4.从上图不能看出来勒克斯，是一个不正确的单位，从勒克斯也不能转换成其它单位,可以由pi（π）和m2/ft2（0.0929）导出下面关系：例如nits与fL转换的公式为：1 nits×0.2919=1 fL；1 fL×3.426=1 nits
[注；这些因数由pi（π）和 m2/ft2（0.0929）导出。
1 Lux = 1 lm per square meter = 0.0929 footcandle (英尺烛光)
1 footcandle= 1 lm per square foot = 10.764 Lux
1 foot Lambert = 3.426 candelas per square meter ( nits)
1 nits ( candelas per square meter) = 0.2919 foot Lambert
5.了解了上面基本知识后，下面将亮度Candelas 转换成流明(Lm) - Converting Candelas to Lumens
流明＝光效×灯功率
Step 1.) Obtain the solid angle of the LED
w = p (q )2
w = p (25)2 , assuming the LED half angle is 25º
w = p (.43633)2, convert degrees to radians
w = .598
Step 2.) Calculate Lumens
f = Iv * w
f = 2.00 * .598, assuming the LED brightness is
2000mcd
f = 1.196 Lumens"
