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how to choose a LED screen especially the flexible led curtain display?
2010-09-08 17:26:56

the advice on how to choose led video wall for your multimedia video, vision and lighting application

Replied by Fisher:
I have been serving as a sales for led screen especially flexible led curtain display for more than 5 years, maybe I can give you some suggestion to help you choose the correct product for your multimedia video, vision and lighting wall. 
Brightness of LED Screen wall: 
Luminance (brightness) is a photometric measure of the luminous intensity per unit area of light travelling in a given direction. It describes the amount of light that passes through or is emitted from a particular area, and falls within a given solid angle. The SI unit for luminance is candela per square metre (cd/m2). A non-SI term for the same unit is the "nit". The CGS unit of luminance is the stilb, which is equal to one candela per square centimetre or 10 kcd/m2.
Luminance is often used to characterize emission or reflection from flat, diffuse surfaces. The luminance indicates how much luminous power will be detected by an eye looking at the surface from a particular angle of view. Luminance is thus an indicator of how bright the surface will appear. In this case, the solid angle of interest is the solid angle subtended by the eye's pupil. Luminance is used in the video industry to characterize the brightness of displays. A typical computer display emits between 50 and 300 cd/m2. The sun has luminance of about 1.6×109 cd/m2 at noon.[1]
Luminance is invariant in geometric optics. This means that for an ideal optical system, the luminance at the output is the same as the input luminance. For real, passive, optical systems, the output luminance is at most equal to the input. As an example, if you form a demagnified image with a lens, the luminous power is concentrated into a smaller area, meaning that the illuminance is higher at the image. The light at the image plane, however, fills a larger solid angle so the luminance comes out to be the same assuming there is no loss at the lens. The image can never be "brighter" than the source.
For LED screen, the brightness of the LED lamp, the density of LED lamp (pitch size) and the scan model (driving model) determine the brightness.
( how to calculate the brightness of the led screen)
Usually if we are going to use the led screen indoor or at night, we can choose the led screen with about 1000 CD (nits), if we are going to use the led screen outdoor under the sunbeam, we need the led screen with brightness larger than 5500 nits.
If we are going to use the led screen semi outdoor or at shadow place where the sunbeam cannot project directly, we can choose the led screen with about 2000 to 4000 nits.
Usually we calculate the brightness when the led screen show white color, so it the maximum brightness of the led screen. When the led screen is playing video, so the brightness is changeable, because during some time, the status of each color is different, so the brightness is difference. 
The pixel number (pixel density):
We need pixel to show the led screen, the image quantity largely depend on the resolution, so we need some pixel quantity to show image. 
Usually we need a screen with more than 45000 pixel to show image, the more the better. If you want to show HD video, we need enough pixels.
If you want to show 1080P image without compress, you need a screen with 1920×1080 pixels, otherwise we have to compress the original video into proper size that fit the resolution of the led screen, if we do not compress the original video, the led screen just show partial of video.
For example, your led screen is 256 x 320 pixels, but your video source is 480 x 640 pixels, so we have to compress the original video into 256x320 pixels. Because the viewing distance is long, we can get good image quality with 256x320 (81920) pixels.
It is impossible to show clear image on a LED screen with P20 2x3m, because the pixel number is only 100x150 pixels.
Certainly if you just want to show some visual effect, some letter or the simple video, so you can choose a LED screen with less than 40000 pixels.
The LED screen is only a screen, it is controlled by PC or DVI video source. If we use PC to control the led screen, we have to set the led screen copy (clone or duplicate ) the PC screen (your PC monitor),usually the resolution of led screen is 768x1024 pixels, if the resolution of LED screen is 256x320, so it just show (copy /clone / duplicate) the part of 256x320.
If we want to show clear image with small screen and short viewing distance, we need high resolution screen, for example pitch 6mm led screen, if the size is 2x3 m, so there are 330x500 pixels, you can get good image from three meters away.
Protection level:
If we are going to use the led screen indoor, we do not need the led screen with waterproof, but we also need to think about the dust, and we need to think about the tiny metal, there is not any problem with the body of led screen, because the body just works with DC 5 V or 24V power, so it is not dangerous; but we need to think about the power switcher, because the input of the power is from AC100 to 240V, we need to protect people from touching it, and we also need to think about the tiny metal to destroy the power switcher. The power box we provided is IP65, it is protected from water and dusk from all direction.
If we are going to install the led screen outdoor permanently, we need to choose led screen with at least IP65, what’s more, we need to think of the weathering, with long term sunshine (ultra violet), strong wind and rain (impure water, or acid rain), we need to protect the whole device especially the LED lamp, because the LED lamp is keyman that determine the longevity (life time) of the whole screen.
the info above is provided and edited by Fisher Dakota personally, if there is  any discrepancy, please contact:
mail/MSN: yuchao622@hotmail.com
skype: fisher201223
tel: 0086-186 8033 9086
new video flexible LED curtain
HF-P10 http://youtu.be/oFU49fyCi1g
F-P12 http://youtu.be/VITqfm_0a2k
F-P20 http://youtu.be/A_ZuP2jh6MI
LC-P20 http://youtu.be/eCq96DlBsIw
LC-P50 http://youtu.be/Vcai3GUmqB8
S-P20 http://youtu.be/Ih0ljyrNWy4  
S-P30 http://youtu.be/2LMAEwdd3uA
S-P50 http://youtu.be/zh6WyyTYbXU

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