2 inch tft lcd power consumption quotation

We are changing our TFT part numbers to have them better describe the parts being ordered. The change should be complete for all TFT modules shipping within the next six months.

The power consumption of computer or tv displays vary significantly based on the display technology used, manufacturer and build quality, the size of the screen, what the display is showing (static versus moving images), brightness of the screen and if power saving settings are activated.

Click calculate to find the energy consumption of a 22 inch LED-backlit LCD display using 30 Watts for 5 hours a day @ $0.10 per kWh. Check the table below and modify the calculator fields if needed to fit your display.

Hours Used Per Day: Enter how many hours the device is being used on average per day, if the power consumption is lower than 1 hour per day enter as a decimal. (For example: 30 minutes per day is 0.5)

LED & LCD screens use the same TFT LCD (thin film transistor liquid crystal display) technology for displaying images on the screen, when a product mentions LED it is referring to the backlighting. Older LCD monitors used CCFL (cold cathode fluorescent) backlighting which is generally 20-30% less power efficient compared to LED-backlit LCD displays.

The issue in accurately calculating the energy consumption of your tv or computer display comes down to the build quality of the screen, energy saving features which are enabled and your usage patterns. The only method to accurately calculate the energy usage of a specific model is to use a special device known as an electricity usage monitor or a power meter. This device plugs into a power socket and then your device is plugged into it, electricity use can then be accurately monitored. If you are serious about precisely calculating your energy use, this product is inexpensive and will help you determine your exact electricity costs per each device.

In general we recommend LED displays because they offer the best power savings and are becoming more cheaper. Choose a display size which you are comfortable with and make sure to properly calibrate your display to reduce power use. Enable energy saving features, lower brightness and make sure the monitor goes into sleep mode after 5 or 10 minutes of inactivity. Some research studies also suggest that setting your system themes to a darker color may help reduce energy cost, as less energy is used to light the screen. Also keep in mind that most display will draw 0.1 to 3 watts of power even if they are turned off or in sleep mode, unplugging the screen if you are away for extended periods of time may also help.

LCD stands for “Liquid Crystal Display” and TFT stands for “Thin Film Transistor”. These two terms are used commonly in the industry but refer to the same technology and are really interchangeable when talking about certain technology screens. The TFT terminology is often used more when describing desktop displays, whereas LCD is more commonly used when describing TV sets. Don’t be confused by the different names as ultimately they are one and the same. You may also see reference to “LED displays” but the term is used incorrectly in many cases. The LED name refers only to the backlight technology used, which ultimately still sits behind an liquid crystal panel (LCD/TFT).

As TFT screens are measured differently to older CRT monitors, the quoted screen size is actually the full viewable size of the screen. This is measured diagonally from corner to corner. TFT displays are available in a wide range of sizes and aspect ratios now. More information about the common sizes of TFT screens available can be seen in our section about resolution.

The aspect ratio of a TFT describes the ratio of the image in terms of its size. The aspect ratio can be determined by considering the ratio between horizontal and vertical resolution.

16:9 = wide screen formats such as 1920 x 1080 and 2560 x 1440. 16:9 is commonly used for multimedia displays and TV’s and is increasingly becoming the standard

Ultra-high resolution panels will offer varying aspect ratios including Ultra HD (3840 x 2160 = 16:9), 4K (4096 x 2160 = an odd 1:9:1 aspect ratio) and 5K (5120 x 2880 = 16:9)

The resolution of a TFT is an important thing to consider. All TFT’s have a certain number of pixels making up their liquid crystal matrix, and so each TFT has a “native resolution” which matches this number. It is always advisable to run the TFT at its native resolution as this is what it is designed to run at and the image does not need to be stretched or interpolated across the pixels. This helps keep the image at its most clear and at optimum sharpness. Some screens are better than others at running below the native resolution and interpolating the image which can sometimes be useful in games.

You generally cannot run a TFT at a resolution of above its native resolution although some screens have started to offer “Virtual” resolutions, for example “virtual 4k” where the screen will accept a 3840 x 2160 input from your graphics card but scale it back to match the native resolution of the panel which is often 2560 x 1440 in these examples. This whole process is rather pointless though as you lose a massive amount of image quality in doing so.

Make sure your graphics card can support the desired resolution of the screen you are choosing, and based on your uses. If you are a gamer, you may want to consider whether your graphics card can support the resolution and refresh rate you will want to use to power your screen. Also keep in mind whether you are planning to connect external devices and the resolution they are designed to run at. For instance if you have a 16:10 format screen and plan to use an external device which runs at 16:9, you will need to ensure the screen is able to scale the image properly and add black borders, instead of distorting the aspect ratio of the image.

Ultra-high resolutions must be thought of in a slightly different way. Ultra HD (3840 x 2160) and 4K (4096 x 2160) resolutions are being provided nowadays on standard screen sizes like 24 – 27” for instance. Traditionally as you increased the resolution of panels it was about providing more desktop real estate to work with. However, with those resolutions being so high, and the screen size being relatively small still, the image and text becomes incredibly small if you run the screen at normal scaling at those native resolutions. For instance imagine a 3840 x 2160 resolution on a 24” screen compared with 1920 x 1080. The latter would probably be considered a comfortable font size for most users. These ultra-high resolutions nowadays are about improving image clarity and sharpness, and providing a higher pixel density (measured as pixels per inch = PPI). In doing so, you can improve the sharpness and clarity of an image much like Apple have famously done with their “Retina” displays on iPads and iPhones. To avoid complications with tiny images and fonts, you will then need to enable scaling in your operating system to make everything easier to see. For instance if you enabled scaling at 150% on a 3840 x 2160 resolution, you would end up with a screen real estate equivalent to a 2560 x 1440 panel (3840 / 1.5 = 2560 and 2160 / 1.5 = 1440). This makes text much easier to read and the whole image a more comfortable size, but you then get additional benefits from the higher pixel density instead, which results in a sharper and crisper image.

More and more you will see resolutions referred to by their common HD equivalents, particularly when it comes to TV’s. HD content is based purely on the resolution of the source and is commonly defined by the number of pixels vertically in the resolution. i.e. a 720 HD source has 720 vertical pixels in it’s resolution and a 1080 will have 1080. On top of this, there are two ways of showing this content, either using a progressive scan (e.g. 1080p) or an interlaced scan (1080i).

