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UltravioletPhotography

[SAFETY WARNING] The green banana test


Stefano

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This Clive is handling al his many UV tests dangerously !

This banana one is also handled dangerously & the test is flawed in that he has placed the UV lamp in physical contact with the bananas & the heat of the lamp is also having an effect on the bananas skin.

He has done nothing to show that it is the UVC has cause the blemish.

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Andy Perrin
The burnt banana on the right was just in contact with ordinary blue LEDs, not UVC. The banana on the left was the UVC-irradiated banana (allegedly).
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The burnt banana on the right was just in contact with ordinary blue LEDs, not UVC. The banana on the left was the UVC-irradiated banana (allegedly).

Was the blemish caused by UVC or heat ?

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Andy Perrin

Was the blemish caused by UVC or heat ?

The burnt spots (blemish?) was caused by heat, which is exactly what he says in the video. Heat from the blue LEDs. The green stripe was caused by the UVC on the other banana. You should listen with the audio on!

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You should listen with the audio on!

You can hold the insults please. I am quite deaf thanks, but I was listening carefully. It is what I saw that I am commenting on.

The UVC lamp was resting on the banana, was it the UVC or heat that caused the bleamish ?

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Oh, sorry if I caused this.

 

I don't know how hot UVC bulbs get, we should ask David (dabateman), since he has experience in using them. They are around 30% efficient, so they do heat up. If you watch carefully, you can see a slight discoloration outside the area he delimited with the tape, where there wasn't tape (outside the square, hope I explained well).

 

The effect is caused by UVC light. In fact, the other two "UVC" lamps (actually UVA and blue) did nothing to the banana skin, apart from the burn spots on the banana on the right, which were caused by heat. That's how I understood it.

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Andy Perrin

Stefano is correct, and I was making a suggestion not an insult. Two of those three lights were not UVC. The one that got hot enough to burn the banana did not make a color change. I think the conclusion that the light wavelength was responsible for the color change seems reasonable to infer.

 

(Let me add that I did actually watch the video with the sound off first, then I rewatched it with the sound on to get the specifics. I figured you did the first and not the second watch, so that's what prompted the suggestion. Re-reading it, I can see why you took it as an insult, though.)

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I have at least 4 of those real UVC lights.

They don't get very hot. You can, but shouldn't, leave one on for 30 minutes to 60 minutes for imaging and then unscrew it from a desk lamp with your hand.

 

I was curious about those Led lights. I have seen them on Amazon for $50 to $100. Listed as 250nm LED.

I know 250nm LED exist, but are about only 1 to 2% efficient and horribly expensive.

 

Good to see I don't have to waste $50. I would love a led UVC light. The mercury ones can break easily.

 

I would still like to know what wavelengths they are. The 385nm LED bulbs I recently purchased wete only 400nm Leds. And equal 400nm output to my 405nm led bulbs.

 

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Regarding the wavelengths, eyeballing them, they should be 395 nm-ish for the middle lamp and maybe 460-480 nm for the blue one on the right. I think that the blue lamp imitates the blue-cyan glow of a true mercury bulb, which is given by the 435.8 nm blue-violet G-line and the 546.1 green line.

 

I don't know (maybe nobody does) if the germicidal lamp he used was the ozone-free 253.7 nm only type or if it was the un-doped version which passes the 184.45 line, so maybe the responsible for the color change was the 184.45 line.

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The ozone ones are rare and break too easy.

I would be very surprised if it was an ozone bulb. Most likely the common ozone free ones which have extremely broad spectrum.

I should post a screen shot, they have most mercury lines.

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To make things even clearer, in the video description there is a link to another video that inspired Clive. In that video you can see very well that heat is not the responsible for the color change.

 

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To make things even clearer, in the video description there is a link to another video that inspired Clive. In that video you can see very well that heat is not the responsible for the color change.

 

 

Thanks Stefano

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  • 1 year later...

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