[UV SAFETY] UV and Your Eyes :: UV Safety Reference

November 6, 2015

Last Edit [22 July 2021: Added links to other pinned UV Safety topics.]

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See also:

Ultraviolet Keratitis
This is a medical monograph by Reed Brozen, MD at Dartmouth Medical School,
Dartmouth-Hitchcock Medical Center, Vermont.
Corneal Flash Burns

Long term exposure to UV from sunlight or other sources causes cumulative damage to the human eye which typically manifests itself as the formation of cataracts. A cataract is a cloudy deposit on or within the eye lens. It is said that sooner or later we all get cataracts. This is why ophthamologists encourage everyone to wear UV-blocking sunglasses when outdoors. Long term exposure to UV in sunlight or from other sources can also cause retinal damage or eye cancers.

These links about cataracts and UV are from the US National Institute of Health:

Sources of UV Light

Halogen lights, carbon arcs, welding arcs, sunlight, sunlight reflected on snow, sunlight reflected on water, UV-flashes, photo floodlights, sun lamps, tanning beds, UV-LED torches/flashlights, UV-C sanitation devices, UV lamps, UV fluorescent tubes.

UV Exposure Recommendations

The Columbia University (New York City) monograph Working Safely with Ultraviolet Radiation contains some UV exposure recommendations listed below. Columbia University also notes that in the United States there is no Occupational Safety and Health Administration (OSHA) standard for exposure to ultraviolet light. (OSHA is a federal agency in the US Department of Labor which enforces safety & health laws.) However, the National Institute for Occupational Safety and Health (NIOSH), part of the US Center for Disease Control and Prevention, does make some recommendations. Also, the American Conference of Governmental Industrial Hygienists (ACGIH) has issued Threshold Limit Values (TLVs) for occupational exposure to UV.

I have to review notation here so I can keep it straight.

watts = W

milliwatts = mW

microwatts = µW

1W = 10³mW = 10⁶µw

meters = m

centimeters = cm

1m² = 10⁴cm²

Columbia University Recommendation for UV-A Exposure in Wavelength Range 315-400 nm

10 Watts/m² for every 1000 seconds.
In words, the maximum time for unprotected exposure of skin/eyes
to a UV-A irradiance intensity of 10 Watts per square meter
should not exceed 1000 seconds.

ACGIH Recommendation for UV-A Exposure in Wavelength Range 315-400 nm

1 milliWatt/cm² for every 1000 seconds
In words, the maximum time for unprotected exposure of skin/eyes
to a UV-A irradiance intensity of 1 milliWatt per square centimeter
should not exceed 1000 seconds.
This is (obviously) the same as the preceding Columbia recommendation.
- 10 Watts/m² = 1 milliWatt/cm²
- 1 milliWatt/cm² for 1000sec == 1000 milliWats/cm² for 1 second.
- Thank you, Metric System.

Columbia Recommendation for UV-B Exposure in Wavelength Range 200 - 315 nm

It appears to me that this range includes some UV-C, yes?

The radiant exposure on unprotected eyes and skin within any 8 hour period is limited to values which depend on the wavelength of the radiation. For a broadband source the effective irradiance should be measured or calculated, and the maximum permissible exposure determined from the table below.

LEFT: Effective Irradiance (Watts/m²)
RIGHT: Maximum Permissible Exposure during an 8 hour period
- 0.001 8 hours
- 0.008 1 hour
- 0.05 10 minutes
- 0.5 1 minute
- 3 1 second
- 30 0.1 second

NIOSH Recommendation for UV-C Exposure at Wavelength 254 nm

Note that 254 nm is the typical wavelength for UV-C sanitation lights.

100 μW/cm² for 1 minute
In words, the maximum time for unprotected UV-C exposure of skin/eyes
to an intensity of 100 microWatts per square centimeter should not exceed 1 minute.
When averaged over an eight-hour work day, this value is 0.2 microWatts per square centimeter.
Convert: 100 microWatts/cm²= 0.1 milliWatts/cm² for 1 minute.
Convert: 6 milliWatts/cm² for 1 second.
Obviously, the greater the intensity of the UV-C light source, the shorter the time
you are allowed for unprotected exposure.
In case this is not hitting home with you, the NIOSH recommendation is telling you that
254 nm UV-C light is extremely dangerous !!!