To display this content of this type, your screen needs to be able to 1) handle the full resolution naturally within its native resolution, and 2) be able to handle either the progressive scan or interlaced signal over whatever video interface you are using. If the screen cannot support the full resolution, the image can still be shown but it will be scaled down by the hardware and you won’t be take full advantage of the high resolution content. So for a monitor, if you want to watch 1080 HD content you will need a monitor which can support at least a vertical resolution of 1080 pixels, e.g. a 1920 x 1080 monitor.

This has given rise to modern Ultra HD standards and terms like 4K and 5K. Ultra HD is a term for monitors with a 3840 x 2160 resolution, that being four times the resolution of Full HD 1920 x 1080. Screens with this Ultra HD resolution are often referred to as “4K” as well, although strictly that should only be used for screens with 4092 x 2160 resolution (4K representing the vertical resolution here). There are also some 5K capable monitors produced which offer 5120 x 2880 resolution (5K here representing the vertical resolution). Please see the following sections which talk about Pixel Pitch and PPI and will help you understand these higher resolutions in more detail.

Unlike on CRT’s where the dot pitch is related to the sharpness of the image, the pixel pitch of a TFT is related to the distance between pixels. This value is fixed and is determined by the size of the screen and the native resolution (number of pixels) offered by the panel. Pixel pitch is normally listed in the manufacturers specification. Generally you need to consider that the ‘tighter’ the pixel pitch, the smaller the text will be, and potentially the sharper the image will be. To be honest, monitors are normally produced with a sensible resolution for their size and so even the largest pixel pitches return a sharp images and a reasonable text size. Some people do still prefer the larger-resolution-crammed-into-smaller-screen option though, giving a smaller pixel pitch and smaller text. It’s down to choice and ultimately eye-sight.

For instance you might see a 35″ ultra-wide screen with only a 2560 x 1080 resolution which would have a 0.3200 mm pixel pitch. Compare this to a 25″ screen with 2560 x 1400 resolution and 0.2162 mm pixel pitch and you can see there will be a significant different in font size and image sharpness. There are further considerations when it comes to the pixel pitch of ultra-high resolution displays like Ultra HD and 4K. See the section on PPI for more information.

Resolution is typically thought as a factor which determines the screen area or screen “real estate” you will have available. In years gone by as panel sizes increased, resolutions were increased as well and so bigger screens could offer you more desktop space to work with. Split-screen working and high resolution image work become more and more possible. This is fine up to a point, but pushing resolution for the purposes of delivering more desktop real-estate reaches a point where it becomes somewhat impractical for desktop monitors. For instance, a 40″ 3840 x 2160 resolution delivers a comfortable pixel pitch and font size natively (very similar to a 27″ at 2560 x 1440), so if you wanted a higher resolution than this you would have to increase the screen size again probably. You start to reach the point where sitting close to a screen so large becomes impractical.

Instead manufacturers are now focusing on delivering higher resolutions in to existing panel sizes, not for the purpose of providing more desktop real-estate, but for the purpose of improving image sharpness and picture quality. Apple started this trend with their “Retina Displays” used in iPads and iPhones, improving image sharpness and clarity massively. It is common now to see smaller screens such as 24″ and 27″ for instance, but with high resolutions like 3840 x 2160 (Ultra HD) or even 5120 x 2880 (5K). By packing more pixels in to the same screen size which would typically offer a 2560 x 1440 resolution, panel manufacturers are able to provide much smaller pixel pitches and improve picture sharpness and clarity. To measure this new way of looking at resolution you will commonly see the spec of ‘Pixels Per Inch’ (PPI) being used.

Of course the problem with this is that if you run a screen as small as 27″ with a 5K resolution, the font size is absolutely tiny by default. You get a massive boost of desktop real-estate, just like when moving from 1920 x 1080 to 2560 x 1440, but that’s not the purpose of these higher resolutions now. To overcome this you need to use the scaling options in your Operating System software to scale the image and make it more usable. Windows provides for instance scaling options like 125% and 150% within the control panel. On a 3840 x 2160 Ultra HD resolution if you use a 150% scaling option for example you will in effect reduce the desktop area by a third, resulting in the same desktop area as a 2560 x 1440 display (i.e. 2560 x 150% = 3840). The OS scaling makes font sizes more comfortable and reasonable, but you maintain the sharp picture quality and small pixel pitch of the higher resolution panel. A 3840 x 2160 res panel scaled at 150% in Windows will look sharper and crisper than a 2560 x 1440 native panel without scaling, despite the fact both would have the same effective desktop area available.

Scaling via your OS is not the same as scaling from your monitor. If you just simply ran the screen at a lower resolution like 2560 x 1440 within the resolution section of your graphics card, the image gets interpolated by the monitor scaler instead. You get the same end result of a 2560 x 1440 sized desktop area size, but the image clarity is lost and you lose a lot of sharpness. The monitor is doing the interpolation for you here. Instead you run the screen at the full 3840 x 2160 resolution in the graphics card settings and allow the OS scaling control to increase font size and make the image useable.

While this aspect is not always discussed by display manufacturers it is a very important area to consider when selecting a TFT monitor. The LCD panels producing the image are manufactured by many different panel vendors and most importantly, the technology of those panels varies. Different panel technologies will offer different performance characteristics which you need to be aware of. Their implementation is dependent on the panel size mostly as they vary in production costs and in target markets. The four main types of panel technology used in the desktop monitor market are:

TN Film was the first panel technology to be widely used in the desktop monitor market and is still regularly implemented in screens of all sizes thanks to its comparatively low production costs. TN Film is generally characterized by good pixel responsiveness making it a popular choice for gamer-orientated screens. Where overdrive technologies are also applied the responsiveness is improved further. TN Film panels are also available supporting 120Hz+ refresh rates making them a popular choice for stereoscopic 3D compatible screens. While older TN Film panels were criticized for their poor black depth and contrast ratios, modern panels are actually very good in this regard, often producing a static contrast ratio of up to 1000:1. Perhaps the main limitation with TN Film technology is its restrictive viewing angles, particularly in the vertical field. While specs on paper might look promising, in reality the viewing angles are restrictive and there are noticeable contrast and gamma shifts as you change your line of sight. TN Film panels are normally based around a 6-bit colour depth as well, with a Frame Rate Control (FRC) stage added to boost the colour palette. They are often excluded from higher end screens or by colour enthusiasts due to this lower colour depth and for their viewing angle limitations. TN Film panels are regularly used in general lower end and office screens due to cost, and are very popular in gaming screens thanks to their low response times and high refresh rate support. Pretty much all of the main panel manufacturers produce TN Film panels and all are widely used (and often interchanged) by the screen manufacturers.

