Buying Guide of LED Display (Part A)

Tag: outdoor full-color LED billboards, purchase LED display screen, LED display board buying guide

What kind of factors should be take into consideration when buying a LED display screen? If you want to know more information, VERYPIXEL here to help you fix these questions.


outdoor full-color LED billboards


Considering the factors of screen area that users site as follow: 
a. Relationship between the effective sight distance and actual spot size.
b. Pixel dimensions and resolution.
c. Unit as the base of area estimation.
d. Screen mechanical installation and maintenance of operating space
e. The screen dip angle has impacts on the distance.


What kind of display effect does the users need ?
a. Text display: according to the size and resolution of the screen.
b. Ordinary video display: 320 x 240 dot matrix.
c. Digital standard DVD display: ≥640 × 480 dot matrix
d. Complete Computer Video: ≥800 × 600 dot matrix


Requires of the screen brightness as to ambient brightness
a. Indoor: >800CD/M2
b. Semi-indoor: >2000CD/M2
c. Outdoor(Northward) :>4000CD/M2
d. Outdoor(Southward):>8000CD/M2

What kind of brightness requirements in the composition of white color for red, green, blue LEDs?
Red , green and blue color LEDs have great impact in terms of white coupler. The fundamental
reason is because the retina of the human eye have different feelings for different wavelengths of
light. After a number of experimental tests, we get the following data for your references:

A. Simple red, green and blue color brightness ratio is 3 : 6 : 1;
B. Accurate red, green and blue color brightness ratio is 3.0:5.9:1.1

Why a high-end full-color display use pure green tube ?

In practical LED display production, we should choose high luminous efficiency and rich bright coloration rendering tricolor LED lamps in order to make the chromaticity diagram color triangle area as close as possible in the tongue-shaped spectral color curve, to meet the rich color and produce enough brightness and tongue shaped curve top for the 515nm wavelength of light, so the high-grade LED display selected wavelengths close to 515nm pure green light LED tube, LED tube such as selection of 520nm, 525nm or 530nm wavelengths of light.


In the condition of knowing brightness and pixel density requirements,how can we calculate the brightness of single- tube computer ?

Calculation Method as follow: (for example : 2 red, 1 green and 1 blue LED)
Red LED brightness: Brightness (CD)/㎡ ÷ dots/㎡×0.3÷2
Green LED brightness: Brightness (CD)/㎡ ÷ dots/㎡×0.6
Blue LED brightness: Brightness (CD)/㎡ ÷ dots/㎡×0.1
For example: the dot density is 2,500/㎡and brightness is 5,000CD/㎡, thus:
Red LED brightness: 5000÷2500×0.3÷2=0.3?
Green LED brightness: 5000÷2500×0.6÷2=1.2
Blue LED brightness:  5000÷2500×0.1=0.2
So every single pixel brightness is : 0.3×2+1.2+0.2=2.0 CD


Why use DVI display interface standard ?
a. DVI display card interface is a kind of interface that in line with international standards of Computer
b. No need to open the chassis and easy to install
c. High memory, strong ability to show dynamic picture
d. Good in Hardware and software compatibility
e. Supports all operating systems and application software
f.Mass production, low cost, easy maintenance


Why can not use a laptop to control an LED display?
The display card was built in laptop, which makes it can not connect with contoling system. currently have a laptop now with DVI interface enables notebook control.


What different between Nichia chips and Homemade chips except price for a full color LED
1. Chips: Nichia products their own chips while domestic manufacturers mainly use U.S. or
Taiwanese company’s chips instead.
2. Package: Nichia has their own packaging technology, but China has many packing factories
barely has production plant
3. Conformity: Nichia chips have smaller wavelength difference in same batch,therefore have a
better conformity than domestic LED chips.
4. Life Span: Nichia chips have longer life span than domestic manufactured chips.


outdoor full-color LED billboards


What is the difference between full color indoor module and full color SMD screen?
a. Light-emitting part: the matrix full color LED display are olivine color because pure green LED lamps are more expensive. However, SMD full color LED display mainly use pure green LEDs.
b. Display effect: the matrix LED display has bad visual sense, low brightness and easy to have mosaic. But SMD LED module have good conformity and higher brightness.
c. Maintenance: it is hard to maintain a matrix full color LED module and it costs too much when change the entire modules. While full color SMD are more easy to maintain available to single lamp repair and replacement.


Why outdoor LED display can not adopt SMD LEDs?
Outdoor LED screen installation structures have strictly demands that is the SMD modules can not
adapt to the harsh outdoor environment. It requires high brightness.


Why outdoor LED display needs longer production time?
1. Raw materials purchasing: LED lamps purchasing requires a longer time to fulfill especially for import LED chips. The order cycle are going to take 4-6 weeks.
2. Complex production process: Subject to PCB design, production casing , plastic irrigation, adjusting white balance, etc.
3. Strict structural requirements: cabinet design requires Wind, rain, lightning protection etc.


Related articles: Buying Guide of LED Display (Part B)

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