Thesaurus for LED technology
Terminology used for Virtual Production, xR, and Film
New technology often comes with a new set of terminology. To guide your way into the what-is-what of LED technology for virtual production we have complied this easy and no-nonsense thesaurus. Read it below or download it here:
Picture by: MMC Studios
Live LED wall
A live LED wall is any LED wall used for virtual production where the content is displayed during the camera shoots.
LED display resolution
The number of distinct pixels in the respective dimension that can be displayed, generally mentioned as pixel per width × height, is the LED display resolution.
Pixel pitch is the distance from the center of an LED cluster (or pixel) to the center of the next LED cluster/pixel measured in millimeters. This is not necessarily the same as the pixel size, which refers to the size of an individual pixel. The shorter the viewing distance (closer shooting distance) the smaller pixel pitch is required.
The driver IC will control the LED. It will generate the PWM signals to have the LEDs display the required brightness. The modern driver IC’s use many advanced technologies to get the best possible performance out of the LED.
The receiver card is the link between the LED processor (with video input) and the driver ICs (connected to the LEDs, video output). Except for decoding and distributing the video signal, the Receiver card will do a lot of extra corrections, such as brightness, gamma, calibration, etc.
Color gamut is “the color triangle”. The larger the surface you can cover in this triangle with your LED panel, the more colors you can show.
Refresh rate is how many times per second a frame is redrawn on the display. (Typically, 1920, 3840, 7680Hz)
Scan rate, also named scan mux or multiplexing. One driver IC output pin drives multiple LEDs. This is done by completing the circuit for each LED one by one (multiplexing). During one refresh cycle, all the LEDs will light up once. Typical scan rates are 16:1, 11:1, 8:1
Contrast is the difference in luminance or color that makes an object (or its representation in an image or display) distinguishable.
Frame rate is the number of frames per second. This is typically determined by the video source. (Typically, 24, 50, 60Hz)
Scan lines is the effect your eyes or the camera pick up when the refresh rate is too low. A camera is more sensitive than our eyes to pick up scanlines. Typically higher refresh rates are desirable and genlocking (synching) the refresh rates between the screen and camera may be needed.
Flip-Chip LEDs are more energy-efficient LEDs. The new flip-chip technology lowers costs and energy consumption. It creates a darker black and gives more brightness on lower current. With respect to color shift it might have a lesser performance, something to be aware of.
COB - Chip on Board
COB technology is a method to package the LED chip directly on the module.
GOB - Glue on Board
GOB Technology is an innovative method to seal the LED packages on the module surface with epoxy glue.
The moiré patterns or moiré fringes are large-scale interference patterns. For the moiré interference pattern to appear, two patterns must not be completely identical, but rather displaced, rotated, or have a slightly different pitch, like between camera and LED screen.
A special mask fitted to the LED panel or LEDs on the panel reduces the moiré-effect.
The angle at which a display can be viewed with acceptable visual performance. In other words, the luminous intensity measured at right angles to the surface of the LED chip, a measure of the position where the intensity of the LED light spread reaches 50% of its maximum brightness. The illumination continues past the edge of the viewing angle but continues to decrease in intensity.
Ghosting on LED screens is an image artifact where pixels will light up with neighboring pixels when they are not supposed to be lighting up. In general, it is caused by an undesired current, mostly introduced by the parasitic capacitance, that will light up the neighboring pixels.
Brightness is expressed in nits. A nit is a unit of measurement of luminance, or the intensity of visible light, where one nit is equal to one candela per square meter (CD/M2). The higher number of nits, the brighter the screen.
Video or image jitter occurs when the horizontal lines of video image frames are randomly displaced due to the corruption of synchronization signals or electromagnetic interference during video transmission. Jitter can cause a display monitor to flicker.
Color banding is a problem of inaccurate color presentation in graphics and is related to the bit-depth.
Reflection is the mirroring effect of light on surfaces (like an LED).
The shift in color when looking at the LED screen under an angle, is due to the placement of the LED diodes (red, green, blue) in the LED package.
High-dynamic-range video (HDR video) is video having a dynamic range greater than that of standard-dynamic-range video (SDR video). HDR video involves capture, production, content/encoding, and display. HDR displays are capable of brighter whites and deeper blacks. To accommodate this, HDR encoding standards allow for a higher maximum luminance and use at least a 10-bit dynamic range in order to maintain precision across this extended range. While technically “HDR” refers strictly to the ratio between the maximum and minimum luminance, the term “HDR video” is commonly understood to imply wide color gamut as well.
Bit Depth, aka Color Depth, describes the amount of information stored in each pixel of data. As you increase bit depth, you also increase the number of colors that can be represented. In the case of an 8-bit image, each pixel has 8-bits of data per color (RGB), so for each color channel the pixel has 28 = 256 possible variations. 10-bit would give 210 = 1024 color variations and 12-bit 212 = 4096.
IMD (Integrated Mounted Devices) technology (N-in-1) integrates two, four or six sets of RGB lamp beads into one small unit.
Common anode vs Common cathode
Common anode means that the anode (positive) side of all of the LEDs is electrically connected at one pin, and each LED cathode has its own pin. Common cathode means that the cathodes of all of the LEDs are common and connected to a single pin. The anode for each LED has its own pin. Common cathode will save power consumption (up to 30%), will decrease the screen temperature (up to 25%) and will make electronic components more reliable at relatively low temperatures, resulting in a longer life span.
Genlocks, generator locking, is the technique that is used to synchronize video signals, coming out of a signal generator or similar source, to the other picture resources. Genlock technology is widely used in video applications. One of the most common genlock applications is to synchronize cameras. Genlock is used to sync video signal or pixels to an external synchronization source, while synchronizing the SDI output to an external source, the SDI refresh rate is determined with the help of a sync source.
(Read more on genlock)
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