Jump to content
UltravioletPhotography

Godox AD200 electronic flash (work in progress)


enricosavazzi

Recommended Posts

enricosavazzi

I recently bought a Godox AD200 electronic flash. This is a battery-operated unit somewhat intermediate between a speedlight and a studio strobe. It is rated at 200 Ws, which is at the low end of studio strobes, and in practical use it proves to be about twice as powerful as some of the largest all-in-one speedlights. It is intermediate also in weight, being slightly less than 1 Kg, and differs from earlier models of similar capabilities (e.g. Godox AD360, Quantum models) in that it is a modular but all-in-one unit. In particular, it needs no external battery or external power pack. The head is also modular, with a speedlight-style head, a bare-bulb head and a LED head for continuous illumination so far available.

 

Another peculiarity is that the preferred mode of triggering is with a dedicated 2.4 GHz radio master that fits on the hot shoe of the camera. With Canon, Nikon, Sony, Fuji and, more recently, Olympus/Panasonic Micro 4/3 cameras, TTL operation is achieved. This unit is interesting to me on several accounts. One is TTL operation and relatively high power in an all-in-one, relatively lightweight and relatively cheap unit. Another is the potential of converting one head to UV, while still being able to use the unit for normal photography (with non-modified heads). If it works, it is going to be my first TTL UV-enabled flash.

 

I should be able to publish a detailed review of this model on my web site in a few days, dealing only with use in VIS photography (spoiler alert: it works very well). Eventually, depending on how the UV modification succeeds, I will publish on my site another detailed review. In the mean time, I did a few tests of the unmodified unit in UV photography, which merit some discussion, best done in a post here.

An Initial tests with Baader U filter seemed to show that this flash, with its bare-bulb head and a 12 cm aluminium parabolic reflector, is fully capable of generating UV images. However, the xenon tube clearly shows in VIS the tell-tale yellowish/brownish tinge of UV-cut coatings. I took all pictures with a "full-spectrum" Micro 4/3 camera and CoastalOpt 60 mm Apo lens.

 

post-60-0-68844100-1500663941.jpg

First I took a picture of the AD200 xenon tube used in the bare-bulb head, with Bowens R500 studio flash equipped with non-coated tube and Baader U filter. The Godox tube looks slightly dark, but not dramatically so. Imaged in the same conditions, a UV-cut filter like the Baader UVIR-cut looks almost completely black.

 

post-60-0-61848600-1500663965.jpg

Just for the fun of it, in the above picture I used as UV source the unmodified Godox AD200 with bare-bulb head and 12 cm parabolic reflector, and Baader U filter. Higher contrast, but otherwise the image is not too different. You can clearly see the spiral trigger wire both in front and at the back of the tube, which is transparent enough for this.

 

post-60-0-22242700-1500663987.jpg

Then I switched the Baader U filter with an Asahi Spectra XRR0340 filter, which is an interference coated U-340. Even higher contrast. Note that the protective glass envelope around the tube is completely transparent in all images. Only the tube is coated, and the increase in contrast suggests that it is blocking more of the shortest wavelengths that pass through this filter. However, even with this filter, the tube is nowhere as UV-opaque as a typical UV-cut filter.

 

Does this mean that the Godox AD200 can be used in UV photography without conversion? Not so fast, a really reliable test is done with a spectrometer, rather than by visually comparing images.

 

post-60-0-79811100-1500664527.jpg

To compare very different flash units in a meaningful way, I previously normalized the graphs to display the peak emission level as a value of 1. This is simple, but not really meaningful. In the above graph, instead, I normalized each spectrum to display the same area under the curve between 400 and 700 nm (i.e., the VIS range). In this way, now that the VIS emission is normalized to be the same, we can better visually compare the relative proportion of UV to VIS in each flash. I will give the details of the calculation elsewhere.

 

The four spectra are:

  • blue thin line: Metz 52 AF-1, a typical speedlight that completely filters out UV. Useless for UV photography.
  • green line: Bowens R500 with uncoated tube, at full power. Plenty of UVA.
  • red line: Bowens R500 with uncoated tube, at lowest power. Thanks to the new way of normalizing the graphs, we can immediately see that now the proportion of UV to VIS is much higher than at full power. I will explain elsewhere why, but this is expected.
  • thick violet line: Godox AD200 with unmodified bare bulb, at full power. Not much UV. We can see that the tube coatings are doing their job, and that the unmodified tube is a rather poor choice for UV photography.

In part, the misleading results obtained by visually comparing the images are due to TTL flash metering. The flash was simply pumping out more of its abundant power to compensate for the low amount of UV, quite enough to force it through the transmission "tail" (380-390 nm) of the UV-pass filters.

Link to comment
Fascinating, thanks for sharing Enrico. I've seen a similar effect with an unmodified Canon 600RT with the light being emitted dropping to zero below about 420nm. I've not looked at full studio flash systems for UV yet, so it looks like the Bowens is worth checking out. Also very interesting to see that the relative intensity of the UV changes depending on power. Looking forward to see more of the work :)
Link to comment
enricosavazzi
...

it looks like the Bowens is worth checking out

...

