Is the Godox AD200 TTL Pocket Flash Kit UV Convertable

[Zlieb43]

Just as the title says, is the Godox AD200 capable of being converted to a UV only emitting flash, aka, UV emitting visible spectrum absorbing flash?

[ulf]

Yes it is.

At least when using the flash bulb-module with a suitable non standard xenon flash tube and a standard reflector.

 

I have no idea if the flash tube in the speedlight module is coated.

Have not wanted to take that module appart, as it has been easier to experiment and replace the bulb flash-tube.

In my experiments the goal was never to create an UV-only flash as I'm not into flash-based fluorescence photography.

 

You have to use and a suitable filter stack to filter out VIS and possibly some NIR.

The round standard reflector has a diameter of 120mm

The filter stack is likely to be very expensive for that diameter.

[Cadmium]

I think it is like this one?

http://www.ultravioletphotography.com/content/index.php/topic/2539-neewer-ad200-flash-for-uv-imaging/page__p__18967__hl__+godox%20+ad200__fromsearch__1#entry18967

[ulf]

I think it is like this one?

http://www.ultraviol...h__1#entry18967

 

That link show the original Godox bulb. It do not transmit much UV and the filter mount inside the reflector blocks much light emitted from the arc.

 

Here are some pictures from my experiments with different flash tubes on my AD200: http://www.ultraviol...dpost__p__25662

[Zlieb43]

Ok so would I would have to replace the bulb with one of the ones in that link and then get the pieces of glass to filter it properly right? Cadmium, is that the same ones that you make?

[Cadmium]

I don't know. I don't have one of those. That link was from Boon. If you go to the first link in that topic, you can message Boon, he knows quite a bit about that flash, and the bulbs.

As far as I know, I have never made anything for that flash.

[Alaun]

This might be the first reference here:

http://www.ultravioletphotography.com/content/index.php/topic/2343-godox-ad200-electronic-flash-work-in-progress/page__hl__ad200

 

 

 

[ulf]

I took a closer look at the Godox Speedlite H200 Head.

 

It is easy to take apart by removing two screws.

When one half of the cover is removed one can see the protective glass between the outer fresnel lens and the reflector.

 

The Xenon tube is tiny and I am rather sure that it must be a quartz tube to survive the 200Ws the flash is rated to be.

 

I know from previous measurements that with all parts in place there is no output below 400nm.

Let's see how removing parts will change this.

[ulf]

The spectral output from the flash's light, bounced off a PTFE sheet, measured with my spectrometer:

 

 

Red, Bare flash tube in its original reflector:

I think that the reason for the UV-drop towards shorter wavelengths, beginning at 370nm is due to lower reflectivity of the reflector mirror there.

The light below 335nm comes directly from the arc in the tube. The light above 335nm is a combination of reflected and direct light.

 

Green: Protective glass sheet added.

The glass sheet cuts away almost all UV-C, good for safety, but it also reduces the already rather low UV-A and UV-B.

 

Blue: Glass sheet + Fresnel-lens added

The Fresnel-lens is cutting almost all UV due to the material properties. Polycarbonate?

[ulf]

I also compared the output from the two original flash modules, Speedlite and Bare bulb, to the output from Canon 199A, without the front fresnel lens:

 

Brown: Canon 199A. Orange: Godox Bare Bulb with Godox standard reflector. Blue: Godox Speedlite H200

 

These graphs are normalised to show the same average intensity above 450nm and are only for comparing the spectral content, not the actual intensity.

The Canon flash is slow and less powerful compared to the Godox AD200.

 

It's quite clear that the original Godox Bare-Bulb emit some UV, but mainly closer to 400nm, where traditional UV-pass filters like Baader U have very little transmission.

[dabateman]

I also compared the output from the two original flash modules, Speedlite and Bare bulb, to the output from Canon 199A, without the front fresnel lens:

 

Brown: Canon 199A. Orange: Godox Bare Bulb with Godox standard reflector. Blue: Godox Speedlite H200

 

These graphs are normalised to show the same average intensity above 450nm and are only for comparing the spectral content, not the actual intensity.

The Canon flash is slow and less powerful compared to the Godox AD200.

 

It's quite clear that the original Godox Bare-Bulb emit some UV, but mainly closer to 400nm, where traditional UV-pass filters like Baader U have very little transmission.

 

Am I reading your graph wrong? The Canon 199A, brown looks to have the most uv output of what you tested.

[ulf]

Am I reading your graph wrong? The Canon 199A, brown looks to have the most uv output of what you tested.

Yes you are!

The sentence below the graph can be useful to read. :)

 

The Canon 199A has the best spectral content, but there is no valid absolute intensity information left in the graph as they are normalised against each other.

The intensities from the beginning between the three could have been very different.

The graph for Canon 199A is from an old measurement that I imported, just to show for comparison of the spectra, not the intensities.

---

A point light source will follow the square rule of intensity decay.

A light source with a more focussed light pattern from a reflector like most flashes will not do that.

The results will depend on the distance between flash and reflective PTFE measurement surface as different flashes have more or less focussed radiation patterns.

---

The graph below might make things more clear if I can explain them in an understandable way. :(

 

The graphs below are the measurement result before normalisation.

Here all three graphs are from the flash in the exact same position, relative to the PTFE-sheet.

The distance between the front of the flash and the PTFE-sheet was ca 25cm.

 

The filter glass and then the fresnel lens was added by placing them resting against the flash's reflector, without moving the flash.

The fresnel lens is not as wide as the flash and do not fully cover the reflector.

---

My conclusions:

 

The difference between the green and the red graph is indicating the losses caused by the filter glass that appeared to be coated.

 

The blue graph (filter glass plus fresnel lens) show two phenomenon:

 

1. The fresnel lens width cause some leakage of shorter UV, seen as the bump between 340nm and 410nm.

That made me replace that measurement, in the first graph in post #9 earlier in this topic, with one made with the flash head completely assembled.

That measurement was done with the flash in a different position showing a different intensity. Hence the need for normalisation.

 

2. The fresnel lens make the light more focussed, increasing the intensity at the PTFE sheet, but also cutting of the UV

[dabateman]

Thanks,

As soon as you said Normalized and imported from old data, it makes perfect sense to me. You can't really do that unless you have a common reference to match them with. Thus the 199A line doesn't mean anything. Even the shape of the curve will be different based on changes to your spectrometer over time.

[ulf]

Thanks,

As soon as you said Normalized and imported from old data, it makes perfect sense to me. You can't really do that unless you have a common reference to match them with. Thus the 199A line doesn't mean anything. Even the shape of the curve will be different based on changes to your spectrometer over time.

 

I do not fully agree with you that the 199A measurement is nonsense.

The measurement setup is reasonably stable.

The blue lines in the first and last diagram lined up rather well, except at the bump between 340nm and 410nm after normalisation.

Those measurements are made a several months apart.

 

What you cannot see is the absolute power, but the spectral content is still valid.

The last graph show the intensity change.

 

I will try to find a setup that gives meaningful comparisons for intensity between different types of flashes and flash heads.