As far as I know, Tritium is no longer used as luminous material in watches because it's radioactive. There is one exception to the rule, and that's the Traser technology. This company puts a Tritium containing gas in tubes, and uses that as the luminous parts on a watch.
There is a fundamental difference in the way (Super)Luminova and Tritium give off light.
Tritium is radioactive, and gives off energy in the form of light completely independent of external light sources. That means that it will still work after days or even years in the dark.
Luminova on the other hand is dependant upon outside light sources. It's able to "capture" this light, and give it off again once in the dark. The brightness depends on the time, intensity and colour of the light that it was exposed to before. Also the intensity of the light emission will decrease pretty fast.
What this all means is that Luminova is very impressive when entering the dark with a watch that was just exposed to a bright light source. It will literally outshine Tritium. Pretty soon however the intensity will become a lot less, and after a fairly short while, it will be less then Tritium, and before the night is over, Luminova will be hardly readable while Tritium will be just as bright as it was when the night started.
Here are a few pictures I made sometime ago to show you what I mean.
Side by side are my 4 Star Maritime, using a lot of Luminova on a black dial, and my H3 P6500 with Traser, also on a black dial. I lighted them for about 10 sec with a 300 watt halogen light source, then darkened the room and made 4 pictures. The first immediately, the second after about 5 min, the third after 15, and the last one after 30 min. Judge for yourself. The pictures are not very sharp, but you'll get the point.
And this is only after 30 min! After several hours the Luminova will have lost most of it's luminosity, but the Traser will still be just as bright. It has to be said though, that Tritium will loose its radioactivity slowly over the years.
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