Comparison TCL 55C745 55 " vs TCL 55C735 55 "

The maximum brightness of the image provided by the TV screen.

The image on the screen should be bright enough so that you do not have to strain your eyes unnecessarily to view it. However, too high brightness is undesirable — it will also lead to fatigue. The optimal brightness level depends on the surrounding conditions: the more intense the ambient light, the brighter the TV screen should be. So, on a sunny day, the screen may have to be “turned up” to the maximum, and in the evening, in dimmed light, a relatively dim image will be more comfortable. In addition note that large screens require higher brightness, since they are designed for a greater distance from the viewer.

Thus, the higher the number in this paragraph, the greater the margin of brightness this model has, the better it will show itself in intense ambient light. The lowest indicator sufficient for more or less comfortable viewing in any conditions is 300 cd/m² for models with a diagonal of up to 32", 400 cd/m² for models in the range of 32 – 55" and 600 cd/m² for large screens of 60" and more. In this case, the brightness margin anyway will not be superfluous. But with lower indicators, you may have to darken the room somewhat for comfortable viewing.

The level of static contrast provided by the TV screen.

Contrast in a general sense is the ratio in brightness between the brightest whites and the darkest blacks that the screen can produce. Other things being equal, the higher the screen contrast, the better the quality of colour reproduction and detail, the lower the likelihood that it will be impossible to see details in too bright or too dark areas of the image. Static contrast, on the other hand, describes the maximum difference in brightness that can be achieved within one frame without changing the brightness of the image — this is its difference from dynamic contrast (see below).

The values of static contrast are much lower than those of dynamic, but this characteristic is the most "honest". It is on it that the properties of the image seen on the screen at a particular moment depend, it is describes the basic properties of the screen, without taking into account the software tricks provided by the manufacturer in the hardware of the TV.

The level of dynamic contrast provided by the TV screen.

Contrast in a general sense is the ratio in brightness between the brightest whites and the darkest blacks that the screen can produce. Other things being equal, the higher the screen contrast, the better the quality of colour reproduction and detail, the lower the likelihood that it will be impossible to see details in too bright or too dark areas of the image. Formally, the main characteristic of screens is static contrast (see above), but even in advanced matrices it is relatively low. Therefore, manufacturers went to the trick, introducing such a characteristic as "dynamic contrast".

Dynamic contrast ratio is the difference between the brightest whites at the highest screen brightness settings and the darkest blacks at the lowest. These contrast ratios can be quite impressive—much higher than static—however, it is impossible to achieve such values within a single frame, and dynamic contrast ratio is stated more for promotional purposes than for describing the actual specifications of the screen. However, it cannot be said that this indicator is completely unrelated to reality. The fact is that many TVs use automatic brightness control, which changes the settings depending on the characteristics of the image. This control is based on the fact that when displaying bright scenes, there is no need to provide a deep black level, and in dark scenes, high brightness of light areas is not needed — th...ese are the features of the human eye. This means that in bright scenes you can increase the overall brightness, and in dark scenes you can reduce it; the maximum brightness difference achievable in this mode of operation is precisely described by dynamic contrast.

The response time can be described as the maximum time required for each pixel of the screen to change brightness, in other words, the longest time from the receipt of a control signal to the pixel until it switches to the specified mode. The actual switching time may be less — if the brightness changes slightly, it can be calculated in microseconds. However, it is the longest time that matters — it describes the guaranteed response speed of each pixel.

First of all, the frame rate is directly related to the response time (see the relevant paragraph): the lower the response time, the higher the frame rate can be provided on this sensor. However, the actual frame rate may be less than the theoretical maximum, it all depends on the TV. Also note that the overall image quality in dynamic scenes depends primarily on the frame rate. Therefore, we can say that the response time is an auxiliary parameter: the average user rarely needs this data, and in the specifications they are given mainly for advertising purposes.

Dynamic Scene Index (DSI) provided by the TV screen.

DSI is a rather specific parameter that can be called "visible framerate". Its appearance is due to the fact that a high frame rate is highly desirable for dynamic scenes — it provides smooth images and good detail of moving objects. However, for technical reasons, it is not possible to achieve indicators above 200 Hz in most screens. In order to remedy the situation, manufacturers use special technologies that create the effect of increasing the frame rate.

Such technologies may have different names, but they have the same principle of operation — inserting additional frames between the "own" frames of the video being played. And the dynamic scene index describes the overall effectiveness of such technology used in a TV. For example, a DSI of 200 Hz means that the image quality on the screen approximates a frame rate of 200 Hz, although the actual frame rate is often as low as 50-60 Hz.

