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UV and Your Eyes :: UV Safety Reference

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#21 Andrea B.

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Posted 20 November 2015 - 18:02

...and that link has some good warning fotos !!

I now wear facial sunscreen every day. Only wish I had done that in my 20s, but we were not so aware back then (a thousand years ago).
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#22 Pylon

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Posted 22 November 2015 - 07:38

EDITOR's NOTE: Please read our post UV and Your Eyes :: UV Safety Reference.
You must always wear protective UV-blocking goggles when using artificial UV illumination.
UltravioletPhotography.com does NOT support UV-flash used on human eyes.
**************************************************************


Posted Image

I was wearing contact lenses in the above UVIVF picture that said they were "uv-blocking". If you look at my picture I posted, you can see how my eye lens is illuminated/fluorescing in the center... you do not get that with visible light. Therefore, a significant amount of UV light must be passing through these contact lenses, how much I don't know, as there is no measurement listed and I haven't measured anything myself, but it intuitively looks like a very significant amount to me and I don't plan on taking any more pictures like that using these lenses. There is no mention of the FDA on the packaging despite the box saying it is "uv-blocking" several times. I emailed the company asking what percentage it blocks and haven't heard back yet. It doesn't look like much when looking at the picture though.

Quote

Not all contact lenses cover the entire pupil of the eye.
Not all contact lenses have UV blocking capability.
In contact lenses which do have some UV blocking, the amount varies.

I was assuming that the contact lenses would cover the entire pupil+iris (I didn't know smaller contact lenses existed?) and would block UV to a significant degree.

Quote

Additionally, UV light doesn't just harm the pupil/cornea/lens of the eye, UV can also harm the white area of the eye (called the conjunctiva) by causing pterygium, which are raised, pinkish lesions. The condition is sometimes called "Surfer's Eye". Pterygium can grow and eventually interfere with vision by pulling on the cornea or by covering part of the pupil. And big pterygium are really gross looking!!
UV can also cause other types of lesions on the eyelids or eye rim.

If this is true, then I no longer see iris-large UV-blocking contact lenses as a valid solution to my goal (my goal being flashing an eye ~1-50 times) if the susceptibility-to-damage level is significant for the white part of the eye ("significant" meaning, it wouldn't just briefly irritate the eye for a little while and then eventually go back to being healthy after a day, but it would probably permanently damage it beyond natural repair, cause it to develop something bad that is difficult or time-consuming to remedy, or significantly increase the eyeball's chances of developing a cancer or some other bad thing over its lifetime, or significantly add to the cumulative damage). I am going to go off the assumption that all of that bad stuff could potentially happen if the white part of the eye was flashed ~20+ times (but I am not even going to do it once, myself).

If Class I UV-blocking iris-large contacts are not an adequate form of protection, then I now wonder if Scleral or sclera contacts would be an adequate form of eye protection (these cover even the white part of the eye), assuming you could find some that blocked 90%+ of UV-A. While these do cover a much larger area of the eye, it may not cover absolutely every crevasse around the edges that may require protection to lower the level of risk/damage to a low amount... Then again though, perhaps it would be a very good form of protection and be adequate. Then again, this picture is not a pleasant thing to imagine happening to someone at all and makes me resistant to the idea of using anything but goggles, although I am going to take a guess that is a severe case caused by the right conditions, such as a surfer with no eye protection getting blasted all day, day after day, with salt water and UV radiation getting reflected off the water, and who may already be vulnerable to getting pterygium by some genetic disposition. In any case, it may not be worth the risk to use full-eye uv blocking contact lenses, although if for whatever reason someone did, they would want to apply some sort of sunscreen to the eye lid and eye rim, the rim being the most difficult part, because you probably would not want to get sunscreen in your eye. If for whatever reason they DID develop pterygium, they would probably want to attempt to remedy it ASAP.

Also, if contact lenses did block 90%+ of UV-A, the lens would basically just turn black if you were to take a pure UVIVF photograph of them, which may or may not be an effect one would want in a photo.

One thing I was thinking about doing was using UV-glowing contact lenses in my photography, however by the sounds of it, it doesn't seem like that would be a good idea anymore, even if I were to flash them only 1-10 times. None of the fluorescent contacts I see being sold online say they are UV-blocking, and even if they were uv-blocking, if you are saying the white part of the eye could get significantly damaged beyond natural repair, or get a significant amount of cumulative damage added that is worth worrying about, then that idea (for me anyway) is no longer worth considering.

