Chauvet - Colordash Par HEX 12 for UV Photography?

[The Skin Doc]

I recently spoke with someone that rents UV lights for his UV Photography. I found a light rental company that rents this light. It emits 10V of UV light, but doesn't mention the wavelength. Does anyone know if this will work for UV photography? Also, is it safe for my patients? Any help would be appreciated.

 

https://www.chauvetprofessional.com/products/colordash-par-h12ip/

https://www.chauvetprofessional.com/wp-content/uploads/2015/07/COLORdash_Par-Hex_12_UM_Rev2_WO1.pdf

[Guest]

The documentation for the light you found lists the UV component as "Purple", so I would guess this would not be very useful as a UV source. As for whether it is safe to use on people, I would recommend checking with a doctor first - because certainly UV causes damage, accordingly as a function of time/exposure, intensity, and skin type/condition.

[Andy Perrin]

Mark, this was a continuation of his other thread where there was discussion of light source safety.

[Andrea B.]

The UV Led is likely to be one of 365 nm or 380-385nm, both of which would reveal UV signatures.

 

If the Led is Purple, then it is probably 400 nm, which probably does not have a wide enough bandwidth to fully reveal UV signatures.

 

Any of 365, 380 or 400 nm lighting would require the usual safety procedures. Photographed patient must wear eye goggles or close their eyes.

 

I would suggest an email to Chauvet to ask what the UV Led peak wavelength is in their lighting. It seems strange that the UV wavelength is not mentioned anywhere in their lighting specifications.

 

But a $30 Convoy UV-Led flashlight (torch) would be a less expensive way to go.

[The Skin Doc]

The UV Led is likely to be one of 365 nm or 380-385nm, both of which would reveal UV signatures.

 

If the Led is Purple, then it is probably 400 nm, which probably does not have a wide enough bandwidth to fully reveal UV signatures.

 

Any of 365, 380 or 400 nm lighting would require the usual safety procedures. Photographed patient must wear eye goggles or close their eyes.

 

I would suggest an email to Chauvet to ask what the UV Led peak wavelength is in their lighting. It seems strange that the UV wavelength is not mentioned anywhere in their lighting specifications.

 

But a $30 Convoy UV-Led flashlight (torch) would be a less expensive way to go.

 

I'll be calling Chauvet on Monday, so I will post their answer ok. Also, I have a Jaxman Mini 365 UV Flashlight that works amazing. As always, thanks for the input.

[The Skin Doc]

The documentation for the light you found lists the UV component as "Purple", so I would guess this would not be very useful as a UV source. As for whether it is safe to use on people, I would recommend checking with a doctor first - because certainly UV causes damage, accordingly as a function of time/exposure, intensity, and skin type/condition.

I'm calling Chauvet on Monday. I'll post their response, ok!

[dabateman]

 

 

But a $30 Convoy UV-Led flashlight (torch) would be a less expensive way to go.

 

No Don't do that!

 

His purpose is to light and image people's skin. He is currently using a Canon macro lens which just sees to 380nm.

 

Careful about your recommendation, as for flowers yes a 365nm Convoy flashlight would be best.

 

But for his needs just buy a $30 four pack of 385nm LED bulbs from Amazon. You will be surprised to how much more light you will see with your current gear and will be able to drop your ISO.

[Andy Perrin]

Yeah, a 365nm torch with a lens that cuts at 380nm is a bad idea. Also, the longer wavelengths are somewhat less dangerous (although that curve Jonathan linked in the other thread of the damage vs wavelength shows that it doesn’t change much in the longer UVA).

 

Everyone, the other thread is here:

https://www.ultravioletphotography.com/content/index.php/topic/3603-indoor-uv-portrait-using-uv-lamps/

[Andrea B.]

I don’t see anything about a Canon macro lens (380 nm reach)? But certainly agree that you wouldn’t use a peak 365 nm light source with a lens which doesn’t reach that far.

