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UltravioletPhotography

Advice needed on studio flash options for UVA and B


JMC

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I need some advice please folks. I know nothing about studio flashes, and less than nothing about them for UV photography - the only flashes I have are modified speedlights.

 

I'm looking to get a pair of flashes for UV imaging. I'd like to be able to use them for UVB and UVA imaging (not of skin I hasten to add, especially the UVB). So I'm looking for good output down to 280nm.

 

I've read that Birna uses Broncolor, Ulf uses Godox. But I guess both of these need new, non-standard flash bulbs for optimum UV imaging to produce the right spectra.

 

Are there any options for UV flashes which wouldn't require me to buy additional flash bulbs and modify them to fit the flash heads?

 

Key considerations for build quality and reliability, and consistency of flash intensity, over cost. Availability in the UK would also be preferred. Any advice welcome.

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enricosavazzi

For UVA imaging I use mostly a Bowens Gemini 500R and a Bowens Gemini 1500 Pro, both with non-coated Bowens tubes. I believe years ago I posted on UVP emission spectra of one or both. See:

http://savazzi.net/p...obes.htm#Bowens

http://savazzi.net/p...ens1500pro.html

 

Consistency of emission is very good, within 1/10 of a stop as measured with a Sekonic flash meter.

 

Bowens went out of business, so this information is only useful for legacy equipment and possibly for units from the second-hand market (although some of the units I have seen on eBay appear to have been used very heavily, possibly well past their useful life). The Bowens non-coated tubes are visually transparent and transmit UVA but essentially no usable UVB. They are not ordinary unfiltered quartz tubes because none of the relatively abundant UVB produced by quartz tubes appear in the emission spectra. This is not surprising, since they are meant to be used with human subjects. For UVB, quartz tubes are in practice obligatory, with all the problems of added need for protection of the photographer that this involves.

 

Based on a limited earlier experience, I used to think that studio strobes made in China are pure junk. I still think that most are, but Godox is different. I have a Godox AD200 and it is good, stable and relatively portable, and works well with the latest TTL Godox transmitters. I was never able to make TTL work on a Sony A7RII with first-generation Godox transmitters for Sony (the newer X Pro S does work). The first-generation Godox transmitters for Olympus work fine, instead. If I had to replace my Bowens, today I would probably choose Godox.

 

Edit: In this post I am using the "non-coated" term to indicate more clearly that the tube comes from the factory without a UV-cut coating. The "uncoated" term is sometimes used to indicate originally coated tubes that had their UV-cut coatings removed by home-made methods, which is not the case here.

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Another thing to consider is if you need a portable battery powered flash that you can use in the field or if it is sufficient with mains power only.
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enricosavazzi

Another thing to consider is if you need a portable battery powered flash that you can use in the field or if it is sufficient with mains power only.

Absolutely, this is very relevant information. I did not mention it because when one mentions studio strobes, one usually thinks of work in the studio/lab. Most studio strobes are AC powered, but several of these can be used in the field only by carrying an additional (several kg heavy) generator/battery. This is the case of the Bowens, for example. However, Godox makes a few "studio" strobes (up to 600 Ws I believe) powered by an add-on battery that clips to the main unit. The AD200 (200 Ws) is battery powered (no AC operation out-of-the-box), and its volume and weight is only about twice that of a typical largish portable camera-mounted strobe. There may be other battery-powered studio strobes of other brands, that I have not heard about.

 

PS - Another factor that may be important is that studio strobes are not designed for operation in wet or high-humidity environments - but neither are most battery-operated camera-mounted models. Water and high voltage are not a safe combination.

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Profoto and Broncolor make 'portable' (if you have the Schwartzenegger physic or a strong assistant) battery packs that can feed their A/C studio flashes.

 

I used such setups on occasion in the field, but pay proper attention to weather as studio flashes and rain don't mix well.

 

Do remember that one would not only need a quartz flash tube, but also a protection dome of quartz material as well. The latter are apparently getting a scarce item these days.