IPS was originally introduced to try and improve on some of the drawbacks of TN Film. While initially viewing angles were improved, the panel technology was traditionally fairly poor when it came to response times and contrast ratios. Production costs were eventually reduced and the main investor in this technology has been LG.Display (formerly LG.Philips). The original IPS panels were developed into the so-called Super IPS (S-IPS) generation and started to be more widely used in mainstream displays. These were characterized by their good colour reproduction qualities, 8-bit colour depth (without the need for Frame Rate Control) and very wide viewing angles. These panels were traditionally still quite slow when it came to pixel response times however and contrast ratios were mediocre. In more recent years a change was made to the pixel alignment in these IPS panels (see our detailed panel technology article for more information) which gave rise to the so-called Horizontal-IPS (H-IPS) classification. With the introduction of overdrive technologies, response times were improved significantly, finally making IPS a viable choice for gaming. This has resulted more recently in IPS panels being often regarded as the best all-round technology and a popular choice for display manufacturers in today’s market. Improvements in energy consumption and reduced production costs lead to the generation of so-called e-IPS panels. Unlike normal 8-bit S-IPS and H-IPS classification panels, the e-IPS generation worked with a 6-bit + FRC colour depth. Developments and improvements with colour depths also gave rise to a generation of “10-bit” panels with some manufacturers inventing new names for the panels they were using, including the co-called Performance-IPS (p-IPS). It is important to understand that these different variants are ultimately very similar and the names are often interchanged by different display vendors. For more information, see our detailed panel technologies guide.

The original early VA panels were quickly scrapped due to their poor viewing angles, and in their place came the two main types of VA matrix. Multi-Domain Vertical Alignment (MVA) and Patterned Vertical Alignment (PVA) panels. These VA variants were characterized by their reasonably wide viewing angles, being better than TN Film but not as wide as IPS. They were originally poor when it came to pixel response times but offered 8-bit colour depths and the best static contrast ratios of all the technologies discussed here. Traditionally VA panels were capable of static contrast ratios of around 1000 – 1200:1 but this has even been improved now to 3000:1 and above. Until very recently VA panels remained very slow and so were not really suitable for gaming. However during 2012 we saw advancements with the latest generation of VA panels and through the use of overdrive technologies this has been significantly improved. Perhaps the main limitation with VA panels is still their viewing angles when compared with popular IPS panel options. Gamma and contrast shifts can be an issue and the technology also suffers from an inherent off-centre contrast shift issue which can be distracting to some users. Through the years we have seen several different generations of VA panels. AU Optronics are the main manufacturer of MVA matrices, and we have seen the so-called Premium-MVA (P-MVA) and Advanced-MVA (AMVA) generations emerge. Chi Mei Innolux (previously Chi Mei Optoelectronics / CMO) also make their own variant of MVA which they call Super-MVA (S-MVA).The only manufacturer of PVA panels is Samsung as it is their own version of VA technology. We have seen several generations from them including Super-PVA (S-PVA) and cPVAandSVA. For more information, see our detailed panel technologies guide.

This technology was developed by Sharp for use in some of their TFT displays. It consists of several improvements that Sharp claim to have made, mainly to counter the drawbacks of the popular TN Film technology. They have introduced an Anti-Glare / Anti-Reflection (AGAR) screen coating which forms a quarter-wavelength filter. Incident light is reflected back from front and rear surfaces 180° out of phase, thus canceling reflection rather diffusing it as others do. As well as reducing glare and reflection from the screen, this is marketed as being able to offer deeper black levels. Sharp also claim to offer better contrast ratios than any competing technology (VA and IPS); but with more emphasis on improving these other technologies, this is probably not the case with more modern panels. There are very few ASV monitors around really, with the majority of the market being dominated by TN, VA and IPS panels.

This technology was developed by BOE Hydis, and is not really very widely used in the desktop TFT market, more in the mobile and tablet sectors. It is worth mentioning however in case you come across displays using this technology. It was developed by BOE Hydis to offer improved brightness and viewing angles to their display panels and claims to be able to offer a full 180/180 viewing angle field as well as improved colours. This is basically just an advancements from IPS and is still based on In Plane technology. They claim to “modify pixels” to improve response times and viewing angles thanks to improved alignment. They have also optimised the use of the electrode surface (fringe field effect), removed shadowed areas between pixels, horizontally aligned electric fields and replaced metal electrodes with transparent ones. More information about AFFS can be found here.

This panel technology was developed by NEC LCD, and is reported to offer wide viewing angles, fast response times, high luminance, wide colour gamut and high definition resolutions. Of course, there is a lot of marketing speak in there, and the technology is not widely employed in the mainstream monitor market. Wide viewing angles are possible thanks to the horizontal alignment of liquid crystals when electrically charged. This alignment also helps keep response times low, particularly in grey to grey transitions. Their SFT range also offers high definition resolutions and are commonly used in medical displays where extra fine detail is required.

NEC’s SFT technology was first developed to be labelled as Advanced-SFT (A-SFT) which offered enhanced luminance figures. This then developed further to Super Advanced-SFT (SA-SFT) where colour gamut reached 72% of the NTSC colour space, and then to Ultra Advanced-SFT (UA-SFT) where the gamut was still at 72% or higher, but with a further enhancement of the luminance as compared with SA-SFT. These changes were all made possible thanks to the improved transmissivity of the SFT technology. More information is available from NEC LCD

Do not rely entirely on response time specs quoted by manufacturers as a be all and end all to the monitor’s performance. Different manufacturers have different ways of measuring their response time, and one 5ms panel might not be the same in real use to another 5ms panel for instance. Panel technology also plays a part here, and don’t get confused with standard response times and grey to grey (G2G) figures. However, response times can be treated a guide to the performance of the screen, and as a rule of thumb, the lower the better.