My goal was to UVIVF-photograph models with their eyes and skin visibly shown (ie. no glasses or clothing), so I was trying to understand what the "limits" were with UV-A radiation exposure and perhaps find solutions for overcoming them (ie. contact lenses and sunscreen) before pre-maturely/cynically abandoning the goal altogether. It is easy to assume the principal "never ever expose any amount of UV-A radiation to any living organism, as that is the safest thing. Only photograph inanimate material while being completely covered and with eye protection.", but I want to photograph people and other living creatures, so I am wondering what levels of UV a human eye or human skin can tolerate before becoming permanently damaged beyond natural repair, although maybe there are too many unknown factors that make predicting the "risk/damage level" impossible, and cumulative damage is unavoidable but something you would want to be aware of how much more you are adding to an organism nonetheless.

My original thinking (and I still do think this), is that if you go out in the sun for 5 minutes, that is not going to kill you or be extremely harmful to your skin in anyway, for the average person who is semi-adapted to being in the sun for extended periods. It probably won't take a year or more off of your estimated lifespan, it may age your skin a little bit and add that much more to the cumulative damage, but probably not enough to stress out over the event or stop you from going outside for that 5 minutes to do what you want/need to do in that moment (in fact, I would argue that stressing out over it would probably reduce your lifespan moreso than just going outside for 5 minutes). Therefore, if you get exposed to UV radiation from say 5 flashes, and the amount of radiation exposure from that adds up to roughly the same amount you would get from being out in direct sunlight for 5 minutes, then that is a very useful thing to know and be aware of - it gives you some sort of idea about what you are doing and what you are getting yourself into and could also potentially help when making an off-hand judgement about photographing other organisms. Otherwise, we are back at the principal that exposing any biological material to any amount of UV-A (or even UV-B/C) is simply off limits... and that may very well end up being an unfortunate undeniable realization that could be made at the end of this to be honest! I am not talking about eye protection in this paragraph as much as I am skin protection.

As of right now though, as far as what I can tell, and correct me if you understand this line of thinking to have flaws in it for whatever reason, it sounds like if I were using two UV flashes (lets say the UV-filtered Canon 199A and the Vivitar 285HV) no closer than 1 meter away from a model, with the model having a thick layer of zinc oxide SPF 30 UV-A/UV-B sunscreen applied to their entire body (I believe I read somewhere that zinc oxide is the strongest kind, especially for UV-A) and was wearing uv safety glasses that blocked 99% of UV-A, and I took roughly 20-200 shots of them over 1-4 hours, with those shots having their eyes closed under the glasses most of the time anyway, that this would be considered "safe"? If so, would also getting a few shots (lets say no more than 5-25) of their eyes closed also be "safe", assuming they weren't wearing safety glasses for those shots, but had sunscreen applied everywhere around their eye, to their eyelids, their eye rim, and their entire body? "Safe", in my current conception of the word, is not permanently damaging a functional biological system beyond natural repair, and no more than 1 year taken off the organisms estimated lifespan, and not increasing someone's risk to developing a cancer within their estimated lifespan by more than 2%. Maybe there is a better definition although this is what I came up with, I am not sure how to incorporate the idea of cumulative damage into a "definition" of "safe", other than the more decisions you make to avoid radiation on a day-to-day basis during your life as a whole, the more slack you might have when making the decision to get exposed to it every now and then.

I don't know how much UV radiation is getting pumped out of a Canon 199A flash, although I do know according to a UVIVF picture test I did that the 199A appeared at least twice as bright as the MTE-301 @1/160sec. when measured and compared only in the center of the LED beam (see picture below), even though the flash has a MUCH wider AND evenly lit area of coverage than the MTE301 (I am going to take a guess that the 199A overpowers the uv levels of the sun by at least 8x or more when the cumulative uv levels from both the sun and the flash are measured over a duration of 1/250th of a second). 100 flashes that last ~1/250th of a second each will only add up to a total of a few seconds of UV radiation exposure, with plenty of resting time between each flash, which doesn't sound like much exposure time at all, however we are talking about a UV light source that is several times more powerful than the sun, so that makes me question it! I am going to guess that sun screen will take away any doubt - the only doubt left in my mind I am now thinking about is sufficiently protecting the eye rim of the model, if you are thinking that could be an issue.

