What Color Luminant Is The Brightest And What Is The Best Lume?

Fred H. from Salt Lake City Utah, USA asks:

Thanks guys for the work on your blog, keep the pictures & reviews coming. My question today is: other than color is there a difference between green & blue lume? Also what advantages do Superluminova & tritium gas tubes have over regular lume? Finally, is there a minimum amount of light needed for lume to be really useful? For that matter is there a maximum amount of light exposure beyond which the lume will not work any better in the dark?

This is a larger subject matter and you ask a lot of great questions. Lume is a very important element on many watch dials that allows for night viewing. Traditional luminant is charged by light and then outputs a glow at night that decreases over time until the luminant is charged again. The most popular type of lume is SuperLumiNova, from the company "LumiNova." SuperLumiNova is very popular among high-end brands but there are some alternatives. Seiko uses its own lume, sometimes called "Lumibrite," for example.

Luminant must be charged by light, and the amount of time required to charge depends upon the brightness of the light. Sunlight is the best and just a few minutes will really charge up lume well. Indoor lighting doesn't fare as well. The more UVs the better. Below we have more information on the brightest luminant colors.

Tritium is a totally different type of lume that involves small, self-glowing tubes produced by Swiss MB Microtec H3. These tubes contain small, safe amounts of radioactive material and they come in various colors. While not as potentially bright as SuperLumiNova, tritium tubes don't need to be charged with light and will glow all night long. Tritium tubes tend to work for about 25 years until they need to be replaced.

Luminosity is measured in units called "lux." The standard for measuring lume is ISO 17514. The absolute minimum visible light is 1e-5 lux. You need instrument-grade hardware to measure that. Here's a plot showing 3 lume watches versus a tritium watch. Note that the tritium is constant at about 0.0004, and the lume is initially much brighter, crossing over around 200 to 5000 seconds later.

What Color Luminant Is The Brightest And What Is The Best Lume? Ask Us Anything

What Color Luminant Is The Brightest And What Is The Best Lume? Ask Us Anything

You can get more information on lume from aBlogtoWatch contributor Paul Hubbard's page.

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  • doxashark

    This is why I stopped buying Orient.  The lume sucks.  There’s no point in having a watch that you can’t read!  That’s why I’m a big fan of Seiko & Doxa; they’re all about the lume, baby!

  • Biffo10

    Not quite the whole story regarding the use of tritium.  Yes, tritium gas is used in gas tube
    technology ( GTT ) & has to be energised by electric current to glow. Tritium is a naturally
    found isotope of hydrogen & was historically applied to watch dials for luminescence. Due
    to a shortage worldwide in radioactive tritium & a more health & safety conscious world nowadays, tritium is not applied to dials. Divers rue the loss of tritium dials. Most of the brand names of luminous
    materials mentioned in this article need light to activate them, & there is little or no light at the
    murky depths of the oceans. Tritium fluoresced at a constant rate without the need for light. I
    don’t know what professional divers use now, maybe GTT watches. My Omega SMP lumes in the daytime with it’s Superluminova, but wouldn’t be visible at depth in the sea.

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  • steward1507

    Biffo10 I learned some years back the a black light (UV) works best for charging the standard lume on most watches. 4 or 5 seconds will last for quite a long time and gives a very bright glow.

  • Biffo10

    steward1507 Biffo10
    Now that’s an interesting observation !
    I started thinking about SOCO’s ( Scene Of Crime Officer )
    who bathe a murder scene with U/V light to reveal the presence
    of blood & study blood splatter patterns not visible to the naked
    eye in normal light.  I’m not saying blood lumes as such lol ! but
    it could just be that it, & Superluminova, can react atomically 
    & aggressively to the wavelength of U/V light , not just the 
    intensity of normal light ?

  • steward1507

    Biffo10 steward1507 They don’t use just a UV light they also use Luminol, they almost never show them spraying it at the crime scene tho. Luminol reacts to almost any organic chemical in the presence of UV. I used it routinely when I was in grad school 39 years ago (dating myself here a bit!). It is also used routinely in thin layer chromatography and paper chromatography to indicate where the separated compounds are to be found in relation to the reaction front, i.e.. the total distance the solvent has traveled.

    Heres 1 link, a google search will give many more;