Take for instance this example response time graph (rise times from 0 > x) I have put together. The X-axis defines the grey scale ranging from code 0 to code 255, and the Y-axis shows the response time across this range. As you progress to the right of the graph, the transitions are getting progressively lighter. So for instance at code 100 the transition is from black > dark grey, but at code 200 the transition is from black > light grey. At code 255, this is the change from black > white and is traditionally the fastest transition. It is the fastest because this is the widest change and therefore the largest voltage is applied to the liquid crystals. For many years, manufacturers have quoted the fastest transition of the panel as the figure for ‘response time’. This was always at the black > white > black transition and so this became accepted as the ISO standard norm for measuring response time. If this graph were a real panel, it would very likely be quoted as a 10ms screen and shows a characteristic curve for a traditional, non-overdriven, TN Film panel.

As you can see from the graph, the actual response time can vary quite considerably across the whole grey range, with some changes being much slower. This is the reason you cannot always rely on quoted specs to give an accurate representation of a screens actual pixel response performance. The quoted figures from manufacturers should be treated as a rough guide however to a panels response time, as generally there has been some improvements in the overall latency with the changes from 25ms > 16ms > 12ms > 8ms > 5ms panel generations for instance. The shape of the graph is likely to remain quite similar, but overall, the curve will probably be a little lower when comparing an 8ms to a 16ms for instance. Overall it won’t be twice as fast though.

One thing to note regarding pixel response time is that the overall performance of the TFT will also depend on the technology of the panel used. TN film panels offer response time graphs similar to that above, but screens based on traditional VA / IPSvariant panels can show response time graphs more like this (we are assuming for now non-overdriven panels):

This is again a mock up, but shows a typical curve shape you may expect from a VA / IPS panel (not using overdrive) when compared with TN film. Although a VA/IPS screen might be quoted as perhaps 12ms for instance, this might not mean it is as reactive as a 12ms TN film panel. Again, it is a good idea to check for reviews which measure the response time across the whole range as well as to consider real-life responsiveness tests such as those we carry out in our reviews.

Overdrive or ‘Response Time Compensation’ (RTC) is a technology which is designed to boost the response times of pixels across all transitions, with particular focus on improving the grey to grey changes which is the most important as those transitions are far more common in real-life uses. It is achieved by sending an over-voltage to the pixels to make them change orientation more quickly. While the full black > white change remains largely unchanged (since it already received the maximum voltage anyway), improvements across other transitions are often dramatic. With the introduction of overdriven panels the ISO point is not always the fastest transition any more, and so if a monitor has a response time quoted as “grey to grey / G2G” then you can be pretty certain it is using overdrive technology. The manufacturers still want to quote the fastest response time of their panel and show the improvements they have made though, but be wary of this change away from the ISO standard of quoting response times. The ISO response times have hit a wall really with TN Film stuck at 5 – 8ms, IPS stuck at around 16ms and MVA/PVA stuck at about 12ms. However, with the introduction of overdrive technologies, the more important grey to grey transitions are now significantly improved, and response times of 1 – 5ms G2G are now common place. These technologies have allow significant improvements in all panel technologies, but particularly in IPS and VA panels where response times were previously poor.

Some reviews sites including TFTCentral have access to advanced photosensor (photodiodе + low-noise operational amplifier) and oscilloscope measurement equipment which allows them to measure response time as detailed above. See our article about response times for more information on that method. Graphs showing response time according to their equipment are produced. Other sites rely on observed responsiveness to compare how well a panel can perform in practice and what a user might see in normal use. We think it is important to study both methods if possible to give a fuller picture of a panels performance. For visual tests TFTCentral uses a program called PixPerAn (developed by Prad.de) which is good for comparing monitor responsiveness with its series of tests. The favourite seems to be the moving car test as shown here:

In addition to pixel response time measurements and visual tests described above, it is also possible to capture the levels of blurring and smearing the human eye will experience on a display. This is achieved using a pursuit camera setup. They are simply cameras which follow the on-screen motion and are extremely accurate at measuring motion blur, ghosting and overdrive artefacts of moving images. Since they simulate the eye tracking motion of moving eyes, they can be useful in giving an idea of how a moving image appears to the end user. It is the blurring caused by eye tracking on continuously-displayed refreshes (sample-and-hold) that we are keen to analyse with this new approach. This is not pixel persistence caused by response times; but a different cause of display motion blur which cannot be captured using static camera tests. Low response times do have a positive impact on motion blur, and higher refresh rates also help reduce blurring to a degree. It does not matter how low response times are, or how high refresh rates are, you will still see motion blur from LCD displays under normal operation to some extent and that is what this section is designed to measure. Further technologies specifically designed to reduce perceived motion blur are required to eliminate the blur seen on these type of sample-and-hold displays which we will also look at.

These tests capture the kind of blurring you would see with the naked eye when tracking moving objects across the screen (example from the Asus ROG Swift PG279Q). As you increase the refresh rate the perceived blurring is reduced, as refresh rate has a direct impact on motion blur. It is not eliminated entirely due to the nature of the sample-and-hold LCD display and the tracking of your eyes. No matter how fast the refresh rate and pixel response times are, you cannot eliminate the perceived motion blur without other methods.Tests like the above would give you an idea of the kind of perceived motion blur range when using the particular screen without any bur reduction mode active.

The Contrast Ratio of a TFT is the difference between the darkest black and the brightest white it is able to display. This is really defined by the pixel structure and how effectively it can let light through and block light out from the backlight unit. As a rule of thumb, the higher the contrast ratio, the better. The depth of blacks and the brightness of the whites are better with a higher contrast ratio. This is also referred to as the static contrast ratio.

When considering a TFT monitor, a contrast ratio of 1000:1 is pretty standard nowadays for TN Film and IPS-type panels. VA-type panels can offer static contrast ratios of 3000:1 and above which are significantly higher than other competing panel technologies.

Some technologies boast the ability to dynamically control contrast (Dynamic Contrast Ratio – DCR) and offer much higher contrast ratios which are incredibly high (millions:1 for instance!). Be wary of these specs as they are dynamic only, and the technology is not always very useful in practice. Traditionally, TFT monitors were said to offer poor black depth, but with the extended use of VA panels, the improvements from IPS and TN Film technology, and new Dynamic Contrast Control technologies, we are seeing good improvements in this area. Black point is also tied in to contrast ratio. The lower the black point, the better, as this will ensure detail is not lost in dark image when trying to distinguish between different shades.