It works for me, but don't forget that I am using the Bowens uncoated tubes, which are an accessory/replacement part at extra cost. The coated tubes that come with out-of-the-factory Bowens strobes do not work for UV photography.

Link to comment
enricosavazzi

The spectrum of a totally unfiltered quartz xenon tube, fired in the AD200:

 

post-60-0-37005800-1501013281.jpg

blue line: full power

red line: 1/8 power

green line: 1/128 power

data normalized as the earlier graph (above in this same thread)

 

We can see that the emission extends into the UVB and UVC, while the "uncoated" Bowens tube is limited to UVA and a small part of UVB. Also, at low power there is a proportionally larger amount of UV vs VIS, and the xenon spectral lines are stronger (especially in the VIS and UVC), relative to the black-body radiation.

 

An unexpected problem is that, just after a dozen or so flashes at full power, the inside of the tube near the cathode (actually about 1/3 of the length of the tube) is coating with a black deposit of evaporated metal. This is most likely the result of overloading the tube (i.e., excessive current density). The tube I am testing is straight, shorter than the original, helical one but approximately the same external diameter. The glass of the original tube is very thin (about 0.5 mm), while the quartz one appears to be thicker, which means the internal cross-sectional area is smaller (which means a higher current density than the original tube).

 

I may need to get a tube with a wider cross-section, to use the full power of the flash.

Link to comment
enricosavazzi

Now we need to tackle the problem of the UVB and UVC radiation, which are dangerous for us and living subjects, but useless since they are not recorded by Bayer sensors (except for the extreme long-end of the UVB, which may or may not have an effect on our sensors, this is still somewhat debatable).

 

post-60-0-25471000-1501050492.jpg

blue line (largely hidden behind the red line): not filtered

red line: filtered with 2 mm thick acrylic specified for use in suntanning beds

 

This filter seems to largely do what I set out to obtain. One possible gripe is that it starts cutting at about 350 nm, but not by a lot. The real cutting starts at about 280 nm and lower. This filter material is cheap, lightweight, available in small to large sizes and varying thickness, easily cut and sanded, and not too difficult to order by mail. It is also mechanically strong enough to act as a containment barrier in case the xenon tube explodes. The terminology used by sellers, however, can be misleading. Some sell this material as "UV grade acrylic", while others use the same expression for acrylic or other plastics mixed with pigments that absorb all solar UV (which is not what you want). Acrylic, as a material, is supposedly already UV-proof and said to last some 20 years when exposed to sunlight, so the reason to add UV-absorbing pigments is probably to reduce UV exposure for humans when used in windows and skylights.

Link to comment
enricosavazzi

Incidentally, while recording and processing the above spectra I noticed that the noise output of my spectroscope is very constant, at least on the short term and at the same temperature and time-length of the measuring window. So I tried to subtract the noise (i.e. a spectrum recorded without flashing) from the recorded data.

 

post-60-0-00101600-1501052623.jpg

The improvement in the parts of the spectrum closest to the zero level are significant, so this simple technique is effective. This is just the same processing that our cameras do by subtracting a dark frame from an image recorded with a long exposure time. Some spectroscopy software can do the same (the dark frame must be manually recorded, since these solid-state spectroscopes have no shutter), but I prefer to process and display the data myself, and learn in the process.

Link to comment
Again, thanks for sharing, very interesting work. Regarding the acrylic I experienced a similar thing - I ordered some PMMA thinking it would be UV transparent, only to find it blocked everything below 400nm. Thankfully I only ordered a small sample just to test it, but you definitely shouldn't trust that the descriptions will accurately describe the properties of the product.
Link to comment
  • 2 weeks later...
enricosavazzi

The next test is with an uncoated replacement flash tube (not quartz, just an ordinary flash tube for photographic use) as similar as possible to the original Godox tube. The closest I found is eBay item 121809484311, apparently rated only to 40 Ws. In spite of the low power, so far it holds.

 

post-60-0-99645600-1501964371.jpg

This is at full power (200 Ws). The proportional amount of UV is similar to the quartz tube filtered with UV-grade acrylic (see above in this thread), except there are no significant amounts of UV below roughly 280 nm. Given that I cannot really record shorter wavelengths than 300-320 nm with my cameras, there is no real reason to prefer the quartz tube to this, much cheaper (USD 8.25) uncoated tube.

 

If durability proves to be a problem because of the low power, a larger uncoated tube (not necessarily of the same shape) would be the next thing to try.

Link to comment
  • 9 months later...

Thanks Enrico!

This is very interesting! My old Olympus FL-36R flash was declared defunct last week by a camera repair man, so I got an excuse to order the Godox AD200. I have also ordered the cheap flash tube from eBay, the same one that you mentioned (even cheaper at the moment). How did you install it? Did you find somewhere a suitable base to connect it to, so that it can be plugged into the AD200 bare lamp head?

Pedro.

Link to comment
  • 2 weeks later...
enricosavazzi

Thanks Enrico!