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Hmm, plenty to think about then. I hadn't even considered battery operated units. The Godox Witstro AD600pro unit is available here in the UK;

 

http://www.godox.com/EN/Products_Witstro_Flash_AD600Pro.html

 

Is it possible to tell whether this can have Quartz tubes fitted in place of the standard bulbs?

 

Birna, I hadn't even thought about the covering done for the flash tubes. Any ideas where they can be sourced from?

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According to picture#2 in the linked document, the flash tube sits enclosed in a covering dome.

 

In case one is tempted to skip the complications of a protective dome, suffice it to note that glass shards from an exploding flash can wreak havoc and cause lethal wounds. A studio flash is powerful.

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Hmm, plenty to think about then. I hadn't even considered battery operated units. The Godox Witstro AD600pro unit is available here in the UK; http://www.godox.com...h_AD600Pro.html Is it possible to tell whether this can have Quartz tubes fitted in place of the standard bulbs? Any ideas where they can be sourced from?

 

If a Godox 600Ws model is something you are aiming for now there are several models.

Godox Witstro AD600pro, Godox Witstro AD600B and Godox Witstro AD600BM all has a common Bowens mount for different reflectors and other accessories.

 

Godox Witstro AD600pro is the latest and most expensive model. It has some improvements for normal photography like a stronger modeling light and 0.9s full power recycling time.

However the battery capacity is lower. It is heavier and have a different flash bulb connector configuration.

 

All different flash tubes I have tried so far on my Godox AD200 has been possible to flash.

Only the first 40Ws type has seen problems, but it was driven 5x over its specifications.

 

I bought the tubes I tried from https://www.xenonflashtubes.com.

 

The connection of the original flash-lamps to the flash unit is done with 4mm banana-type connectors sitting mounted in a pattern in the ceramic bottom of the lamp unit.

For making the mechanical pattern of the banana connectors for my tests I use a custom-designed circuit board.

That has worked very well for the AD200 and a newly designed type fitting the older Godox models AD600B and AD600BM is under production. It will not fit the AD600pro.

 

The tube is enclosed by a glass dome that has several functions.

It might do some UV-filtering.

It is a mechanical protection against a potential tube explosion and it prevents the user from touching the tube directly as it can be very hot.

It is also a protection of the tube for handling, as some parts of the flash-tube is not mechanically very strong.

 

It is possible to fit the smaller standard reflector for AD600pro on the older models AD600B and AD600BM as it is using s Bowens mount.

That reflector is optimised for a ring flash tube looking similar to https://www.xenonfla...studio_160.html

That 1600Ws quartz flash-tube has a good power margin when used on a 600Ws flash, making overheating or explosions less likely.

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enricosavazzi
[...]

Do remember that one would not only need a quartz flash tube, but also a protection dome of quartz material as well. The latter are apparently getting a scarce item these days.

If you need a protection dome for a large straight quartz flash tube, there are third-party shields designed to surround UVC fluorescent tubes in water purifiers for aquaria or ponds. These shields are basically shaped like large test tubes, open at one end (or sometimes both ends).

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Well, I have such 'test tubes' for my aquarium sterilizers, but I don't think they are applicable here for the tubes used in these flashes.

You need actual UV transmitting versions of the 'domes' used for these flash tubes, unless your flash tube is long and straight and fits inside a long tube, then hunting for a UV sterilizer quartz sleeve will be a waist of time.

Unless someone has a specific one in mind that you know would work.

My opinion.

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Consistency of emission is very good, within 1/10 of a stop as measured with a Sekonic flash meter.

 

I measured the repeatability of my Godox AD600BM with the spectrometer.

The Godox AD600BM also give stable output levels. I saw a variation of around ±5%.

That is less than 1/10 f-stop in photography terms.

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Ok, there is obviously a lot here for me to learn about. Safety is important to me, so I'll need to figure out a way of getting a protective cover which is also UVA and B transparent. Thanks for all the information everyone.
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Actually, not sure of the size of those tubes used in the flashes above, but I suppose if they were small enough, and the quartz sleep was big enough in diameter, and you got one that was closed at one end ( 'test tube' style),

then you could possibly cut off one end, and use that. Not sure if they make one big enough for a T12 fluorescent bulb, but they probably do, so if the flash tube is no bigger around than a T12, then you might be able to do that, if you have a way to cut off the end of the tube.