Side Note: There is one incomplete statement in this Columbia U. reference. They say eye damage is from UV-B and UV-C, but it has been recently learned that eye damage also occurs due to oxidative stress from UV-A. See Ultraviolet Keratitis link above.

Example: Blak-Ray B-100 AP Lamp

From the manufacturer's data, we have that the Blak-Ray B-100 AP lamp with a UV-A range peaking around 365 nm delivers an intensity of 21.7 milliWatts/cm² at 5 cm (about 2 inches) and 8.9 milliWatts/cm² at 25 cm (about 10 inches) distance from the lamp.

Various factors affect the actual intensity from such a lamp because of geometry, angles of use, ambient reflections and so on. Nevertheless, we will use those numbers in the following model as a worst-case intensity from a Blak-Ray directly shining on a subject.

Given that the Columbia or ACGIH recommendation for UV-A is 1000 milliW/cm²for 1 second,

we can convert to get an exposure time for the Blak-Ray lamp of 1000/8.9 = 112 seconds = 1.87 minutes. (This does make the assumption that the Blak-Ray lamp is only outputting UV-A. The Blak-Ray also outputs some UV-B, but we are ignoring it just to get an estimate.)

So, within an 8 hour day you only have a little under 2 minutes without protection to safely(?) experience UV-light from a Blak-Ray B-100 lamp at a distance of 25 cm (10 in)

If you have the Blak-Ray shining directly on yourself at the closer distance of 5 cm (2"), then within an 8 hour day you only have a recommended exposure time of 46 seconds.

Wear your UV-blocking goggles.

And remember that even if you should one time escape obvious UV keratitis of your cornea when looking at UV-light with no eye protection, the UV damage to eyes and skin is cumulative.

Eventually UV-light will getcha if you don't protect yourself!

And now for a musical interlude:

Start at 52 seconds in.

UVA-in-Sunlight vs. the Blak-Ray B-100 Lamp

Reference: Incoming Sunlight from NASA Earth Observatory

All radiation from sunlight is equivalent to an intensity of 1.36 kiloWatts/m² at the distance from sun to earth. That translates to 136 milliWatts/cm² at the distance from sun to earth.

Convert: 1kW = 10⁶mW (milliWatts)
Convert: 1m² = 10⁴cm²

Of course, this total solar irradiance figure must be modified by reference to geometry, angles, atmosphere and so on when used in any model. Nevertheless, we'll use the 136 milliWatts/cm2 value in the following little estimate as a worst-case kind of intensity from a presumed directly perpendicular ray of sunlight hitting an arm on the ground.

At ground level sunlight consists of about 3% UV. So, UV-in-sunlight has an approximate intensity of (136)(.03) = 4.08 milliWatts/cm² at the distance from sun to earth.

From the preceding section, we have that the Blak-Ray lamp has an intensity 8.9 milliWatts/cm² at a distance of 25 cm (10 in).

On a good strong sunny day, put your right arm on the ground and put a Blak-Ray lamp about 25 cm (10 in) away from it. Now put your left arm on the ground. In your current awkward position, the Blak-Ray lamp intensity at 10 inches from your right arm is approximately twice that of the UV-in-sunlight reaching your left arm.
8.9/4.08 = 2.18
Make sure you are wearing your hat and sunglasses when you perform this arm-burning experiment.

Your right arm which is 10 inches under that Blak-Ray lamp will be good for about 112 seconds, a little under 2 minutes, before sunburning begins. Your left arm will be in the sunlight for about 245 seconds = 4.08 minutes before it begins to fry.

If your Blak-Ray lamp is placed about 5 cm (2 in) inches from your arm, then the Blak-Ray intensity at 2 inches from your arm is approximately 5 times that of the UV-in-sunlight reaching your arm.
21.7/4.08 = 5.3

Please don't mess around with your Blak-Ray lamps by shining them in anybody's eyes or skin, whether human or animal.