F4 / 1/160 / ISO 3200. Left is MTE301, Right is 199A. Both were at same distance away from door (~1 meter).
Attached Image: compar.JPG



Quote

UV can also cause other types of lesions on the eyelids or eye rim.

I don't like hearing this, especially about the eye rim, because it is difficult to apply sunscreen to the eye rim. It is easy to apply sunscreen to the eye lid though. Perhaps I'll try to limit the amount of shots I take with their eyes closed when they're not using sunglasses, if I can't get some form of sunblock applied to their eye rim.

I would intuitively think taking 1-5 shots of a person with their eyes closed with no sunscreen or UV safety glasses on would be okay, but any more than that is pushing it into the "I'd really rather not continue doing this anymore than we have to, and I'd appreciate it if you would stop now, please." narrative.

-

And now a new list of questions:


Question 1: I completely understand that using eye protection when exposed to UV radiation for whatever reason is very important. When using these flashes though, I wonder if it is important to protect your skin as well, or if that isn't as important. I would think if photographing a model several times in a session where they would get exposed to probably 10-200 flashes, that it would be very important to have sunscreen on them and on myself as well, however as a photographer going around and using these flashes all the time on a weekly basis, some of the UV light is getting reflected back and hitting your skin, be it photographing a flower in your house or going around outside with the flash attached to your camera. When I go outside, I have just been wearing my prescription eyeglasses (which block some UV light) in addition to closing my eye lids when firing the flash, and I was thinking that is good enough, although what you said about the eyelids and eye rim makes me second guess myself and makes me think that closing my eyes is not good enough and that goggles should now be used. I am wondering if others here think the same. And then even after doing that, what about your skin on your face, let alone the skin on your eye lids? The only way to get some sort of answer would be to know how much uv radiation the flash pumps out, and even then it is impossible/impractical to factor in all the different variations of angles and ambient reflections over the dozens of shots being taken in any session to come up with a realistic exposure limit recommendation. I suppose its ultimately a subjective thing that is up to the individual about how much protection they want to have. The more the better, but more can also be inconvenient (meaning I'd rather not have to wear gloves, face masks and sweatshirts if it is warm everytime I go outside to take a batch of 50-100 UV-A photos of plants every other week or so). So far I have not gotten any sunburn from doing that but that doesn't at all mean I could be paying for it later in life, although I've have had my sweatshirt on every time so any potential damage I've gotten so far over the ~1000 images I've shot is probably low, with most of it being on my face (and eye lids!). Here is an article that talks about how your eyeball is not the only thing that is vulnerable, but also all the skin around and near the eye: http://www.skincance...-to-skin-cancer

Question 2: Does the Canon 199A flash tube allow any UV-B radiation to pass through it? (I am assuming no UV-C would pass, even if there was any, correct?). What about the Vivitar 285HV?

Question 3: Are there any foods/drugs/substances/chemicals that can be taken orally, or applied to your skin (besides sunscreen) or eye, that could increase your immunity/resistance towards UV-A skin or eye damage? Are there any known genetic modifications that could be applied to a human at any age that could increase their immunity toward UV-A skin or eye damage?

An answer to 3: Astaxanthin can be taken orally to reduce UV damage. "....astaxanthin appears to provide some degree of sun protection through multiple mechanisms. First, it blocks a modest amount of ultraviolet light directly (not enough to be an effective sunscreen by itself but still useful). Second, it neutralizes some of the free radicals induced by UV radiation and responsible for some of the sun damage. Third, astaxanthin appears to inhibit the induction of matrix metalloproteinases (MMP) by UV light. (MMP are an important factor in sun damage and skin aging.)" - http://www.smartskin...staxanthin.html

Question 4:How would one go about measuring the amount of UV-A radiation from a flash, so that that number can be compared to the numbers of the Blak-Ray, MTE-301, and the sun? I am assuming you would need some sort of machine to do that. Just wondering what it would be called.

Question 5: If you were to take photos of a person wearing material that fluoresces brightly, such as white cotton or UV-reactive contact lenses, would that be any more damaging to the person wearing those things (or even you as the photographer who receives the bounced-back light) than if they were wearing material that does not fluoresce as bright?