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Cadmium,

Thats an interesting idea. But not really a good one. The T12 or T8 are filled with Mercury at a fixed pressure to get the desired wavelengths. A germicidal lamp is very low pressure and provides mostly 255nm mercury line. A little bit more pressure and you get the 302nm line and then medium pressure and your get the 313 and 335nm lines. The higher pressure bulbs give you the 365nm line and above.

 

Also the xenon arc lamps are filled with xenon. So you would need to fill a tube with that gas, add an arc gap and then you would be in business.

 

Interesting though on the pressure thing. Using a Lucky herb 15 UVB compact fluorescent bulb, for the first 15 minutes after turning it on I get a great 302nm line and can smell a little ozone. The ozone is probably from an initial 255nm line spike at low pressure. After the 15 minutes warm up it then gives the 313 and little 365nm lines.

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The wise admonition against omitting a protective dome has given me pause.

 

I see among the reflectors available from various makers some that accept reflector grids and color gels.

It seems that these might be suitable to support a disk of UVT acrylic.

 

Questions:

If color gels can be used without melting would clear UVT acrylic take the heat? (I think probably)

Would a 1-3mm thick acrylic sufficiently contain the shrapnel of a tube rupture? (It is fairly strong)

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Da, It was Enrico's idea, not mine. Perhaps you misunderstood.

He, and I, were not talking about using T12's, we were talking about the quartz sleeves they put the germicidal bulbs inside of (to separate the bulb from the water flowing around it).

I have no idea what the explosive resistance is of a quartz sleeve is, I was just following the thinking of Enrico.

I don't have one of the flash tubes here to measure, I have not researched the sizes, Enrico and others here who use those kinds of flashes would know the size of such flash tubes,

and I don't know the maximum size of the water sterilizer quartz tubes, and I don't know the explosive aspect of those tubes.

But I was absolutely not talking about using T12 bulbs to shroud the flash tubes. The reason I mentioned T12 is the size factor, want me to go measure one, OK, 38.10mm/1.5".

However, the largest quartz sleeve I have is not that big around, it is smaller, it holds a smaller diameter bulb, and I can't measure it at the moment because it in service.

You want to research quartz sleeves maybe? Have at it. ;-)

https://www.google.c...wiz.wNoQNU_fjos

 

The quartz sleeves I have are 2 feet and 3 feet long, each are closed at one end, but neither are big enough in diameter to house the flash tubes shown in links here, I am guessing.

 

Hope that clears it up?

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I wonder how big the risk is of exploding flash tubes.

 

I looked around on the web and found several models with bare ring shaped tubes without any domes.

There were also spare domes to protect the tubes mechanical during handling like this one:

https://www.wexphotovideo.com/broncolor-protective-glass-dome-for-siros-flash-head-1565042/

 

I think, without any real experience (mansplaining?) that a flash tube that is not mechanically defect or overloaded has a small likelihood to explode.

 

A quartz flash tube definitely generate harmful UV-B and -C that should be filtered.

I hope the UV-grade perspex I found can do that well enough.

http://www.plasticstockist.com/Sunbed-Grade-Acrylic-Sheet/Clear-Sunbed-Grade-Uv-Perspex-Acrylic-Sheet.aspx

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I wonder how big the risk is of exploding flash tubes. ---

 

There are two basic approaches to failure assessment and handling.

 

1. Assume there never be a failure and be unpleasantly surprised when this event is manifested. The rarer the event the more unpleasant it likely will be experienced.

 

2. Assume there will be a failure, albeit with inherent low risk, and take proactive measures to ensure the bad impact of a failure, if it occurs, is mitigated as far as possible.

 

Looking at the flash designs, the makers obviously have followed Alt.2.

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A quick test with my new Broncolor 1600 Ws studio flash, using a single flash head at 1 m distance with a wide-angle reflector. I used a UV-Nikkor 105mm f/4.5 lens on my D3200 with internal Baader U filter and shot around f/10, ISO 100 with the flash output turned down 2 stops.