UV-C @ 254 nm vs. the Blak-Ray Lamp

From above, recall the approximations for unprotected exposure lengths.

60 seconds for the 254 nm UV-C source at a distance which produces the intensity 0.1 milliWatts/cm².
112 seconds for the Blak-Ray Lamp at 25 cm distance with intensity 8.9 milliWatts/cm.
- Convert UV-C: 0.1milliWatts/cm² for 60 sec = 6 milliWatts/cm² for 1 second.
- Convert Blak-Ray: 8.9 milliWatts/cm² for 112 sec = 996.8 milliWatts/cm²for 1 second @ 25cm distance.

During a 1 second interval, you could be safely(?) exposed to 166 times more Blak-Ray light than UV-C light. I hope that I have stated that sensibly. The point is that UV-C is quite dangerous when compared to the usual mostly UV-A illumination and it takes very, very little time before UV-C damage begins.

I would like to have the numbers for an actual UV-C device to better make the point here.

I would also like to have the numbers for one of the 365 nm UV-LEDs so I could make similar comparisons.

Whatever I'm missing here (aside from a few UV-fried brain cells), please let me know and I'll correct it.

Thanks!

November 8, 2015

Andrea, "distance not given" should not matter. These recommendations should be for the amount of radiation received by the target surface. It's up to the user of these recommendations to either measure the UV flux directly at the effective distance, or else calculate the effective flux given the distance involved and the emissivity of the source. The latter may be tricky as I don't think that light modified by a curved mirror or a lens *necessarily* follows the inverse square law in all cases. I hope someone who knows more on this can chime in.

November 8, 2015

Bill, thank you for reading this!

I probably should not admit just how long it has been since I dealt with anything from the land of physics (very long time ago). Later the penny did drop, and I realized what you said about distance. In the referenced thread (How Much UV is Bad for Me), I noted that I was also unsure about application of inverse square law. And still am. :rolleyes:

My hope is that I have translated the Blak-Ray data acceptably according to the NIOSH & ACGIH rules so that any photographic user of UV-flash, UV-lamps and/or UV-LEDs gets the idea that eye protection is mandatory and skin protection useful for the UVA/UVB range.

Note: I am cleaning up the first post so that it reads more easily.

November 9, 2015

One complication is that different wavelength ranges carry different kinds of hazards. The shortest wavelengths have little penetrating power and produce damage primarily on outer surfaces (some cannot even penetrate far into film emulsion.) Longer wavelengths are more insidious because they penetrate to greater distances and are more able to do subsurface mischief. Short-wavelength visible light (<500 nm) is itself known to have ionizing potential and can contribute to skin aging and carcinogenesis, among other things.

November 9, 2015

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.

In my profession I rely primary on the following organizations providing guidance and safety standards on optical radiation safety:

IESNA (Illuminating Engineering Society of North America) which has adapted and expanded the older ACGIH (American Conference of Governmental Industrial Hygienists) guidance. The IESNA is an ANSI accredited standards developer and their relevant work is published an an American National Standard in the multi volume ANSI/IESNA RP-27 series of Recommended Practice for Photobiological Safety.

CIE (Commission Internationale de l'Éclarage -or- International Commission on Illumination) Division 6 Photobiology and Photochemistry, has adopted much, but not all, of the IESNA work and has published jointly with the IEC (International Electrotechnical Commission) the international standard CIE S 009 / E:2002 / IEC 62471:2006.

The two most critical factors to consider for exposure to continuous sources are the spectral distribution and exposure dose. The spectral distribution, or spectral irradiance is considered against several weighting functions representing different spectral hazards. For eye and skin the UV risk from shorter UV wavelengths may be several orders of magnitude greater than from longer UV wavelengths. The exposure dose is of course a function of the power of the source and the exposure time. For pulsed sources, such as our modified photographic strobes the dose is a function of pulse duration and number of pulses within a certain time.

I am not yet prepared to offer formal recommendations on limits for photographing human subjects. However at this point I am strongly cautioning against use of modified strobes and continuous UV sources to photograph people who are without proper eye protection.