I get that this is a very long post and that responding to every little thing might be exhausting, I by no means expect a response to all questions but would be grateful if anyone knows the answers and can respond to any of them

Edited by Pylon, 26 November 2015 - 05:37.


#23 Alaun

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Posted 22 November 2015 - 15:12

Perhaps one further question: Why do you think all modern flash now come with UV-protection?

(Just relying on the sun, I think it is possible to do model shooting outside in summer without flash,
both pics with Pana GH3 mod for uvir, uv-nikon and Baader U, no flash, the second one was a "grab" shot, so not that precisely focused ;-) )

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Edited by Alaun, 22 November 2015 - 15:16.

Werner

#24 Alaun

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Posted 22 November 2015 - 15:36

Maybe this a bit of help:





DIRECTIVE 2006/25/EC OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL
of 5 April 2006
on the minimum health and safety requirements regarding the exposure of workers to risks arising from physical agents (artificial optical radiation) (19th individual Directive within the meaning of Article 16(1) of Directive 89/391/EEC)

It also covers the exposure due to lasers and how to calculate the exposure (laser can have a similar type of light as flashes with respect to high energy in a very short time and multiple times, so I assume the calculation for flashes is similar)


Werner

#25 Andrea B.

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Posted 22 November 2015 - 16:18

Thanks, Alaun.
We have elsewhere posted some links to such health and safety directives.
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#26 Andrea B.

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Posted 22 November 2015 - 16:21

Pylon, I need you to simply give up your idea to UV-flash photograph any models or yourself. Most certainly you can be creative with UV photography and models in other ways that do not involve UV-flash.

I would remind you that you are opening yourself up to all kinds of lawsuits here in the litigious US if you UV-flash people, and they later decide that you have somehow screwed up their eyes and/or skin !!

As for your new questions, while they are very good, they require research into the medical literature to see if answers exist.

Our resident expert on biochemical issues is John Dowdy, so I suggest you contact him privately to see if he can be of any assistance. Although I think he will simply repeat what we have said before: no UV-flash in human or animal eyes.

***************************

I was assuming that the contact lenses would cover the entire pupil+iris (I didn't know smaller contact lenses existed?) and would block UV to a significant degree.
Contact lenses: Gas permeable contact lenses are tiny and do not cover the entire pupil.

My original thinking (and I still do think this), is that if you go out in the sun for 5 minutes, that is not going to kill you or be extremely harmful to your skin in anyway, for the average person who is semi-adapted to being in the sun for extended periods.
The UV damage is CUMULATIVE.

"Safe", in my current conception of the word, is not permanently damaging a functional biological system beyond natural repair, and no more than 1 year taken off the organisms estimated lifespan, and not increasing someone's risk to developing a cancer within their estimated lifespan by more than 2%. Maybe there is a better definition although this is what I came up with, I am not sure how to incorperate the idea of cumulative damage into a defintion of "safe", other than the more decisions you make to avoid radiation on a day-to-day basis during your life as a whole, the more slack you would have when making the decision to get exposed to it every now and then; it wouldn't be increaing your cumulative risk as much.
Unless you have actual medical data to support this concept of "safe", then it is just so much hogwash. What are you trying to do - play God with such silly statements as 'no more than 1 year taken off an organisms life span'? Who are you to even make such statements? And for many types of UV damage, there is NO natural repair.

I am not sure how to incorperate the idea of cumulative damage into a defintion of "safe".
Well, you don't.

measuring the amount of UV-A radiation from a flash
Look up the manufacturer's data. UV-flashes also put out UV-B.

If you were to take photos of a person wearing material that fluoresces brightly, such as white cotton or UV-reactive contact lenses, would that be any more damaging to the person wearing those things (or even you as the photographer who receives the bounced-back light) than if they were wearing material that does not fluoresce as bright?
Most UV-induced fluorescence is visible light - which is why you can see it. What you cannot see is any possible UV-reflection.
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#27 Pylon

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Posted 22 November 2015 - 20:43

Quote

Pylon, I need you to simply give up your idea to UV-flash photograph any models or yourself.

Giving up now would not make any sense. Surely there is a solution for protecting skin and eyes from UV-A radiation?

Edited by Pylon, 22 November 2015 - 20:49.


#28 Andrea B.

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Posted 22 November 2015 - 21:01

Presumably you have read the various recommendations across the site to wear UV-blocking goggles. And protective clothing. (Although I do not have much info on that at hand.)