This is very interesting! My old Olympus FL-36R flash was declared defunct last week by a camera repair man, so I got an excuse to order the Godox AD200. I have also ordered the cheap flash tube from eBay, the same one that you mentioned (even cheaper at the moment). How did you install it? Did you find somewhere a suitable base to connect it to, so that it can be plugged into the AD200 bare lamp head?

Pedro.

Hi Pedro,

The original Godox tube socket has four contacts. Three of them are 4 mm diameter, the fourth is smaller but it is not connected to anything, it is only a "key" to make sure the tube is not inserted incorrectly.

 

For the 4 mm contacts you can use standard 4 mm banana plugs (https://en.wikipedia...anana_connector). Choose a type where you can remove the plastic handle, since there is no space for it. Also choose a type with a screw to tighten the plug to an electrical cable. This will avoid the need to solder the tube contacts.

 

There is a polarity to the contacts of the flash tube, which you should get correctly in order not to shorten the lifespan of the tube. Disconnect the flash head from the AD200 body. Unplug the tube by pulling it straight out (unlock the side knob of the head if necessary) and orient the socket of the AD200 with the contacts facing toward you and the smallest of the four connector holes uppermost - let us call it North. This hole is unused. The other three contacts:

West - this connects with the tube electrode that has a black coating inside the tube.

South - this is the trigger contact, connect it to the center electrode of the tube (the one connected to a metal wire spiraling around the exterior of the tube).

East - the second electrode of the tube, without a blackened coating inside the tube.

 

One potential drawback of this solution is that light from the tube reaches the black plastic inside the AD200 socket. This has not been a problem so far for me. A more elegant solution would be to re-use the white ceramic base of an AD200 tube, but unless you own a broken tube and can do some soldering it is more expensive than three banana plugs.

 

I am preparing for travel for a few days and cannot take a picture of the tube right now, but can do it at my return if the above explanation is not clear.

Link to comment

Wow!

 

***

 

Thank you Enrico for this Godox topic. Very useful!

Link to comment

Hi Enrico, thanks for the testing of this flash unit.

I can get the Godox AD200 kit in Australia.

Where do I get an uncoated flash bulb please ?

Cheers

Col

Link to comment

I got my Godox AD200 more than ten days ago.

At the same time I ordered the uncoated flash bulbs that Enrico referred to.

I ordered a few to have as spares as the power rating is lower that the Godox specified power.

 

The bulbs are still in transit.

 

I found them at eBay:

https://www.ebay.com...872.m2749.l2649

It looks like they ship worldwide.

Link to comment

Thanks Ulf

I'll wait to see how you go at getting them & how thew work first......

Israel is not a country that I would be in a hurry to send money too ?

Cheers

Col

Link to comment

Col,

 

I'll let you know when I have things up and running.

I really like the behaviour and handling of the Godox. Now I'm just waiting for the UV modification parts.

I have an array spectrometer and will show some spectrograms comparing the modified Godox with results from a modified Canon 199A.

 

I do not think there is a problem sending money to a company in Israel.

This company appears to be competent and professional.

My main problem is the last part of the shipping.

 

Currently the Swedish Postal service - customs branch is the difficult one.

They seam highly incompetent after a quick big change of rules causing a lot of kaos.

The last months they have already lost two of the packages I a was expecting.

Link to comment

....waiting for Godox!

Andy, be careful, the Pun Police are gonna come lookin' for ya !!!

At my age I'm waiting for Botox.

Link to comment

Hi,

Assembled and briefly tested: seems to work as expected. I ordered the flash tube recommended by Enrico from eBay and it arrived from Israel to Finland quickly (about 12 days). Bought only one, I should probably order a spare or two. Just from the smell it seems to get very hot. In the case of the flash tube I received both electrodes looked the same, but one was closer to the inner wall next to the outer trigger electrode, so I assumed this to be the anode and connected it to the West contact (as described by Enrico).

Cheers,

Pedro.

Link to comment
  • 3 months later...
  • 3 weeks later...
enricosavazzi

Any thoughts on using Godox 360ii?

Nominally 300 Ws, and taking this specification at face value, about half a stop brighter than the AD200. A quick googling shows an average price close to double that for the AD200. I would pass.

 

Incidentally, a dedicated extension cable is now available to separate the AD200 head from the generator. It makes it easier to place the generator in an orientation where the LCD screen can be seen and the settings can be comfortably changed.

Link to comment
Yes, I find the extension cable very useful, I use it 90% of the time. I noticed that my copy of the AD200 came with a bare lamp that does not seem to be coated. The spectrum reaches almost 300 nm, at least directly in front of the top of the lamp. This seems very different from the lamp Enrico received and measured.The proportion of UVA is la bit smaller than in the XenonFlashTubes.com FT-ST-S40W (this is the same as the eBay seller Enrico recommended) but the total output seems higher. I have also tested the plastic diffuser that came with my ADS-2 reflector and it transmits UVA quite well. There is now a third head available for the AD200, a smaller bare lamp head with modelling light and built-in reflector. Has anyone tried it? Anyway the flash tube in this newest head does not seem easy to replace... http://www.godox.com...Flash_Head.html
Link to comment

Please sign in to comment

You will be able to leave a comment after signing in



Sign In Now
×
×
  • Create New...