 

But I have a question here: is there a recommended peak wavelength for UV dermatological photography?

And, why not use, instead of narrowband LEDs, a broadband light source for such work? (With eye protection, of course.)

 

ADDED Later: Melanin peak absorption is below 350 nm, so wouldn’t it be better to shoot dermatology with gear which passes UV below 380 nm if you are looking for UV damage beyond surface textural changes? I’m just asking out of curiosity and to improve my own knowledge. There are undoubtedly many factors at play in assessing skin damage so my speculation here about shooting below 380 nm, might be all wrong. OTOH, experience with floral UV signatures has shown me that most of them show up about the same at 380 nm as at 350 nm. Only floral false color changes between, say 350 nm and 400 nm but floral absorption areas are mostly the same. So maybe that’s also true for skin signatures?? Well, I’m rambling....., but it is a very interesting question as to what is the “best” peak wavelength for dermatologic photography.

[JMC]

My ears were burning. Andrea, I've measured the transmission of the Canon 50mm f2.5 Macro lens - https://www.ultravioletphotography.com/content/index.php/topic/3406-lens-transmission-in-the-uv-latest-update/page__view__findpost__p__29227

 

There are I believe 2 versions of this lens. Mine was version 1. As for transmission, it's not great. However at 385nm it would still be over 50% max transmission. By 365nm, it's down at around 15% max transmission. So yes, 385nm would be better for this lens.

 

As for the best wavelength for looking for skin damage, it is complex, and depends on what skin damage you are looking at (and where that damage is in the skin). Different wavelengths penetrate to different depths within the skin (typically shorter wavelengths penetrate less deeply). The main chromophores in skin are melanin and haemoglobin. Both melanin and haemoglobin absorb strongly in the UV, but melanin is higher up in the skin than haemoglobin, and it's the melanin that tends to dominate a skin picture.This is why freckles look darker in UV images. This is good for looking at UV initiated skin damage as melanin increases after sunexposure. As for whether 365nm would be better for showing this damage than 385nm, I'm not sure.

 

There is also the safety aspect to consider. I've mentioned about the erythemal action spectra before, and the shorter wavelengths have a much higher risk is initiating burning of the skin. If it were shown that 300nm was the best light to image skin damage with, the safety aspects of that would preclude its general use.

 

The erythemal action spectra is on a logarithmic y axis scale, and the issues from UVA exposure are much less than those from UVB with regards to sunburn. While in order to calculate how long it would take before the risk of burning with a light light that I'd need to know the spectra and the distance from subject to light source, you could get an idea about exposure by comparing how long it takes to get a UV reflectance image compared to sunlight. If it takes 3 stops more exposure to get an image with this light vs normal sunlight then it's not that intense and the risk of skin damage would be low. If it takes 3 steps less exposure with the light vs sunlight then be wary of exposing the skin to it for more than a few seconds. This is a quick and dirty test, and does not take into account the spectral distribution in the light source, and of course is based on the filter used as well and the camera sensitivity. It has a number of other assumptions (such as, is the camera responsive to all the wavelengths the filter can let through) but sometimes, a little data is better than no data at all, as long as the limitations of the data are understood.

[Andy Perrin]

I wonder if it could be rigged up as some kind of speedlight, so that it would only be on as long as needed?

[dabateman]

My concern is always that a patient didn't have a problem. But after 1 minute exposure to 300nm, now complains about burning.

I would try to stay in the safer end of 380nm to 405nm.

I haven't looked into the research papers, but that would probably be the best source for this discussion.

I do know that Pmel17 forms an amyloid structure which helps melanin form. Not relavent to this discussion, but cool as a functional amyloid protein.

[ulf]

In the standard

IEC 62471

Photobiological safety of lamps and lamp systems.

 

there is a table for weighting the hazard as a function of the wavelength for UV-light sources.

It is used together with different exposure levels when evaluating light sources with varying spectral intensities like discharge-lamps and LEDs.