I think we have adequately covered the protection thing.
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#29 Pylon

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Posted 22 November 2015 - 21:43

I know about safety glasses, and that thicker/denser clothing would give you more protection. That is covered :)

Sunscreen is what I was wondering about.

"Studies over the years have shown that sunscreen with an SPF, or sun protection factor, of 30 blocks about 97 percent of ultraviolet rays. A rating of 15 means 93 percent of UV rays are blocked, and anything higher than 30 remains in the 97 or 98 percent range" ...... "What many people do not realize is that the amount of sunscreen applied plays an enormous role. A study in The British Journal of Dermatology this year found that applying less than two ounces over the entire body at one time can leave people with an SPF rating far lower than what is on the bottle" - http://www.nytimes.c...7real.html?_r=0

I was assuming zinc oxide SPF 30 sunscreen would be an adequate form of protection, if flashing a human many times, as that is what I was going to use, along with safety-glasses for eye protection (by default. The contact lens idea was just an idea).

Was just wondering if anyone had anything better to recommend, or if they think taking pictures of people with their eyes closed with sunscreen applied to their lids and rim would be safe.

Will be waiting to see any responses.

Edited by Pylon, 22 November 2015 - 21:45.


#30 Andrea B.

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Posted 22 November 2015 - 23:54

You will get some pretty weird portraits of these goggled, sunscreened people.
Go look in our Portrait section to see what sunscreened people look like.
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#31 lost cat

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Posted 23 November 2015 - 01:25

I'm new here but I'd like to chime in.

I have been taking UV portraits and have worked with very strong UV lasers, both puilsed and continuous wave so the question of safe UV exposure is of interest to me. For my portrait work I use a pair of 26W CFL blacklight blue bulbs for illumination. The bulbs are about 1.5m away from my subject (usually me) and are about 25% efficient. This yields about 13W of actual UV power from the bulbs ranging between 325nm to 405nm peaking at around 365nm. Assuming the reflectors are 100% efficient (a big assumption) and based on my experience with the reflectors with visible incandescent bulbs the reflected intensity is not strongly focused I estimate the intensity of the lights in the focal plane to be <1W per square meter. A 1s exposure is sufficient for a good image with an unmodified Nikon D40. I would assume a camera modified for full spectrum would need even less.

Regarding fluorescent blacklights a quick look at the spectrum of these bulbs (attached) shows they are a nearly ideal source for UV photography, e.g. lots of UV with negligible visible light and no IR.

I would suggest anyone concerned about exposure to continuous wave light sources during setup use a shutter or curtain to block the UV source except for the few seconds its needed.

Regarding adequate eye protection I have tested my prescription eyeglasses in a spectrophotometer. I found they transmitted negligible amounts of UV. Polycarbonate itself is great at absorbing UV light (see attched spectrum) and I imagine any AR and antiscratch coatings on eyeglasses can only help block UV. Polycarbonate safety glasses can be an option for those who don't wear prescription glasses.

Attached Images

  • Attached Image: 352nm BLB.jpg
  • Attached Image: 368nm BLB.gif
  • Attached Image: polycarbonate.gif


#32 enricosavazzi

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Posted 23 November 2015 - 08:33

View PostJCDowdy, on 09 November 2015 - 16:26, said:

As UVP's resident photobiologist and UV photosafety expert I have been meaning to open a posting on this topic and I apologize for not finding the time to take the lead on this. There are many variables to consider some of which are mentioned above and some of which I have commented upon from time to time.
[...]
John,

I found a few brief mentions of the fact that the exposure time to UV (in addition to the total amount of UV radiation, i.e. time x intensity) affects the biological risk. Some of these information sources (mostly Internet, and I was unable to find any "hard" references) state that some organic macromolecules can be damaged by a one-photon UV strike, but recover (i.e. repair themselves, perhaps by reforming the temporarily broken atom-to-atom links, or are repaired by cellular mechanisms) within a short time. If a second UV photon strikes the molecule at a critical position before the first damage is repaired, the cumulative damage may be beyond repair.