I will also caution UV photographers to be mindful of radiation reflected and scattered back upon themselves, especially when using modified strobes, continuous UVB and UVC (germicidal) lamps. A UVC lamp can injure within seconds, a UVB lamp within seconds to minutes and a UVA lamp in minutes to hours depending on exposure dose (power x time) so the use of proper shielding and preferably remote camera operation is advised and in some cases may likely be required.

November 9, 2015

John, thank you so much for this excellent commentary on UV photosafety.

I have taken the liberty to embolden two parts of your post so that readers "take it home" that UV light is dangerous.

In the UV Sticky, I am going to link to this topic.

FWIW, my personal opinion is that no UV photographer should be attempting to photograph with UV-C light.

November 9, 2015

I have wanted to respond to this from the beginning........but this is the best I can do diplomatically....

Whatidiot would argue about personal safety, particularly your eyesight, then go & put someone else in danger of damaging their eyesight!

Col

November 10, 2015

John, How do you feel about the common variety black light? People often buy them to illuminate various things in homes, displays, parties, etc..

I have seen these illuminated for sale in stores. I have used them for UVA photography, and tested them with bandpass filters, and they emit a much wider and deeper range of UV than just 365nm,

mine strongly illuminates a 325BP10 band pass filter, and my entire range of UV bandpass filters upward.

These are readily available everywhere with no warnings about their use as far as I have seen, and I think most people consider them 'safe'.

I have one here in front of me, a compact fluorescent type, purchased at a hardware store, it has no warnings on it, I caution everyone I know about these common UV lights.

These are UV lights, and they should be treated as such, and I am wondering if there should be stronger warnings about their use.

November 10, 2015

But NO UV light is safe !

The SUN is NOT safe !

The disco / party lights are NOT safe, they are at a distance though & the atmosphere / distance, will cut some UV.

Safety has all levels of safe & danger !

Some happen immediately / instantly, so you are very aware.

Some have a time factor, minutes, hours, days....& lifespan limiting.

So because it doesn't happen immediately, why is there debate about how safe / unsafe, something is ?

Are the doubters that DUMB !

Why does it even need to be debated, it is a no brainer, DON'T FRIGGEN DO IT !

Col

November 10, 2015

Col, No debate, simply pointing out that I think common black lights may be more dangerous than commonly thought of by most people, and should carry warnings.

Those lights are used in all sorts of ways, close and far, and some people probably stare at them in close proximity. So no, I don't think they are 'safe'.

November 10, 2015

No offense intended Steve, I was responding to the thread in general & particularly the doubters ;-)

Col

November 10, 2015

........ I think common black lights may be more dangerous than commonly thought of by most people, and should carry warnings.
Those lights are used in all sorts of ways, close and far, and some people probably stare at them in close proximity. So no, I don't think they are 'safe'.

A good question.

The safety standards have a classification scheme which includes an 'Exempt' class. As the name implies products in the 'Exempt' class are exempted from label warning requirements. This does not mean that an 'Exempt' source is totally without measureable 'Hazard', only that the probable 'Risk' from that 'Hazard' is deemed by competent authorities to be acceptable. In this context 'Hazard' is best understood as a source of potential injury and 'Risk" is the likelihood that exposure to a hazard will result in injury to a normal person.

The methods, in the testing standards I mentioned, specify measurement distances depending on the nature of and assumed use of a source. Misuse of a source, such as staring at a black light in close proximity, is therefore not the legal responsibility of the product manufacturer. A toothbrush manufacturer is likewise not responsible if you poke it in your eye.

The pertinent question must then be, is the use of a black light for UV photography an assumed, normal or predictable, use of the source? The black light you show above has a standard medium base which will fit the socket in an overhead room light or a free standing lamp of some sort. The presumed use is for the excitation of fluorescence in objects for aesthetic reasons, the stereotypical black light poster for example. However, the measurement required is 20 cm on a bare lamp. If you are closer and/or put that lamp in a reflector and/or use more than one bulb and then point it into someone's face you could exceed the assumed conditions of exposure which permitted the exemption from label warnings.