Brightness as a specification is a measure of the brightest white the TFT can display, and is more accurately referred to as its luminance. Typically TFT’s are far too bright for comfortable use, and the On Screen Display (OSD) is used to turn the brightness setting down. Brightness is measure in cd/m2 (candella per metre squared). Note that the recommended brightness setting for a TFT screen in normal lighting conditions is 120 cd/m2. Default brightness of screens out of the box is regularly much higher so you need to consider whether the monitor controls afford you a decent adjustment range and the ability to reduce the luminance to a comfortable level based on your ambient lighting conditions. Different uses may require different brightness settings as well so it is handy when reviews record the luminance range possible from the screen as you adjust the brightness control from 100 to 0%.

The colour depth of a TFT panel is related to how many colours it can produce and should not be confused with colour space (gamut). The more colours available, the better the colour range can potentially be. Colour reproduction is also different however as this related to how reliably produced the colours are compared with those desired.

At the lower end, TN Film panels are normally quite economical, and their sub pixels only have 64 possible orientations each, giving rise to a true colour depth of only 262,144 (i.e. 64 steps on each RGB = 64 x 64 x 64 = 18). This is also referred to commonly s 18-bit colour (i.e. 6 bits per RGB sub pixel = 6 + 6 + 6) This colour depth is pretty limited and so in order to reach 16 million colours and above, panel manufacturers commonly use two technologies: Dithering and Frame Rate Control (FRC). These terms are often interchanged, but strictly can mean different things. These technologies simulate other colours allowing the colour depth to improve to typically 16.2 million colours.

Spatial Dithering – The dithering method involves assigning appropriate colour values from the available colour palette to close-by pixels in such a way that it gives the impression of a new colour tone which otherwise could not have been created at all. In doing so, there complex mappings according to which the ground colours are mutually assigned, otherwise it could result in colour noise / dithering noise. Dithering can be used to allow 6-Bit panels, like TN Film, to show 16.2 million perceived colours. This can however sometimes be detectable to the user, and can result in chessboard like patterns being visible in some cases.

Frame Rate Control / Temporal Dithering– The other method is Frame-Rate-Control (FRC), also referred to sometimes as temporal dithering. This works by combining four colour frames as a sequence in time, resulting in perceived mixture. In basic terms, it involves flashing between two colour tones rapidly to give the impression of a third tone, not normally available in the palette. This allows a total of 16.2 reproducible million colours. Thanks to Frame-Rate-Control, TN panel monitors have come pretty close to matching the colours and image quality of VA or IPS panel technology, but there are a number of FRC algorithms which vary in their effectiveness. Sometimes, a twinkling artefact can be seen, particularly in darker shades, which is a side affect of such technologies. Some TN Film panels are now quoted as being 16.7 million colours, and this is down to new processes allowing these panels to offer a better colour depth compared with older TN panels.

Other panel technologies however can offer more possible pixel orientations and therefore more steps between each shade. VA and IPS panels are traditionally capable of 256 steps for each RGB sub pixel, allowing for a possible 16.7 million colours (true 8-bit, without FRC). These are referred to as 8-bit panels with 24-bit colour (8-bit per sub pixel = 8 + 8 + 8 = 24). While most IPS and VA panels support 8-bit colour, modern IPS and VA panels do sometimes use 6-bit + FRC instead. See this news piece for further information.

Colour gamut in TFT monitors refers to the range of colours the screen is capable of displaying, and how much of a given reference colour space it might be able to display. It is ultimately linked to backlight technology and not to the panel itself.

Laser Displays are capable of producing the biggest colour gamut for a system with three basic colours, but even a laser display cannot reproduce all the colours the human eye can see, although it is quite close to doing that. However, in today’s monitors, both CRT and LCD (except for some models I’ll discuss below), the spectrum of each of the basic colours is far from monochromatic. In the terms of the CIE diagram it means that the vertexes of the triangle are shifted from the border of the diagram towards its centre.

Traditionally, LCD monitors were capable of giving approximate coverage of the sRGB reference colour space as shown in the diagram above. This is defined by the backlighting used in these displays – Cold-cathode fluorescent lamps (CCFL) that are employed which emit radiation in the ultraviolet range which is transformed into white colour with the phosphors on the lamp’s walls. These backlight lamps shine through the LCD panel, and through the RGB sub-pixels which act as filters for each of the colours. Each filter cuts a portion of spectrum, corresponding to its pass-band, out of the lamp’s light. This portion must be as narrow as possible to achieve the largest colour gamut.

Traditional CCFL backlighting offers a gamut pretty much covering the sRGB colour space. However, the sRGB space is a little small to use as a reference in specifications for colour gamuts and so the larger NTSC colour space reference is also sometimes used. The sRGB space corresponds to approximately 72% of the NTSC colour space, which is a figure commonly used in specifications for standard CCFL backlit monitors. If you read the reviews here, you will see that analysis with colorimeter devices allows us to measure the colour gamut, and you can easily spot those screens utilising regular CCFL backlighting by the fact their gamut triangle is pretty much mapped to the reference sRGB triangle. The sRGB colour space is lacking most in green hues as compared with the gamut of the human eye. It should be noted that most content is produced based on the sRGB colour space, including Windows, many popular applications and internet content.

Above Right: a typical measurement of a monitor with enhanced CCFL backlighting, covering more than the sRGB colour space and about 92% of the NTSC space

To help develop and improve on the colour space a screen is capable of displaying a new generation CCFL backlighting was introduced. These so-called “wide gamut” backlights allow a gamut coverage of typically 92 – 102% of the NTSC colour space. There is a difference in practice which all users should be able to detect. The colour space available is extended mainly in green shades as you can see from the image above. Red coverage is also extended in some cases. This extended colour space sounds appealing on face value since the screens featuring WCG-CCFL backlighting can offer a broader range of colours. Manufacturers will often promote the colour space coverage of their screens with these high figures. In practice you need to consider what impact this would have on your use.

A compromise is sometimes available in the form of a screen which can support a range of colour spaces accurately. Some higher end screens come with a wide gamut backlight unit. Natively these offer a gamut covering 92 – 102% of the NTSC colour space. However, they also feature emulation modes which can simulate a smaller colour space. These emulation modes are normally available through the OSD menu and offer varying options with varying degrees of reliability. In the best cases the screens can emulate the smaller Adobe RGB colour space, and also the sRGB colour space. This allows the user to work in whichever colour space they prefer but gives them compatibility with a wider range of content if they have the need. The success of these colour space emulations will vary from one screen to another however and are not always accurate. Obviously you are still paying additional money for the wide gamut support, so if you’re only really interested in using sRGB mode then you’d probably be better looking for a standard gamut backlit screen.

