I want my MTE

[Cadmium]

Do you remember that line? "I want my MTV..." (Dire Straits, I think).

"Why does my MTE still show white light on my hand and other objects, even when there is a U-340 2mm filter installed to block visual light leaking above 400nm?"

I am asked that question a lot.

Some would think this light is visual leaking through the U-340 2mm filter, but no it is not.

The Hoya U-340 2mm filter blocks the MTE visual range leak.

Schott GG400, GG420, GG435... and/or Wratten 2E will block UV light.

Stacking U-340 2mm with GG400 or Wratten 2E will show no transmission.

So here is my demonstration showing that there is no visual leak transmitting through the U-340 2mm on the MTE.

 

WARNING: Be very careful with MTE torches and other UV light sources, especially when they are filtered with U-glass, such as U-340 2mm, don't look at them, or point them at people, or animals.

Your eyes can't see any light coming out of a filtered MTE torch, you can damage your eyes (or others people eyes) if you (or they) look at the torch.

You can't tell if the MTE is turned on or off when it is filtered, you will need to point the torch at something to see if it is turned on.

Wear UV eye protection.

 

[Cadmium]

This was an afterthought, but here is a test showing some visual leak difference between using the MTE with and without the U-340 2mm filter installed.

 

Using GG400 instead of Wratten 2E for this test shows the same amount of visual leak on the target, but with some added glass fluorescence.