In the most advanced models, the dynamic scene index can be up to 3000 Hz, and options above 3000 Hz are considered to be TVs with a high dynamic scene index. However, it is worth noting that such specifications are more of an advertising ploy than a real advantage: in fact, the threshold for human perception is 400 – 500 Hz, a further increase in the DSI does not give a clearly visible improvement in the image.

TV support for high dynamic range technology — HDR.

This technology is designed to expand the range of brightness reproduced by the TV; Simply put, an HDR model will display brighter whites and darker blacks than a regular TV. In fact, this means a significant improvement in colour quality. On the one hand, HDR provides a very "live" image, close to what the human eye sees, with an abundance of shades and tones that a normal screen cannot convey; on the other hand, this technology allows to achieve very bright and rich colours.

However for the full use of this feature, you need not only an HDR TV, but also content (movies, TV broadcasts, etc.) that was originally created for HDR. Also note that there are several different HDR technologies that are not compatible with each other. Therefore, when buying a TV with this feature, it is highly advisable to clarify which version of HDR it supports (HDR10, HDR10 + or Dolby Vision). And the following are found:

— HDR10. Historically the first of the consumer HDR formats, less advanced than the options described below but extremely widespread. In particular, HDR10 is supported by almost all streaming services that provide HDR content, and it is also common for Blu-ray discs. Allows to work with a colour depth of 10 bits (hence the name). At the same time, devices of this format are also compatible wi...th content in HDR10+, although its quality will be limited by the capabilities of the original HDR10.

— HDR10+. An improved version of HDR10. With the same colour depth (10 bits), it uses the so-called dynamic metadata, which allows transmitting information about the colour depth not only for groups of several frames, but also for individual frames. This results in an additional improvement in colour reproduction.

– Dolby Vision. An advanced standard used particularly in professional cinematography. Allows to achieve a colour depth of 12 bits, uses the dynamic metadata described above, and also makes it possible to transmit two image options at once in one video stream — HDR and standard (SDR). At the same time, Dolby Vision is based on the same technology as HDR10, so in modern video technology this format is usually combined with HDR10 or HDR10+.

TV compatibility with special frame synchronization technologies used in AMD graphics cards.

You should pay attention to this parameter if you plan to use the TV as a gaming monitor for a PC or laptop with an AMD graphics adapter. Special timing technologies are used to match the screen refresh rate to the frame rate of the incoming video signal. Such a need arises for the reason that the frame rate issued by the graphics card can “float” when the load on the video adapter changes (this is especially true for demanding games); and if this frequency does not match the screen refresh rate – tears and other unwanted artifacts appear on the image.

The AMD technology used to eliminate this effect is called FreeSync. Nowadays, it is presented on the market in three versions — the original FreeSync and two extended ones:

– AMD FreeSync Premium Pro. The most advanced and functional version, formerly known as AMD FreeSync 2 HDR. In addition to refresh rate sync, it also includes support for HDR (see above), output at a frame rate of at least 120 Hz at Full HD resolution, as well as low frame rate compensation (LFC). The essence of LFC is that when the frame rate of the original video signal falls below the minimum frequency supported by the screen, the same frame is displayed on the screen several times, which allows to maintain the maximum smoothness of the “picture”.

— AMD FreeSync Premium. A somewhat s...implified version compared to FreeSync Premium Pro. It does not provide working with HDR, otherwise it is completely similar.

The brand of the speaker system installed in the TV.

This item is indicated if the TV is equipped with advanced sound system, which is noticeably superior in quality to conventional speakers. Such information further emphasizes the high level of the device. At the same time, the specifications usually do not contain the full name of the speaker system, but only the brand name — for example, Bang & Olufsen, Harman Kardon, JBL, etc.: even such information is quite enough in this case.

The nominal power of the sound produced by the TV's sound system.

The larger the screen and the greater the estimated distance to the viewer, the more powerful the sound system must be in order to be heard normally. Manufacturers take this moment into account, moreover, most often they also provide a solid volume margin. So if a TV is bought for home viewing in a quiet, calm environment, you can not pay much attention to the sound power: it is guaranteed to be enough for such a usage. It makes sense to specifically look for models with high-power speakers for a noisy environment — for example, a cafe or other public space. Detailed recommendations on this matter can be found in special sources, but here we note that even in such cases, connecting external speakers can be a good alternative.