Frequently Asked Questions about Led Screens


1. WHAT IS VARIABLE MESSAGE SIGN OR VMS?

LED Displays, Digital Signage, Dynamic Displays, Electronic Billboards are all different names for the VMS (Variable Message Signs). VMS are generally used to broadcast visual communications (messages) consisting of text, graphics, video and/or audio.

2. HOW MUCH DOES A LED GIANT SCREEN COSTS?

The final cost of a LED screen depends on two main factors:
 - The resolution (meaning the total number of LEDs present on each square meter)
 - The size of the screen (meaning the number of square meters needed to create the screen)
Because these factors are depending on the customer's needs, it is impossible to determine in advance the cost of a LED screen.

3. WHAT IS A LED?

LED is the acronym of Light Emitting Diode and it is a semiconductor that emits visible light when electricity passes through it. The emission of light depends on electrons flowing between anode and cathode and the color of the visual emission (that can be Red, Green, Blue, Amber, and White...) depends on the material utilized.

4. WHAT IS A PIXEL?

By definition, the pixel is the "luminous dot" present on every LED device, from the simple alphanumerical Single Line display to Full Color screens. This luminous dot can be formed by 1 or more LEDs depending on dimensions and features of the device. For example, on a small-size Single Line display, the pixel is formed by 1 single LED while on the king-size model the pixel can be formed by 20 LEDs. In some products, the pixel can be composed by up to 36 LEDs. 

5. WHAT IS THE PITCH (OR "DOT PITCH" OR "PIXEL PITCH")?

The pitch of a LED display defines the distance between the pixels, expressed in millimeters. This fundamental measure determines the characteristics and the performances of a LED screens: the pitch indeed is a defining factor of a screen's viewing distance: #1 - The smaller is the pitch, the shorter is the minimum viewing distance, the higher is the total number of pixels present on the screen (and therefore higher is the screen's cost per area). #2 - The bigger the pitch is, the longer the minimum viewing distance will be, the lower  the total number of pixels present on the screen (and therefore the screen's cost per area will be lower) The pixel pitch therefore determines the LEDs density, which is usually called Resolution. It is important to notice that while reducing the pixel pitch, the LED density increase exponentially: for example, reducing the pitch by the 50% on the number of pixels grow of 4 times.
 

6. WHAT IS THE DIFFERENCE BETWEEN SMD AND PTH LEDS?

SMD is the acronym of Surface Mounting Device and it is the new frontier of the electronic visualization technology: the revolution created by the SMD technology is represented by the miniaturization of all the electronic components, LEDs included. The SMD components are mounted on the surface of the electronic board, without passing through it as any other electronic component utilizing the former technology, called PHT (acronym of Plating through Holes? The SMD TOP LED is therefore mounted on the external part of the board (without the anode and cathode passing through holes), as described in the image below (proportions are real): LEDs utilizing the SMD technology are different from the PHT LEDs for another important characteristic: thanks to the miniaturization indeed it is possible to put 3 LEDs of different colors within the same case , resulting in a three colors LED. The possibility to visualize three colors at the same time (Red, Green and Blue) on a single LED allow us to create screens with an even smaller pitch (the distance between pixels) therefore resulting in a higher resolution and quality image.
 

7. WHAT IS THE RESOLUTION OF A DISPLAY?

The resolution is nothing else but the number of pixels present on each square meter. The resolution is therefore opposite proportional to the pixel pitch: the smaller the distance between two pixels, the higher the resolution (because on the surface of the screen is present an higher number of LEDs). For example a 20 mm pitch screen has a resolution of 2304 pixels: this measure is obtained dividing the total length of a single module (975 mm) by the pixel pitch (in this case 20 mm) resulting in the number of pixels on a single line: 975:20 = 48 pixels. Multiplying the number of pixels present on a single line by the total number of lines the result is the total number of pixels present on the screen surface, also called Resolution. In our example, 48 x 48 = 2304 pixel in total. Given this formula, it is possible to calculate that a 30 mm pitch screen has a resolution of 1024 pixel per module, while a 10 mm pitch screen has a resolution of 9216 pixels per module. It is important to notice that reducing only a few millimeters the pixel pitch, the LED density (and therefore the resolution) increase exponentially.