LED backlighting has now become the norm for desktop monitors and is available in a few variations. The most common is White-LED (W-LED), which is a replacement for standard CCFL backlighting. The LED’s are placed in a line along the edge of the matrix, and the uniform brightness of the screen is ensured by a special design of the diffuser. The colour gamut is limited to sRGB as standard (around 68 – 72% NTSC) but the units are cheaper to manufacturer and so are being utilised in more and more screens, even in the more budget range. They do have their environmental benefits as they can be recycled, and they have a thinner profile making them popular in super-slim range models and notebook PC’s. It is possible to extend the colour gamut of W-LED displays using “Quantum Dot” technologies which are fairly new.

You will commonly see a monitor’s gamut listed as a percentage compared with a reference colour space. This will vary depending on which reference a manufacturer uses, but commonly you will see a % against the NTSC or Adobe RGB colour spaces. Bear in mind also that the gamut / colour space of the sRGB standard equates to about 72 – 75% of the NTSC reference. This is the standard colour space for the Windows operating system and the internet, and so where extended colour spaces are produced from a monitor, considerations need to be made as to the colour space of the content you are viewing.

Viewing angles are quoted in horizontal and vertical fields and often look like this in listed specifications: 170/160 (170° in horizontal viewing field, 160° in vertical). The angles are related to how the image looks as you move away from the central point of view, as it can become darker or lighter, and colours can become distorted as you move away from your central field of view. Because of the pixel orientation, the screen may not be viewable as clearly when looking at the screen from an angle, but viewing angles of TFT’s vary depending on the panel technology used.

On a CRT monitor, the refresh rate relates to how often the whole screen is refreshed by a cathode ray gun. This is fired down the screen at a certain speed which is determined by the vertical frequency set in your graphics card. If the refresh rate is too low, this can result in flickering of the screen and is often reported to lead to head aches and eye strain. On a CRT, a refresh rate of 72Hz is deemed to be “flicker free”, but generally, the higher the refresh rate the better.

TFT screens do not refresh in the same way as a CRT screen does, where the image is redrawn at a certain rate. As a TFT is a static image, and each pixel refreshes independently, setting the TFT at a common 60Hz native refresh rate does not cause the same problems as it would on a CRT. There is no cathode ray gun redrawing the image as a whole on a TFT. You will not get flicker, which is the main reason for having a high refresh rate on a CRT in the first place. Standard TFT monitors operate with a 60Hz recommended refresh rate, but can sometimes support up to 75Hz maximum (within the spec) or sometimes even further using ‘overclocking’ methods. The reason that 60Hz is recommended by all the manufacturers is that it is related to the vertical frequency that TFT panels run at. Some more detailed data sheets for the panels themselves clearly show that the operating vertical frequency is between about 56 and 64Hz, and that the panels ‘typically’ run at 60Hz (see the LG.Philips LM230W02 datasheet for instance – page 11). If you decide to run your refresh rate from your graphics card above the recommended 60Hz it will work fine, but the interface chip on the monitor will be in charge of scaling the frequency down to 60Hz anyway. Some screens will allow you to run at the maximum 75Hz as well for an additional boost in frame rates and some minor improvements in motion clarity. The support of this will really depend on the screen, your graphics card and the video connection being used. You may find the screen operates fine at the higher refresh rate setting but in reality the screen will often drop frames to meet the 60Hz recommended setting (or spec of the panel) anyway. Generally we would suggest sticking to 60Hz on standard TFT monitors.

The desire to offer higher frame rate support and higher refresh rates has lead to panel manufacturers developing panels which can natively support 120Hz+. It is common now to see 120Hz or 144Hz as natively supported refresh rates. This allows much higher frame rates to be displayed and the increase in refresh rate also brings about positive improvements in perceived motion clarity. TN Film panels have been around for many years now with high refresh rates and in recent years there has been development in IPS-type and VA-type panels to boost their refresh rates as well. You will also now see some ‘overclocked’ monitors available where manufacturers have attempted to boost the refresh rate further. For instance the native 144Hz IPS-type panel of the Asus ROG Swift PG279Q up to 165Hz, or the 144Hz native VA-type panel of the Acer Predator Z35 up to 200Hz. Results of these overclocks do vary and are not guaranteed but may provide some additional benefits.

You will see more mention of higher refresh rates from both LCD televisions and now desktop monitors. It’s important to understand the different technologies being used though and what constitutes a ‘real’ 120Hz and what is ‘interpolated’:

Interpolated 120Hz+– These technologies are the ones commonly used in LCD TV’s where TV signal input is limited to 50 / 60 Hz anyway (depending on PAL vs NTSC). To help overcome the issues relating to motion blur on such sets, manufacturers began to introduce a technology to artificially boost the frame rate of the screen. This is done by an internal processing within the hardware which adds an intermediate and interpolated (guessed / calculated) frame between each real frame, boosting from 50 / 60fps to 100 / 120 fps. This technology can offer a noticeable improvement in practice when it is controlled very well. Some sets even have 240 and 480Hz technologies which operate in the same way, but with further interpolation and inserted frames. See here for further information.

True 120HZ technology– to have a true 120Hz screen, it must be capable of accepting a full 120Hz signal output from a device (e.g. a graphics card). Because TV’s are limited at the moment by their input sources they tend to use the above interpolation technology, but with the advent of 3D TV and higher frequency input sources, this will change. Desktop monitors are a different matter though as graphics cards can obviously output a true 120Hz if you have a decent enough card. Some models can accept a 120Hz signal but need different interfaces to cope (e.g. dual-link DVI or DisplayPort).

Manufacturer specifications will usually list power consumption levels for the monitor which tell you the typical power usage you can expect from their model. This can help give you an idea of running costs, carbon footprint and electricity demands which are particularly important when you’re talking about multiple monitors or a large office environment. Power consumption of an LCD monitor is typically impacted by 3 areas:

Specs will often list a typical usage for the screen, normally related to whatever the default factory brightness control / luminance is. They may also list a maximum usage, when brightness is turned up to full and sometimes also an additional maximum when USB ports are in use. A standby power usage is often also included indicating the power draw when the screen is in standby mode. Some screens also feature various presets or modes designed to help limit power consumption, often just involving preset brightness settings. Again these can be useful in multi-monitor environments.