All of what I just said presumes a source was actually properly tested and that the jurisdiction in which it it was manufactured or sold is aware of or concerned about photobiological safety standards.

November 10, 2015

Col, while I appreciate your enthusiasm in getting the word out that UV light is dangerous, remember that not everyone actually knows that! So we must let the questions be asked and then provide a responsible answer. :)

Cadmium's question, for example, now prompts me to go into the Sticky and the first post and add a remark about the UV "party lights" which are so commonly used.

November 15, 2015

We can only do so much in pointing out the inherent danger of dealing with UV light sources. Let's applaud Andrea for her efforts and hope people understand the need for protecting themselves. Enlightening and educating people assume there are senders and receivers of information.

November 19, 2015

I have contact lenses that say they are uv-blocking.

I took a shot of my eye using a UV flash attached to the hotshoe of my camera:

Using contact lenses, do you think it is now safe to photograph people in UV with their eyes open?

I was also using the 199A and noticed that the power settings weren't really changing whenever I changed the right slider, or the slider that is tucked away when the flash is folded, on the front of the unit. It used to be that if the right slider was all the way down, it was at full power. Now it doesn't seem to be change.

November 19, 2015

Using contact lenses, do you think it is now safe to photograph people in UV with their eyes open?

That is an interesting question! I think that probably the answer is likely to be "NO" unless you have very specific information about the brand and type of contact lenses. Here are 3 reasons why.

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.

Here is a reference from the American Optometric Association about contact lenses & UV protection: UV Protection with Contact Lenses

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.

OK, get the picture now?

Yes, you finally got your UV eye picture above. There were no surprises. So stop UV flashing your eye so that I won't have to use you as the Bad Example in a couple of years when you are being rolled into the operating room for eye surgery.

All you really need to do is go outdoors in good sun and take a UV selfie. Much safer.

Why not go take some useful UV photographs of anything except living eyes and provide us with some interesting forensic examples? Please.

November 19, 2015

http://www.msn.com/en-au/health/medical/what-uv-light-does-to-skin-to-cause-sunburn-wrinkles-and-cancer/ar-BBn9cZK?li=AA4RDf&ocid=iehp

UV light causes everything from sunburn to skin cancer and the wrinkles and sagging that come with age. But what exactly does it do in our bodies to wreak all that havoc?

Ultraviolet (UV) light is just a higher energy version of the light we see (visible light). And it's that higher energy that makes the UV in sunlight damaging to our cells and tissues.

To do any damage, UV light has to be absorbed. This happens at the molecular level. And it happens one electron at a time.

When a single electron absorbs a photon of UV light, that electron goes into a higher energy state. An excited electron like that makes a molecule behave in different ways — sticking to things it shouldn't stick to, changing shape, and generally messing with normal healthy cell business.

Luckily we evolved in a world that's saturated with UV light, so our cells have built-in repair kits for the damage UV radiation can do. But if the damage outweighs our capacity to repair, or our repair kits themselves get damaged, it's hello liver spots, cataracts and — way too often — skin cancer.

There are two kinds of UV radiation in sunlight — UVA and the higher energy UVB. And the trouble starts when they're absorbed by our more important molecules — DNA, RNA or proteins.

The pain. The heat. The redness. The judgemental looks from everyone who thought to dress appropriately.

They're all part of the sunburn experience. And — judgemental looks aside — they are all caused by UVB radiation.

Sunburn is the body's way of healing from the damage caused by UV radiation. It's your standard inflammation to clear away damaged cells, plus a little pain.

Like all inflammations, it involves a bunch of messenger chemicals (cytokines) signalling for more blood to be delivered (causing redness and heat) and more white blood cells to clean up the mess. And the whole thing can be kicked off by UV damage to a single molecule — a small bit of RNA called U1.

When a photon of UVB hits U1 RNA in the nucleus of a cell, it changes the RNA's structure. That tiny tweak is enough to kick off the whole heat-redness sunburn cytokine festival.

The pain part of sunburn is down to one particular messenger molecule, CXCL5. It attracts white blood cells into the skin's dermal layer, activating pain fibres there.

