Possible better UV filter stack?

[Cadmium]

Cadmium,

You may have a dead convoy on your hands. I have one like that. The other is good. But one transmit IR like that. I use it for the UV hot spot as its also weaker than the good one.

 

No, it is not a dead or defective one at all. They all work that same way with no U-340 filter.

There are many such examples on here of people testing filters and lenses with LED's and getting strange results.

This result is because the intensity of the Nichia 365nm UV LED, just like the intensity of many other modern LED's, they will go through even OD5, so what you are seeing (in my estimation)

with the Nichia example is 365nm penetrating through the OD of the lower 850nm longpass range. It only has so much OD, but not enough to block the intensity of the LED.

That is why I say, don't use LED's for direct tests, if you use an LED, us it for illumination of a target, don't shoot directly at the LED, that will not be a good or real test.

On the other hand a bandpass test filter of the sky is a much more real and natural test of a lens transmission.