Electro-optical transfer function) is an absolute function that maps digital code words in the 10-bit HDR10 signal to a specific luminance values. In other words, you can make SDR content overall brighter by adjusting your TV settings, whereas you cannot do this with HDR content because the extra luminance is reserved to be used only in specular highlights.