So it's CXCL5 that makes us sensitive to pain for a couple of days after the event, which has made it a 'molecule of interest' for pharmaceutical companies looking for new pain-relief drugs.

If you've had a skin cancer frozen off or cut out, you can blame kinky, mutant DNA caused by UVB light.

Somewhere back in your past, a photon of UVB made two bits of your DNA that are next to one another stick together (a couple of thymines, or 'T's in DNA code).

With those two T's stuck together, that stretch of DNA suddenly had a kink in it. Like a zipper with a broken tooth, the kink distorts the shape of the DNA in that cell, making it harder for your cell's enzymes to read and copy it properly.

Luckily we've got an entire molecular system devoted to finding and fixing these kinks. More than 30 proteins work together to replace the affected DNA. It's an incredible system, but it's not foolproof, so over time you can get a build-up of missed errors.

Errors in DNA are mutations, and if those mutations affect the cell's ability to keep itself in check (like a mutation in a tumour-suppressing gene), you can get the kind of out-of-control growth of cells that make up a skin cancer.

Worse still, if the mutation happens in a melanocyte (the skin cells containing the brown pigment melanin that colours our freckles, moles and tans) a far more dangerous cancer can result — melanoma.

Direct attacks on DNA aren't the only way UVB can cause mutations. It can also break proteins apart, and the high-energy molecules that result (radicals) are spectacular at attacking DNA.

UVA gets in on the act too by creating high-energy, oxygen-based compounds that go on a rampage, ripping other molecules apart.

Anti-oxidants in our cells do their best to soak up these destructive radicals, but it only takes one missed error in the wrong gene to need a date with your doctor and some liquid nitrogen.

The cloudy lens that makes it hard for cataract sufferers to see can also be caused by UV light.

The lens in your eye is normally clear, because the cells that make it up don't have a nucleus or other lumps to interfere with light — they mostly contain proteins, neatly aligned to let light through. But in 2014, researchers showed UVA light can trigger a chain reaction inside the lens that makes the proteins clump together, causing the cloudy look.

Our eyes have a special set of proteins, called chaperones, that work against the clumping, but if the clumping outperforms the chaperones, cloudy cataracts are the result.

While UVB is busy mutating DNA and setting off sunburn in the epidermis, UVA can penetrate more deeply into the dermis (the second layer of skin cells) where it converts firm, youthful skin to something that looks like mine.

Anyone who's spent more than $10 on a beauty product knows the key to firm skin is a protein called collagen. It comes in long fibres that form a mesh, giving structure to our flesh.

UVA doesn't directly attack the collagen, it's sneakier than that.

UVA activates receptors that produce the enemy of firm skin: matrix metalloproteinases. These enzymes have one job and they do it beautifully: breaking down collagen. And it doesn't take much UV at all to get this going, so even without sunburn any parts of your skin that are exposed to the sun will age.

As if the collagen attack wasn't insult enough, UV radiation also interferes with the production of Vitamin A receptors on our skin cells.

Vitamin A is critical for cell growth in our skin, but without functioning receptors for the vitamin to activate, our skin ends up thinning, and that's something no amount of carrots can fix.

November 20, 2015

Tiresome oversimplification and incorrect statements, MSN dot com is simply not a credible source.

November 20, 2015

It would be useful to know specific incorrect statements?

At least this MSN article does warn people of the UV dangers.

November 20, 2015

the original is from ABC science, written by a Bernie Hobbs, and with " thanks to Assoc Prof Terry Walsh, Head of School - Biomedical Sciences, QUT":

http://www.abc.net.au/news/2015-11-18/how-uv-light-damages-our-skin/6856742

November 20, 2015

...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).

November 22, 2015

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.

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http://ultravioletphotography.com/content/uploads/monthly_11_2015/post-79-0-37934000-1447903712.jpg

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.

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.

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).

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

November 22, 2015

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 ;-) )

November 22, 2015

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)

November 22, 2015

Thanks, Alaun.

We have elsewhere posted some links to such health and safety directives.

[UV SAFETY] UV and Your Eyes :: UV Safety Reference

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