Super-LumiNova material

Exactly, and several things can affect how bright the lume is. First the colour the lume is tinted can have a big impact on how bright it is:



Second, the amount of lume applied, so thickness and area. Then the grain size of the lume particles, and even if the background of the marker is painted (and what colour) can all affect the brightness of the lume. This in part determines how long it is effectively useful...

And to get a really good idea of how long it lasts, you need to have your eyes accustomed to darkness, and in a room that is quite dark to begin with. The cone cells in your eye adapt to darkness in just a few minutes, but the rod cells can take at least an hour to get fairly sensitive, and up to several hours before they reach their full potential for seeing in darkness. Any exposure to light can set this all back...

So shining a light on your dial and staring at it in essentially daylight conditions is not really a useful gauge of how long it really lasts in the dark.

Cheers, Al