This relates to the connection type from the TFT to your PC or other external device. Older screens nearly all came with an analogue connection, commonly referred to as D-sub or VGA. This allows a connection from the VGA port on your graphics card, where the signal being produced from the graphics card is converted from a pure digital to an analogue signal. There are a number of algorithms implemented in TFT’s which have varying effectiveness in improving the image quality over a VGA connection. Some TFT’s with then offer a DVI input as well to allow you to make use of the DVI output from your graphics card which you might have. This will allow a pure digital connection which can sometimes offer an improved image quality. It is possible to get DVI – VGA converters. These will not offer any improvements over a standard analogue connection, as you are still going through a conversion from digital to analogue somewhere along the line. Dual-Link DVI is also sometimes used which is a single DVI connection but with more pins, allowing for higher resolution/refresh rate support than a single-link DVI.

With my Pi 3B attached to it, I see about 750 mA total power consumption (Pi + display) when the Pi is idling and not attached to anything else, and with a WiFi connection to a network but not transferring anything. You can use online Pi 3B and Pi 4 supply current consumption measurements done by others to extrapolate.

However, to actually start up the Pi 3B with the display, current bursts to beyond 1100mA need to be supported by the power supply for the Pi + display. And once the Pi is running applications then of course the overall current consumption of the Pi and Display can exceed that.

If you"re getting a power supply related issue you"ll need to use an "official" Pi power supply, because it outputs slightly higher voltage of 5.1V, not 5.0V, and has heavier gauge wire to reduce the voltage drop at times of high current demand.

If you"re running a high load from the Pi"s USB connectors or 40-way connector, then you may need to investigate other ways to power the peripherals independently. So, for instance, a USB keyboard or mouse would be fine, but a USB powered spinning drive might not - it"s experimental because there is no datasheet specifying the precise limit, it"s a low-end consumer product.

A wide variety of low power tft display options are available to you, You can also choose from original manufacturer, odm low power tft display,As well as from tft, ips, and tn.

IPS (In-Plane Switching) lcd is still a type of TFT LCD, IPS TFT is also called SFT LCD (supper fine tft ),different to regular tft in TN (Twisted Nematic) mode, theIPS LCD liquid crystal elements inside the tft lcd cell, they are arrayed in plane inside the lcd cell when power off, so the light can not transmit it via theIPS lcdwhen power off, When power on, the liquid crystal elements inside the IPS tft would switch in a small angle, then the light would go through the IPS lcd display, then the display on since light go through the IPS display, the switching angle is related to the input power, the switch angle is related to the input power value of IPS LCD, the more switch angle, the more light would transmit the IPS LCD, we call it negative display mode.

The regular tft lcd, it is a-si TN (Twisted Nematic) tft lcd, its liquid crystal elements are arrayed in vertical type, the light could transmit the regularTFT LCDwhen power off. When power on, the liquid crystal twist in some angle, then it block the light transmit the tft lcd, then make the display elements display on by this way, the liquid crystal twist angle is also related to the input power, the more twist angle, the more light would be blocked by the tft lcd, it is tft lcd working mode.

A TFT lcd display is vivid and colorful than a common monochrome lcd display. TFT refreshes more quickly response than a monochrome LCD display and shows motion more smoothly. TFT displays use more electricity in driving than monochrome LCD screens, so they not only cost more in the first place, but they are also more expensive to drive tft lcd screen.The two most common types of TFT LCDs are IPS and TN displays.

A thin-film-transistor liquid-crystal display (TFT LCD) is a variant of a liquid-crystal display that uses thin-film-transistor technologyactive matrix LCD, in contrast to passive matrix LCDs or simple, direct-driven (i.e. with segments directly connected to electronics outside the LCD) LCDs with a few segments.

In February 1957, John Wallmark of RCA filed a patent for a thin film MOSFET. Paul K. Weimer, also of RCA implemented Wallmark"s ideas and developed the thin-film transistor (TFT) in 1962, a type of MOSFET distinct from the standard bulk MOSFET. It was made with thin films of cadmium selenide and cadmium sulfide. The idea of a TFT-based liquid-crystal display (LCD) was conceived by Bernard Lechner of RCA Laboratories in 1968. In 1971, Lechner, F. J. Marlowe, E. O. Nester and J. Tults demonstrated a 2-by-18 matrix display driven by a hybrid circuit using the dynamic scattering mode of LCDs.T. Peter Brody, J. A. Asars and G. D. Dixon at Westinghouse Research Laboratories developed a CdSe (cadmium selenide) TFT, which they used to demonstrate the first CdSe thin-film-transistor liquid-crystal display (TFT LCD).active-matrix liquid-crystal display (AM LCD) using CdSe TFTs in 1974, and then Brody coined the term "active matrix" in 1975.high-resolution and high-quality electronic visual display devices use TFT-based active matrix displays.

The circuit layout process of a TFT-LCD is very similar to that of semiconductor products. However, rather than fabricating the transistors from silicon, that is formed into a crystalline silicon wafer, they are made from a thin film of amorphous silicon that is deposited on a glass panel. The silicon layer for TFT-LCDs is typically deposited using the PECVD process.

Polycrystalline silicon is sometimes used in displays requiring higher TFT performance. Examples include small high-resolution displays such as those found in projectors or viewfinders. Amorphous silicon-based TFTs are by far the most common, due to their lower production cost, whereas polycrystalline silicon TFTs are more costly and much more difficult to produce.

The twisted nematic display is one of the oldest and frequently cheapest kind of LCD display technologies available. TN displays benefit from fast pixel response times and less smearing than other LCD display technology, but suffer from poor color reproduction and limited viewing angles, especially in the vertical direction. Colors will shift, potentially to the point of completely inverting, when viewed at an angle that is not perpendicular to the display. Modern, high end consumer products have developed methods to overcome the technology"s shortcomings, such as RTC (Response Time Compensation / Overdrive) technologies. Modern TN displays can look significantly better than older TN displays from decades earlier, but overall TN has inferior viewing angles and poor color in comparison to other technology.

Most TN panels can represent colors using only six bits per RGB channel, or 18 bit in total, and are unable to display the 16.7 million color shades (24-bit truecolor) that are available using 24-bit color. Instead, these panels display interpolated 24-bit color using a dithering method that combines adjacent pixels to simulate the desired shade. They can also use a form of temporal dithering called Frame Rate Control (FRC), which cycles between different shades with each new frame to simulate an intermediate shade. Such 18 bit panels with dithering are sometimes advertised as having "16.2 million colors". These color simulation methods are noticeable to many people and highly bothersome to some.gamut (often referred to as a percentage of the NTSC 1953 color gamut) are also due to backlighting technology. It is not uncommon for older displays to range from 10% to 26% of the NTSC color gamut, whereas other kind of displays, utilizing more complicated CCFL or LED phosphor formulations or RGB LED backlights, may extend past 100% of the NTSC color gamut, a difference quite perceivable by the human eye.