If confirmed, this may mean that exposure to UV xenon flash is far more dangerous than exposure to the same amount of UV emitted by a lower-intensity continuous source over a longer time. This also depends on the time required by these molecules to repair. If it takes minutes or longer, then it probably does not matter whether the UV source is flash or continuous, in the conditions we normally use to record UV images (our exposures are typically less than a minute). If it takes milliseconds or less, then it does matter whether we use flash or a continuous source.

Are you aware of any reliable references to this behavior of organic macromolecules?
-- Enrico Savazzi

#33 Andrea B.

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Posted 24 November 2015 - 00:13

Lost Cat (name??) --

Go to the beginning of this topic and read the information about Recommended Maximum UV Exposure and Eye Damage from UV Exposure.

No human subject should be sitting for a UV portrait under artificial UV illumination of any kind for any amount of time.
UV eye damage is cumulative and not repairable.

Especially do not damage a child's eyes from any exposure to artificial UV illumination because children's eyes have not yet been able to build any yellowing of the cornea to block harmful UV and violet rays. Artificial UV illumination is even harder on young eyes than on old ones.

Anyone who feels the necessity to make UV portraits should simply take their subject out into the sunlight. Yes sunlight has its risks, but so much less so than from artificial UV illumination.

Also note that if your prescription glasses do not wrap around your eyes, then they are not sufficient protection. You will receive a lot of UV from reflections which enter at the side of your glasses. And you can't see it comin' so you don't even know it is happening !!

You have estimated the UV light intensity on the focal plane to be 1 Watt/m2. What is needed is the UV light intensity on the human subject at a distance of 1.5 meters ?? Then you can use the recommendations above to calculate the maximum exposure time for an 8 hour day.

However, just because there is a recommended exposure time does not mean that there is no damage done by artificial UV illumination. I think this is the part which is missed by everyone. We calculated above that maximum exposure to a Blak-Ray B-100 lamp at a 5 cm distance is 46 seconds within an 8 hour day. That does NOT mean that those are 46 safe seconds. They are not. UV damage is cumulative.
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#34 Cadmium

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Posted 24 November 2015 - 01:39

UV light is dangerous. The posted contact lens pic does nothing to make it look safe to me, in fact that pic looks to me like the contact transmits UV, and only covers part of the eye.
Glasses and contacts may be designed to block UV from sunlight to whatever extent, but they are not designed for intensities from torches, flashes, etc..

I have also seen posts about UVC sterilization bulbs, which are designed to kill, that is what they are for. They have strict warning labels on them, they are used inside of self contained compartments to kill things.
So if you use those, wire it all up so you are in another room, and make sure there are not pets or living things in the room you shoot UVC!
Any exposure to UVC should be out of the question.

So as public posts, these ideas should not be played around with for people who may read part of these ideas and then go lighting their homes and their eyes (skin even) with UV .
You are worth more than any photography hardware.
Just my 2 cents that I was trying to save for a UV-Nikkor.

Outdoor light works just fine for me when it comes to faces.

Edited by Cadmium, 24 November 2015 - 02:48.


#35 lost cat

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Posted 24 November 2015 - 09:54

Lost Cat (name??) --

Jim

Go to the beginning of this topic and read the information about Recommended Maximum UV Exposure and Eye Damage from UV Exposure.

I did. I also have many years of experience working with very high intensity UV lasers. I don’t take UV exposure lightly.

No human subject should be sitting for a UV portrait under artificial UV illumination of any kind for any amount of time.
UV eye damage is cumulative and not repairable. Especially do not damage a child's eyes from any exposure to artificial UV illumination because children's eyes have not yet been able to build any yellowing of the cornea to block harmful UV and violet rays. Artificial UV illumination is even harder on young eyes than on old ones.

Which is why I have my subjects close their eyes or wear eye protection when exposed to UV

Anyone who feels the necessity to make UV portraits should simply take their subject out into the sunlight. Yes sunlight has its risks, but so much less so than from artificial UV illumination.

Sunlight is far more UV intense than at least my artificial portrait lights. Please see below

Also note that if your prescription glasses do not wrap around your eyes, then they are not sufficient protection. You will receive a lot of UV from reflections which enter at the side of your glasses. And you can't see it comin' so you don't even know it is happening !!

Depends. If the UV light comes mainly from one direction – direct line of sight from the lamps – eyeglasses should indeed provide adequate protection as the eyes will be in the “shadow” of the lenses. Far more protection than when outdoors where reflective surfaces are much less controllable.

