Do you know about luminance and duration characteristics of glow in dark powder

About the brightness of luminous powder in the new customers often have doubts, clearly said that the manufacturer can be bright for 10 hours how to see half an hour, causing some unnecessary misunderstanding.
The luminance of luminescent materials is usually measured in units of CD /m2(candela per square meter), while noctilucent powders are usually measured in units of MCD /m2(Millicandela per square meter).
The midday sun reaches 10,000 to 100,000 CDS /m2,
In the daytime, there are only 1000 ~ 5000cd/m2 in the room.
And our light at night is usually between 100 and 1,000 CD /m2,
The brightness of emergency lights should be greater than 50CD /m2,
New electroluminescent signage, brightness only 20 ~ 100cd/m2,
The maximum brightness of luminous powder products will not exceed 10CD /m2, and it is at the moment when the excitation light source stops, the brightness is only 1 ~ 2CD /m2 after 2 minutes, 0.060 ~ 0.0990 CD /m2 after 1 hour, and 0.006 ~ 0.010 CD /m2 after 10 hours.
Therefore, when observing the luminance of noctilucent powder in the daytime, due to the existence of ambient light (even in a dark room, it will exceed 1cd/m2), but our eyes feel very dark due to the strong contrast between outdoor and indoor. In such an environment, the luminance of noctilucent powder is usually not observed within an hour or so. If with a drawer or paper tube what to avoid light observation, so more than 10 minutes to see the luminous powder.
Why then we noctilucent powder manufacturers said may shine about 10 hours, the reason is that people can be observed under the condition of eyes in the darkness of the light is very weak 0.00032 CD/m2, and usually noctilucent powder brightness attenuation to the brightness of the following time can reach more than 10000 minutes, that is to say, can continue to shine for 10000 minutes (166.67 hours) theory, the eyes can see. In order to illustrate the luminance of noctilucent powder, in the early promotion of long afterglow noctilucent powder, said to be able to shine for 8 hours and 10 hours, and usually only lasts less than 1 hour of zinc sulfide noctilucent powder to distinguish. In order to accurately express and testing instruments, to popularize and apply now gradually replaced by the data for 1 hour, due to large unit of CD/m2, so luminous powder usually adopts the MCD/m2 (candela per square meter), usually an hour brightness are between 10 ~ 100 MCD/m2, different level of granularity and the product brightness is different, because the brightness is higher, the greater the noctilucent powder particle size and large granularity using performance is bad, so under the condition of the same brightness, the smaller the particle size of product, the more high-grade, of course the price is more expensive, in order to save the cost of materials, Generally will be in the process conditions allow the choice of coarse products to achieve higher product brightness.