The transmittance of a pixel of an LCD panel typically does not change linearly with the applied voltage,sRGB standard for computer monitors requires a specific nonlinear dependence of the amount of emitted light as a function of the RGB value.

In 2004, Hydis Technologies Co., Ltd licensed its AFFS patent to Japan"s Hitachi Displays. Hitachi is using AFFS to manufacture high end panels in their product line. In 2006, Hydis also licensed its AFFS to Sanyo Epson Imaging Devices Corporation.

Less expensive PVA panels often use dithering and FRC, whereas super-PVA (S-PVA) panels all use at least 8 bits per color component and do not use color simulation methods.BRAVIA LCD TVs offer 10-bit and xvYCC color support, for example, the Bravia X4500 series. S-PVA also offers fast response times using modern RTC technologies.

A technology developed by Samsung is Super PLS, which bears similarities to IPS panels, has wider viewing angles, better image quality, increased brightness, and lower production costs. PLS technology debuted in the PC display market with the release of the Samsung S27A850 and S24A850 monitors in September 2011.

TFT dual-transistor pixel or cell technology is a reflective-display technology for use in very-low-power-consumption applications such as electronic shelf labels (ESL), digital watches, or metering. DTP involves adding a secondary transistor gate in the single TFT cell to maintain the display of a pixel during a period of 1s without loss of image or without degrading the TFT transistors over time. By slowing the refresh rate of the standard frequency from 60 Hz to 1 Hz, DTP claims to increase the power efficiency by multiple orders of magnitude.

Due to the very high cost of building TFT factories, there are few major OEM panel vendors for large display panels. The glass panel suppliers are as follows:

External consumer display devices like a TFT LCD feature one or more analog VGA, DVI, HDMI, or DisplayPort interface, with many featuring a selection of these interfaces. Inside external display devices there is a controller board that will convert the video signal using color mapping and image scaling usually employing the discrete cosine transform (DCT) in order to convert any video source like CVBS, VGA, DVI, HDMI, etc. into digital RGB at the native resolution of the display panel. In a laptop the graphics chip will directly produce a signal suitable for connection to the built-in TFT display. A control mechanism for the backlight is usually included on the same controller board.

The low level interface of STN, DSTN, or TFT display panels use either single ended TTL 5 V signal for older displays or TTL 3.3 V for slightly newer displays that transmits the pixel clock, horizontal sync, vertical sync, digital red, digital green, digital blue in parallel. Some models (for example the AT070TN92) also feature input/display enable, horizontal scan direction and vertical scan direction signals.

New and large (>15") TFT displays often use LVDS signaling that transmits the same contents as the parallel interface (Hsync, Vsync, RGB) but will put control and RGB bits into a number of serial transmission lines synchronized to a clock whose rate is equal to the pixel rate. LVDS transmits seven bits per clock per data line, with six bits being data and one bit used to signal if the other six bits need to be inverted in order to maintain DC balance. Low-cost TFT displays often have three data lines and therefore only directly support 18 bits per pixel. Upscale displays have four or five data lines to support 24 bits per pixel (truecolor) or 30 bits per pixel respectively. Panel manufacturers are slowly replacing LVDS with Internal DisplayPort and Embedded DisplayPort, which allow sixfold reduction of the number of differential pairs.

Kawamoto, H. (2012). "The Inventors of TFT Active-Matrix LCD Receive the 2011 IEEE Nishizawa Medal". Journal of Display Technology. 8 (1): 3–4. Bibcode:2012JDisT...8....3K. doi:10.1109/JDT.2011.2177740. ISSN 1551-319X.

Brody, T. Peter; Asars, J. A.; Dixon, G. D. (November 1973). "A 6 × 6 inch 20 lines-per-inch liquid-crystal display panel". 20 (11): 995–1001. Bibcode:1973ITED...20..995B. doi:10.1109/T-ED.1973.17780. ISSN 0018-9383.

Richard Ahrons (2012). "Industrial Research in Microcircuitry at RCA: The Early Years, 1953–1963". 12 (1). IEEE Annals of the History of Computing: 60–73. Cite journal requires |journal= (help)

K. H. Lee; H. Y. Kim; K. H. Park; S. J. Jang; I. C. Park & J. Y. Lee (June 2006). "A Novel Outdoor Readability of Portable TFT-LCD with AFFS Technology". SID Symposium Digest of Technical Papers. AIP. 37 (1): 1079–82. doi:10.1889/1.2433159. S2CID 129569963.

Kim, Sae-Bom; Kim, Woong-Ki; Chounlamany, Vanseng; Seo, Jaehwan; Yoo, Jisu; Jo, Hun-Je; Jung, Jinho (15 August 2012). "Identification of multi-level toxicity of liquid crystal display wastewater toward Daphnia magna and Moina macrocopa". Journal of Hazardous Materials. Seoul, Korea; Laos, Lao. 227–228: 327–333. doi:10.1016/j.jhazmat.2012.05.059. PMID 22677053.

I bought the display along with the camera board v2 a couple of months ago to work on some projects with my Raspberry Pi 2 but only recently found the time to actively experiment. Now unlike the camera board where there is actual official entry in the FAQ for the Raspberry Pi (see here) I seem to be unable to find any for the official 7" display especially in terms of power consumption though there are plenty of blog posts that discuss the topic.

My power supply (5V/2A...hopefully) is not the official one. It came with the Raspberry Pi kit I bought (plus casing, fan, heat sinks, SD card (a very crappy one from Intenso; had to buy a new one since it got corrupted pretty fast) etc.). I have noticed the following:

Active Ethernet connection (a single SSH session running between by notebook and Raspbian) + attached display (power goes through it to the Pi) - I sometimes get the colourful square depending on what I do software-wise which indicates power issues. Touch on the screen works

I would like to combine both the display, Ethernet connection and the camera board and I would like to know what the power consumption would be in such a scenario. Any ideas?

The Pi 2 requires approx. 1.8A, the camera on the other hand requires 250mA which would make the 5V/2A power supply enough for the two to run withou