You have estimated the UV light intensity on the focal plane to be 1 Watt/m2. What is needed is the UV light intensity on the human subject at a distance of 1.5 meters ?? Then you can use the recommendations above to calculate the maximum exposure time for an 8 hour day.

Perhaps I misused the term. I meant the plane my cameras are focused on which is also the position of my subject (again usually me). This plane is 1.5 meters away from the lamps so it receives in my estimation less than 1W/m2. The sun delivers 1120W/m2 of light to the surface of the earth of which 3-5% is below 400nm or about 34-56W/m2 a portion of which is UVB and UVC neither of which are produced by my BLB lamps:

https://en.wikipedia.org/wiki/Sunlight

As far as UV intensity goes I'll take my 0.9W/m2 lamps over the 34-56W/m2 of the great outdoors any day. At least for the few seconds it takes to snap the shot.

However, just because there is a recommended exposure time does not mean that there is no damage done by artificial UV illumination. I think this is the part which is missed by everyone. We calculated above that maximum exposure to a Blak-Ray B-100 lamp at a 5 cm distance is 46 seconds within an 8 hour day. That does NOT mean that those are 46 safe seconds. They are not. UV damage is cumulative.

No argument there – the Blak-Ray B-100 you mention uses a 100W fluorescent lamp, which is 2x stronger than my 2x26W lamps at a working distance 30x closer (5 cm vs. 150 cm), yielding an overall intensity 1,800x greater.
I should mention I am hoping to use my portraits as a tool to convince people of the need to use sun protection and perhaps track skin damage with age. If sitting under my relatively meek UV lights for a few seconds convinces someone to wear sun protection for the rest of the day I think overall that's a win.

Edited by lost cat, 24 November 2015 - 10:03.


#36 Andrea B.

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Posted 24 November 2015 - 14:46

Which is why I have my subjects close their eyes or wear eye protection when exposed to UV

Jim - thank you, thank you, thank you for supporting responsible Artificial UV Illumination !!!! :lol:
You have eased my mind.

Recently I felt as though I was becoming the Artificial UV Illumination Police with all my attempts to warn naive users of UV lamps/flashes/torches/bulbs about the dangers they might encounter or the harm they might do. It is difficult to maintain a website for UV photography sometimes because there is some inherent danger in the lighting aspects of the art, so we must provide warnings. I'm happy to know that you - along with our bio guy John Dowdy - can help me with this effort.

I would still suggest a pair of wrap around UV-block goggles. The UV light entering behind glasses might not hit your pupil, but can still damage the conjunctiva. Edmund Optics makes a pair of UV-blockers with vents for cheaps. They are real cute and provide the wearer with a space alien look.
Andrea G. Blum
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#37 lost cat

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Posted 24 November 2015 - 17:33

View PostAndrea B., on 24 November 2015 - 14:46, said:

Which is why I have my subjects close their eyes or wear eye protection when exposed to UV

Jim - thank you, thank you, thank you for supporting responsible Artificial UV Illumination !!!! :lol:
You have eased my mind.

Recently I felt as though I was becoming the Artificial UV Illumination Police with all my attempts to warn naive users of UV lamps/flashes/torches/bulbs about the dangers they might encounter or the harm they might do. It is difficult to maintain a website for UV photography sometimes because there is some inherent danger in the lighting aspects of the art, so we must provide warnings. I'm happy to know that you - along with our bio guy John Dowdy - can help me with this effort.

I would still suggest a pair of wrap around UV-block goggles. The UV light entering behind glasses might not hit your pupil, but can still damage the conjunctiva. Edmund Optics makes a pair of UV-blockers with vents for cheaps. They are real cute and provide the wearer with a space alien look.

Glad to hear it. I do hope though that we can keep the caution to a reasonable level without crashing into an abyss of hysteria. Humans, at least the ones I know are not like vampires, disappearing into a pile of ash when touched by a beam of sunlight. Most humans CAN tolerate a dose of UV now and then; indeed, according to the World Health Organization its actually good for you:

Posted Image

http://www.who.int/uv/health/en/

I suppose if it makes one feel better one can limit artificially lit UV portraiture to winter months when environmental UV exposure is minimized.

#38 Andrea B.

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Posted 24 November 2015 - 22:53

Skin fine. Eyes no.