Remember: The smaller the pitch - the shorter is the minimum viewing distance. The higher the total number of pixels present on the screen is - the higher is the quality image

8. WHAT IS THE DEFINITION OF A DISPLAY?

The "definition" is the number of vertical and horizontal pixels that are on the entire screen. For example, some standard definitions are 96x64 pixels (=low definition); 256x192 pixels (=medium definition): 640x480 pixels (=high definition). The definition is therefore related to the pixel pitch, the distance between the pixels. To simplify and clarify the terminology, it is possible to say that the RESOLUTION is referred to the single module, while the DEFINITION is referred to the entire screen, once that all modules have been mounted.

9. WHAT'S THE DIFFERENCE AMONG SCREENS WITH THE SAME DIMENSIONS BUT WITH A DIFFERENT PITCH?

The difference is the optimal viewing distance. The LED screen with an higher definition (therefore a the smaller pitch and a greater number of LEDs per m2) has an higher image quality, ideal even for short viewing distance. The screen with a lower definition (therefore with a bigger pitch and a smaller number of LEDs per m2) has a lower image quality, ideal for greater viewing distance. It is important to clarify that the definition is determined by the screen viewing distance once it will be installed: if a screen will be observed from 300 meters, it doesn't need an high definition because of a biological reason: the human eye cannot discriminate small details from larger distances anyway. On the other side, a screen observed from 30 meters needs a higher definition because from such a short distance the human eye is able to recognize even small details. To provide a comparison, in the table below are represented two hypothetical screens of the same dimensions but with different definition: the first (fig. 1) has a higher definition and is therefore ideal even for short viewing distances. The second one (fig. 2) has a lower definition and it is ideal for greater viewing distances. To better understand the viewing distance concept, please look at the pictures from few centimeters and then from 3 meters: even if the images have a different definition, if observed from 3 meters distance, they seem to have the same quality.

 

10. WHAT ARE THE MINIMUM AND MAXIMUM VIEWING DISTANCES OF A LED SCREEN?

The minimum and maximum viewing distances of a LED screen are measured depending on two fundamental characteristics of the screen: the pixel pitch and the screen's dimension. #1 - the minimum distance is calculated converting into meters the pixel pitch. For example, a maxi screen with 10mm pitch has a minimum viewing distance of 10 meters, while a 20mm pitch screen has a minimum viewing distance of 20 meters. #2 - the maximum distance instead, depends on the screen's dimension and it can be calculated multiplying x10 and converting into meters the number of maxi-screen's square meters. For example a 4x3 meters (=12sq) can be viewed from 120 meters distance. While talking about maximum distance, there are two concepts to clarify, "readability" and "visibility". "Readability" identifies the distance within the images broadcasted on the maxi screen are readable, thus clearly recognizable. "Visibility" identifies the distance within the images showed are able to attract the human eye's attention, even if the images are not perfectly identifiable. The visibility of a maxi-screen is usually the double of its readability (in our former example: readability 120 meters = visibility 240 meters). Regarding the written texts, the readability depends on the fonts' size. Generally, it is possible to say that every centimeter can be read from about 5-meter distance. For example, 10 cms texts can be read from about 50 meters. 

11. IS IT POSSIBLE TO DISPLAY A VIDEO ON THE LED SCREENS?

Of course yes. LED Screens have their main application field in the live video visualization during concerts, sports events and TV shows. For the video visualization it is important to be aware of the fact that, to obtain a satisfactory quality of the images, it is necessary to utilize a display with a minimum resolution of 192 x 128 pixels. Power Screens graphic screens function as huge monitors and they are able to visualize in real-time anything that is visualized on the PC monitor, a DVD or a live performance. 

12. WHAT IS THE 16 BIT TECHNOLOGY?

Displays utilizing an 8 bit technology, that degrades the image during the video elaboration phase, are able to visualize 256 color levels for each of the three primary colors. This means that you are able to visualize 256 x 256 x 256 = 16, 8 millions colors in total. Our screens instead utilize a 16 bit technology for each color that allows us to manage the video without altering the quality in a perceptible way (so the human eye does not notice it). After this elaboration (called Gamma Correction) it is possible to visualize 65.000 color levels for each of the three primary colors. This means that it is possible to visualize 65.000 x 65.000 x 65.000 = 280 trillion colors in total.
 