The table seams to be normalised against the intensity at 270nm

 

I have no idea about the grounds the table is based on, but as an international safety standard I assume that it is rather well prepared.

The standard document with the original table was published 2014.

 

It is interesting to compare the weighting numbers for wavelengths that often are interesting for us like 385nm, 365nm and a bit into UV-B.

 

---

[JMC]

There's an interesting document here, which covers a few of the different models for skin damage as a function of wavelength.

 

https://ec.europa.eu/health/scientific_committees/scheer/docs/sunbeds_co121c_en.pdf

 

As can be seen with all the models the risks from UVA are much lower than those from UVB. So LEDs which are 365nm or 385nm present a much lower risk than things like fluorescent tubes with UVB and UVA peaks.

[dabateman]

Jonathan thats an excellent reference. Especially appendix A and B. Its looking mostly a solar UV and notes that there was zero solar Uv measured below 280nm.

Whats interesting is the probability of cancer and DNA damage hits below 340nm and 330nm respectfully.

 

So lets all stand in front of our 302nm light sources and become the fantastic four. Sarcasm alert, don't do that. Just as Adam West rolled around in Nuclear waste in a family guy episode. You will just end up in a hospital.

 

This also seems to be a good source of information:

https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.icnirp.org/cms/upload/publications/ICNIRPUVWorkers.pdf&ved=2ahUKEwij-8vUjuDmAhVwuVkKHUFNAwIQFjAGegQIBhAB&usg=AOvVaw0hCZUB0PbLcnJHiu7GGUkH&cshid=1577803634537

 

[Andrea B.]

Interesting discussion.

 

Safety with UV illumination is always an issue, and I'm happy to see everyone paying good attention to the safety factor.

 

My basic curiosity is whether 365 nm and 385 nm human skin photos show many differences? It is easy enough to make a few photos in good strong sunshine under both filter wavelengths and see what shows up. However, as Jonathan has pointed out, it all depends on what you are looking for.

 

I am quite sure that I would NEVER recommend to anyone to make human skin photos under UV-LED illumination below a peak of 365 nm. And whenever UV-LED illumination or UV-flash is used, the subject MUST be wearing eye goggles.

 

Hey there, does it worry any of you all when you see crowds of people dancing around under black lights at parties or clubs or wherever? It sure does worry me!! I recall dancing around a few times under black lights in certain of my earlier years (about which the less said the better). I can only hope those were "purple blacklights" around 400 nm that I was dancing under. But who knows? :blink: :blink:

[Cadmium]

Interesting discussion.

Black lights have always been a question to me.

When I measure a Nichia 365nm LED with my Sparticle bandpass array, I see a very limited band of UV,

whereas when I measure a common black light bulb found in almost any store, I see a wide range of UV, spanning the entire array of bandpass filters from 325nm to 400+nm.

So even though we have all grown up to think nothing of black nights, I wonder how harmful they really could be, especially for our eyes, and especially when looking directly at them.

I know the LED's are much more intense than the common black light, but given the much wider and deeper spectrum of black lights (at least the one I have),

I wonder it looking at this in close proximity as photographers do, if those may be harmful to our eyes. I have never seen any warnings for such bulbs.

 

Have a happy New Years Eve, everyone.

[The Skin Doc]

My ears were burning. Andrea, I've measured the transmission of the Canon 50mm f2.5 Macro lens - https://www.ultravio...dpost__p__29227

 

There are I believe 2 versions of this lens. Mine was version 1. As for transmission, it's not great. However at 385nm it would still be over 50% max transmission. By 365nm, it's down at around 15% max transmission. So yes, 385nm would be better for this lens.