Anyway, I'm only slightly hysterical on alternate Thursday afternoons between 3 and 5 PM about UV in the eyes. It's just that I had 4 eye surgeries on my left eye from a double cataract and consequent complications. No fun.

My lens implant blocks UV (of course) and some of the "bad" violet and blue. Interestingly, with the left eye I can detect some spectral violet leak from one of my 365nm UV-LEDs. I only just realized this recently. But not so with the right eye which still has the aging, yellowed cornea which we all develop. Also blue looks bluer with my left eye and more cyanish with my right. We do not detect this loss of truly blue blues as it is happening over the years. I cannot detect UV at all and do not want that particular superpower.
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#39 JCDowdy

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Posted 25 November 2015 - 04:05

View Postenricosavazzi, on 23 November 2015 - 08:33, said:

John,

I found a few brief mentions of the fact that the exposure time to UV (in addition to the total amount of UV radiation, i.e. time x intensity) affects the biological risk. Some of these information sources (mostly Internet, and I was unable to find any "hard" references) state that some organic macromolecules can be damaged by a one-photon UV strike, but recover (i.e. repair themselves, perhaps by reforming the temporarily broken atom-to-atom links, or are repaired by cellular mechanisms) within a short time. If a second UV photon strikes the molecule at a critical position before the first damage is repaired, the cumulative damage may be beyond repair.

If confirmed, this may mean that exposure to UV xenon flash is far more dangerous than exposure to the same amount of UV emitted by a lower-intensity continuous source over a longer time. This also depends on the time required by these molecules to repair. If it takes minutes or longer, then it probably does not matter whether the UV source is flash or continuous, in the conditions we normally use to record UV images (our exposures are typically less than a minute). If it takes milliseconds or less, then it does matter whether we use flash or a continuous source.

Are you aware of any reliable references to this behavior of organic macromolecules?

Enrico,

Well, where to start.

The concept you are referring to is photobiological reciprocity which basically says that a photo effect is dependent on the exposure dose (intensity x time) but not the intensity or time alone.

10 Joules/unit area = 1 Watt/unit area x 10 seconds = 10 Watts/unit area x 1 second

However, in complex biological systems where there are often multiple chromophores, overlapping reactions and repair mechanisms true reciprocity can only exist over a finite dose range, if at all.

An accessible resource is the free online textbook Photobiological Sciences Online (http://www.photobiology.info/) posted by the the American Society for Photobiology (ASP). I would suggest the module on Biological Action Spectra in the Spectroscopy chapter, specifically the section heading Reciprocity Should Hold. Also, the module Basic Ultraviolet Radiation Photobiology in the UV Radiation Photobiology chapter gives an overview of the complexity.

In one sense when UV damage or injury occurs it is a form of reciprocity failure, at least from the perspective of maintaining homeostasis. On the other hand, threshold injury responses, such as sunburn, do generally follow a dose reciprocity rule within a limited time frame.

The intensity required to enter into more exotic multiphoton photoexcitation is a good bit higher than is achievable with photographic strobes as far as I am aware. Normal UV repair processes are not as fast as a strobe or even a short exposure to a continuous source but strobes can accumulate high doses faster if repeatedly pulsed.

I am actually more concerned with the unnecessary short wavelengths present in unshielded quartz Xe strobes. Same as with a continuous source, shorter more energetic wavelengths are generally more hazardous. I am considering filtering a UV modified flash with a Schott WG-320 or WG-305 in order to better reproduce the UV spectral balance of sunlight and reduce the risks from shorter wavelengths.

#40 Bill De Jager

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Posted 25 November 2015 - 04:55

View PostJCDowdy, on 25 November 2015 - 04:05, said:

I am actually more concerned with the unnecessary short wavelengths present in unshielded quartz Xe strobes. Same as with a continuous source, shorter more energetic wavelengths are generally more hazardous. I am considering filtering a UV modified flash with a Schott WG-320 or WG-305 in order to better reproduce the UV spectral balance of sunlight and reduce the risks from shorter wavelengths.

Thanks for the product names! I have a couple of units with these quartz tubes. Though I haven't used them yet, I've been concerned about incidental exposure - both to me and to the surroundings. UV goggles are one thing but full-body protection (and protection of any sensitive materials in the same room) would be a lot more hassle. I don't want to mess around with UV-B or UV-C!

Edited by Bill De Jager, 25 November 2015 - 04:56.