Ever dove with a UV light?

[pisauron]

The yellow filter blocks UV, allows to pass visible wavelengths.

If you put it on *mask* (or camera lens), it will block whatever UV is being reflected and you will see better the light coming from object's fluorescence. Of course, placing it on torch only reduces its efficiency as it will block UV.

If you have a torch that is not pure UV, you may need the opposite filter on the light source: something that will allow only UV to pass

I'm confused. I have a dedicated uv scuba flashlight. He emits nm395 light.
Now i add a yellow filter to my mask. What will i see?

 

[Jai Bar]

I'm confused. I have a dedicated uv scuba flashlight. He emits nm395 light.
Now i add a yellow filter to my mask. What will i see?

You want to see the fluorescence caused by ultraviolet light, not the UV light itself.

The UV light from torch illuminates the corals, some species then emit light in *other* wavelengths and this is what you want to see. You block with filter in the mask (or lens) the stray/reflected UV up to blue wavelengths and thus enhance your perception of the light from luminosity of corals. We don't see UV but most lights (or at least the cheap ones) are not narrow 395nm and have some wider spectrum purple tint that you can filter out and get better contrast. Maybe also protection if you shine the light directly in your eyes- at night if only source of light is the UV torch also your pupils will be wide open.

I don't use any filters with my cheap UV light. For me it's part of the experience and as a side effect I hum Jimmy Hendrix's Purple Haze and my air consumption is increased

Many years ago I had an HID light that also emitted a little bit in the UV range. In that case the regular visible light was too strong and the UV/fluorescence effect was outshined. I improvised a UV pass filter on the torch itself that blocked most of the visible light except the UV wavelength, so now all I could see was almost nothing, just a barely observable faint purple. Until it hit corals and brought an asotnishing fluorescence. Now my cheap UV light is mostly purple but works so no complains.

In general photography, for example, uv filters are applied to remove haze etc.

 

[pisauron]

You want to see the fluorescence caused by ultraviolet light, not the UV light itself.

The UV light from torch illuminates the corals, some species then emit light in *other* wavelengths and this is what you want to see. You block with filter in the mask (or lens) the stray/reflected UV up to blue wavelengths and thus enhance your perception of the light from luminosity of corals. We don't see UV but most lights (or at least the cheap ones) are not narrow 395nm and have some wider spectrum purple tint that you can filter out and get better contrast. Maybe also protection if you shine the light directly in your eyes- at night if only source of light is the UV torch also your pupils will be wide open.

I don't use any filters with my cheap UV light. For me it's part of the experience and as a side effect I hum Jimmy Hendrix's Purple Haze and my air consumption is increased

Many years ago I had an HID light that also emitted a little bit in the UV range. In that case the regular visible light was too strong and the UV/fluorescence effect was outshined. I improvised a UV pass filter on the torch itself that blocked most of the visible light except the UV wavelength, so now all I could see was almost nothing, just a barely observable faint purple. Until it hit corals and brought an asotnishing fluorescence. Now my cheap UV light is mostly purple but works so no complains.

In general photography, for example, uv filters are applied to remove haze etc.

Thanks. So adding a yellow filter to myask will just make the corals a bit more bright?

 

[ScubaBunga]

Thanks. So adding a yellow filter to myask will just make the corals a bit more bright?

if you have a "blue" light - or weak UV (395nm range) the yellow filter should enhance the fluorescence. If you have a full UV (365nm range), I don't think the yellow filter is needed or does as much as it's used to filter out the blue light.

 

[Jai Bar]

Thanks. So adding a yellow filter to myask will just make the corals a bit more bright?

If illuminated by "blue" light/weak UV/395 source, then the filter on mask/camera lens will reduce some of the stray light that is visible (the "purple haze") hence the eye will perceive them better. They will not be actually brighter as the filter does not amplify the light or anything of the sort, it just reduces the stray light reflected from the torch.

 

[Jai Bar]

if you have a "blue" light - or weak UV (395nm range) the yellow filter should enhance the fluorescence. If you have a full UV (365nm range), I don't think the yellow filter is needed or does as much as it's used to filter out the blue light.

Correct. If there is no light in whatever wavelength then a filter for that wavelength is not necessary.

Not sure how many people know the actual spectrum of the lights they are using (I know I don't), and whatever most Chinese manufacturers claim is usually wrong (and most lights are made in China?).

Anyway, some say that blue/weak UV/395nm has actually better fluorescent effect on organisms, and most people I have seen diving with UV were using this type of light. Even without the filter it is really cool.
I have not compared the effect underwater as the only 365nm torch that I have is not compatible for diving.

 

[ScubaBunga]

Correct. If there is no light in whatever wavelength then a filter for that wavelength is not necessary.

Not sure how many people know the actual spectrum of the lights they are using (I know I don't), and whatever most Chinese manufacturers claim is usually wrong (and most lights are made in China?).

Anyway, some say that blue/weak UV/395nm has actually better fluorescent effect on organisms, and most people I have seen diving with UV were using this type of light. Even without the filter it is really cool.
I have not compared the effect underwater as the only 365nm torch that I have is not compatible for diving.

I got this one: UniqueFire D03 off Amazon and was happily surprised how bright it was underwater. It didn’t seem like it would be but had great range and was brighter than others on my trip. It says it’s 365nm and if it’s not, it’s at least closer than some other non-dive lights I have,

 

[dive.sendiri]

Some pictures I took with the uv lights. The lights I made myself using the existing uw torch body.