 

This flash has an uncoated Xenon 1600Ws tube and a clear quartz protector. It run on mains A/C. I could have used a narrower reflector but was curious to learn what exposure levels could be obtained over a wider scene. The reason for the f/10 setting was that I also compared this capture (in terms of exposure) with that of the 25mm f/2.8 Laowa Ultra-Macro Lens 2.5-5X, which is effective f/9.8 at 2.5X.

 

I also included a patch painted with the Black 2.0 flat black paint (Culturehustle by Stuart Semple).to understand its UV properties. The patch is the smaller of the three circular objects. Also included is some dry Plumeria (assumed to be very UV dark) and my UVEX lab goggles (hopefully they would be UV-dark as well).

 

The test scene is this,

 

T201902103641_broncolor1600WS_UV_UVnikkor105_D3200_BaaderU.jpg

 

and it is obvious the Black 2.0 really holds up well in UV too. Same can be said for the UV protective goggles.

 

Later, I found the Laowa lens needed +2 EV re the UV-Nikkor, which is actually very good, but I don't think its UV response go much below 380 nm. I do need a more appropriate target for that lens, though.

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Cadmium,

Yes it looks like I took your comments way out of context.

You were not discussing actual lights but how to protect yourself from the light.

 

In this case your search terms need to change to "fused silica". That leads to cheaper options like this:

https://www.thorlabs.com/NewGroupPage9.cfm?ObjectGroup_ID=6337

 

But I haven't seen a Bowens mount fused silica tub cover. But I also have not searched that hard.

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A quick test with my new Broncolor 1600 Ws studio flash, using a single flash head at 1 m distance with a wide-angle reflector. I used a UV-Nikkor 105mm f/4.5 lens on my D3200 with internal Baader U filter and shot around f/10, ISO 100 with the flash output turned down 2 stops.

 

This flash has an uncoated Xenon 1600Ws tube and a clear quartz protector.

 

This is really impressive.

Is the flash tube used here the 1600Ws quartz-tube you got from https://xenonflashtubes.com?

 

The clear quartz protector you mention makes me a bit worried. Do you know if it filter any UV-C at all?

I am sure you know how to protect yourself against this, but please be careful.

 

I have gotten the tube of that type, that I intend to use in my Godox AD600BM-project.

I tested the tube's spectrum with my Godox AD200, As I still are waiting for the mounting PCB.

The measurements was done with and without the 2mm sun-bed Perspex, that arrived today.

 

The tube itself emit nasty amounts of UV-C and the Perspex takes care of the worst parts of it.

post-150-0-42867500-1549896220.png

 

post-150-0-59746800-1549896245.png

 

The low level offset of the purple graph, showing the Perspex filtered light is due to crosstalk in the spectrometer, not a leakage of UV-C

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Actually it is an original uncoated xenon tube from Bron. Apparently they rummaged through the most obscure and hidden parts of their inventory to find me one as I waited for months. It is a almost perfect lookalike to the Israeli 1600 Ws tube I got from Xenonflash and thus I would be surprised if they performed significantly different.

 

Always use a long-sleeved dress or similar plus UVEX goggles when I'm playing around with these UV-emitting sources.

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Quick update. As I need to learn more about flashes, I've bought a cheap second hand set to learn with. They are Bowens Gemini GM500 units (a pair of). They were a very good price, and by all accounts are very well built. The flash bulbs they have look to be original ones and to be coated. They do produce some UV, but not a lot. As an example, with one flash only on full power, and placed about 60cm from my hand, if I take a picture of my hand using my ACS UV converted Nikon d810 and Rayfact lens (ISO800, f22), then the exposure looks about right.

 

I asked Xenon flashes the provide me with a quote for some custom quartz flash tubes for them, and the quote came back very cost effective which was a nice surprise, although there is a minimum order quantity of 5. That's fine with me - I'll likely break one given how clumsy I am, so I'd have 2 and 2 spares. Just finalising the details for that now.

 

I've also asked the supplier Ulf mentioned for the sunbed grade UV acrylic for 2 disks of the material that I can mount in the flash reflectors. This will reduce the UVB and C, and provide some degree of protection should the flashes ever fail catastrophically.

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