13. WHAT ARE THE COLOR'S TEMPERATURE AND WHY IS IT IMPORTANT?

As an international convention defined by the CIE (International Commission of Illumination) states, while evaluating the properties of any source of light, it is used a measure that it takes into account their chromatic content. Such measure of reference is called "color's temperature" and it is expressed in Kelvin degrees (°K). Low levels of color's temperature correspond to color's tones stretching out to the red, while high levels correspond to color's tones stretching out to the blue. In LED screens it is fundamental to keep constant this measure to visualize high quality and naturalness pictures. Power Screens, screens are provided with an electronic system of colors' equalization that manages these parameters automatically, depending on the environmental brightness, in order to obtain a constant color temperature both in daylight and at night.

14. WHY IS THE PURE WHITE CREATED WITH THREE LEDS OF DIFFERENT COLORS?

Because the human eye has three types of receptors for the vision during the day and each one of them correspond to a primary color. Any other color is the result of the simultaneous stimulation of these three types of receptors, after a phenomenon called addition synthesis (that mix the chromatic components captured by the eye). The mix of the three primary colors, in different percentages, therefore generates each color. The color of reference, the pure white, is obtainable mixing the primary colors in the percentage of about 50% green, 30% red and 20% blue. Power Screens technology allows, varying these values, to obtain 280 billion colors. This huge palette is a guarantee of a superior image quality and unbeatable visualization capacity.

 

15. WHAT IS THE VISIBILITY ANGLE?

The visibility angle of a screen is by convention the angle within which the brightness of a display is equal to the 50% of the frontal luminosity. For example, a screen with 5000 NIT frontal luminosity (NIT = millicandels/sq) has a visibility angle equal to the angle by which the brightness is reduced to 2500 NIT. This visibility angle can vary depending on the LED and the technical features of the display.
 

16. WHAT IS THE VIRTUAL PIXEL TECHNOLOGY?

The Virtual Pixel is a technology of image management that allows visualizing pictures of a definition higher than the physical one, thanks to a technique called "pixel interpolation". Power Screens Virtual Pixel technology is able to control every single LED: this particular and exclusive screen management feature allows overlying every single pixel to the next one, creating a so-called "virtual pixel" (a pixel that does not exist but is perceptible by the human eye). The screen's definition is one of the characteristics that define images' quality and naturalness: the higher the resolution, the higher the picture's quality will be. Power Screens -screens with virtual pixel technology can visualize images with a definition four times higher than the physical definition of the display; therefore, images are more detailed and realistic.

17. WHAT IS THE REFRESH RATE AND WHY IS IT IMPORTANT?

The refresh rate indicates the number of times that the image refreshes every second. For example, a PC monitor has a refresh rate of 72 Hertz (Hz) and therefore refresh all the pixels of the screen, from top to bottom, 72 times every second. The refresh rate is fundamental because it determines the image's quality: if it is too low, the human eye can see a flicker that causes headaches and can damage eyes. To provide a comparison, most of the TV monitors have a refresh rate of 50Hz and only few products of the last generation have a 100Hz refresh rate. Power Screens - screens have a 300 Hz refresh rate, which is almost triple of the most advanced cathode tube technologies. This measure is ulterior prove of Power Screens quality and state-of-the-art technology, a result of years of research in laboratories and in the field. 

18. WHAT IS THE CONTRAST LEVEL?

It is the difference between the light emitted by the display and the environmental light reflected by the screen surface. The lower the light reflected, the higher the contrast and therefore the cleanliness and naturalness of the images. To increase the contrast, we provided solutions with particular anti-reflex flyers that split the light and reflect it in different directions, increasing the visibility of the screen even in direct sunlight. 

19. WHAT IS THE MODULAR SYSTEM?

It is a system that allows building LED screens of big dimensions mounting together several base-modules, depending on the customer's specific needs. Our base modules have different sizes, depending on the application (proEVENT®, proMARKET®, proGAME® or proTRUCK®). These modules are fixed together with a Dual-Lock systems and the perfect alignment of the pixels is guaranteed by an auto-centering system that avoids the awful conjunction lines. Our modular system offers huge advantages: it allows an easy transportation and a simple mounting procedure; it permits an easy maintenance, doesn't put any limit in shape, size and resolution and moreover allows the future upgradeability of the screen.