 

As for the best wavelength for looking for skin damage, it is complex, and depends on what skin damage you are looking at (and where that damage is in the skin). Different wavelengths penetrate to different depths within the skin (typically shorter wavelengths penetrate less deeply). The main chromophores in skin are melanin and haemoglobin. Both melanin and haemoglobin absorb strongly in the UV, but melanin is higher up in the skin than haemoglobin, and it's the melanin that tends to dominate a skin picture.This is why freckles look darker in UV images. This is good for looking at UV initiated skin damage as melanin increases after sunexposure. As for whether 365nm would be better for showing this damage than 385nm, I'm not sure.

 

There is also the safety aspect to consider. I've mentioned about the erythemal action spectra before, and the shorter wavelengths have a much higher risk is initiating burning of the skin. If it were shown that 300nm was the best light to image skin damage with, the safety aspects of that would preclude its general use.

 

The erythemal action spectra is on a logarithmic y axis scale, and the issues from UVA exposure are much less than those from UVB with regards to sunburn. While in order to calculate how long it would take before the risk of burning with a light light that I'd need to know the spectra and the distance from subject to light source, you could get an idea about exposure by comparing how long it takes to get a UV reflectance image compared to sunlight. If it takes 3 stops more exposure to get an image with this light vs normal sunlight then it's not that intense and the risk of skin damage would be low. If it takes 3 steps less exposure with the light vs sunlight then be wary of exposing the skin to it for more than a few seconds. This is a quick and dirty test, and does not take into account the spectral distribution in the light source, and of course is based on the filter used as well and the camera sensitivity. It has a number of other assumptions (such as, is the camera responsive to all the wavelengths the filter can let through) but sometimes, a little data is better than no data at all, as long as the limitations of the data are understood.

 

I have to apologize for saying I used a "Canon 50mm Macro" lens for the above photo. I was reminded by my nurse that I used a "Canon Macro 100mm 1:2.8". I never intended to use this lens for UV photography, but it was the only lens I had with me that day. I'd be interested to know your opinion on this lens.

[JMC]

I have to apologize for saying I used a "Canon 50mm Macro" lens for the above photo. I was reminded by my nurse that I used a "Canon Macro 100mm 1:2.8". I never intended to use this lens for UV photography, but it was the only lens I had with me that day. I'd be interested to know your opinion on this lens.

I've not tested that lens yet, but I doubt it transmits much UV (or goes very far into the UV). Lovely lens, but a lot of lens elements and coatings. If I get chance I'll do a transmission measurement as I have one somewhere. Based on this, you'd be better off with a 385nm light source if possible for both the 100mm and 50mm Canon macros.

[The Skin Doc]

I've not tested that lens yet, but I doubt it transmits much UV (or goes very far into the UV). Lovely lens, but a lot of lens elements and coatings. If I get chance I'll do a transmission measurement as I have one somewhere. Based on this, you'd be better off with a 385nm light source if possible for both the 100mm and 50mm Canon macros.

Thanks, your responses are always valued! Quick question, what is the best UV wavelength to view sun damage in skin? I'd like to compare it to your UV safety chart. Thanks in advance!

[JMC]

That's a very good question, and not one I know the answer to (see my response to Andrea above). If you're looking at Melanin as a marker of sun damage then, as the wavelength gets shorter, the more the melanin absorbs and stands out, but the risk of burning goes up. For imaging purposes I think the best trade off is the 360-390nm region, combined with a good uv filter (with decent visible and IR blocking). If you're using those lens you mentioned, go with 380 to 385nm as at 365nm you wont get much UV through them.

[The Skin Doc]

That's a very good question, and not one I know the answer to (see my response to Andrea above). If you're looking at Melanin as a marker of sun damage then, as the wavelength gets shorter, the more the melanin absorbs and stands out, but the risk of burning goes up. For imaging purposes I think the best trade off is the 360-390nm region, combined with a good uv filter (with decent visible and IR blocking). If you're using those lens you mentioned, go with 380 to 385nm as at 365nm you wont get much UV through them.

 

Thanks once again. Also, I did use a Jaxman mini 365nm UV flashlight to prevent shadows on the forehead since the UV lamps were lower on the ground.