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UltravioletPhotography

Filtered Nichia 395nm UV LED vs. Filtered Nichia 365nm UV LED


Pylon

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Has anyone experimented with other UV LEDs that are not advertied to be peaked at 365nm, but instead a larger number, such as 385nm, 395nm, etc? If so, I am wondering what the difference would be if they were both filtered with a U-340 filter. Any examples/tests anyone can show?
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I've got a Nichia 385 nm UV-LED.

But have never used it with a U340 filter.

You get a lot of violet/blue from the 385.

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When filtered, I am thinking 385, 395, or even the 405nm UV LEDs could work just as well as 365nm. If they are less expensive than 365nm and get results potentially better than or equal to 365nm, why waste money on 365nm?

 

An $8 filtered UV LED peaked at 395nm produces results better than or equal to a 365nm Nichia UV LED in terms of fluorescent effects. I was using the U-340 filter which has less transmission around 395nm but some still gets through. I suppose the hard part would be to find a filter that has a very sharp cutoff at 400-405nm, but with maximum transmission at 395nm. I wonder if there is anything like that.

 

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http://i.ebayimg.com/images/g/kz4AAOSwpdpVX5J6/s-l1600.jpg

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Hi Pylon, I take it that you have these other LED's? How do they seem to compare as far as output power intensity, which is a big difference between the cheap 365nm LED torches and the MTE 365nm torch.
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I have an $8 395nm LED torch and a $225 365nm MTE-301 torch. The $8 is much lower output when filtered (however this could simply be because of the U340 filter that was placed over the 395nm, look at the transmission level.)

 

If I were to filter my 395nm LED with a filter that had maximum transmission at 395nm but a sharp cut off at 400-405nm, we may find that the $8 LED has similar brightness to the $225 LED.

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I'll try to get an experiment done with my two Nichia flashes - 365 & 385 - with a couple of different filters.

 

One problem you might encounter is that certain subjects will not fluoresce as strongly with torches nearer the 400nm area. It depends on the subject and what wavelength it "needs" to fluoresce. OTOH, it most likely could work the other way around also. So, as always, experimentation is the order of the day.

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As Andrea noted, different materials have different excitation wavelength requirements depending on the root cause of their fluorescence.

 

Although 365nm seems to be what people generally think of when using LWUV to excite materials, the only reason for this is that it is a major UV emission line and was relatively easy to produce from the earlier days, so in some ways it became the "standard" LWUV wavelength. By coincidence, many materials do fluoresce to this wavelength but its not necessarily their strongest fluorescence response.

 

Be wary of many of the cheaper UV LEDs as their maximum emission can often be off from the stated "specification".

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