First, an introduction. I take pictures underwater as a hobby, and build underwater propulsion systems as a business (www.jetboots.com).

I don't post here much, but lurk frequently and have learned a lot. I've just gotten a digital rebel, and after exploring my housing options came up with what might be a neat idea.

Here are the basics:
1) Take up to four(!) 550EX speedlites and house them in a mostly clear polycarbonate or acrylic housings (easy)
2) Take a ST-E2 wireless transmitter and build a clear housing for it with bulkhead connector (easy)
3) Wire the ST-E2 to any housing and mount it on top of the housing with a reflector to send most of the IR pulse in two cones directed sideways (fairly easy)

Now you have a wireless strobe system with E-TTL. The only real problems I can see are:

A) Getting the ST-E2 to talk to the camera well with all the connectors the signal must pass through (try and see)

Getting enough IR transmission underwater to make the system work. My first guess is the IR transmission will work fine in reasonable vis - the IR LEDs work around 900 nm, which is only a couple of hundred nm outside the human visual range, so the transmission probably won't be down too much. The stated range of the wireless system on land is about 30' - since the light falloff is 1/r^2, and an average strobe to camera distance is about 2', we would need an attenuation of around 225x between the camera and strobe to make the strobe miss the signal - seems unreasonable if the optical vis is good enough to be taking pictures. I'm looking for some references of optical attenuation in seawater to verify this.

Can you guys think of any other potential show stoppers?

B&H has the two speedlites and the transmitter for $800, and I'm guessing that I could build the three housings for about $1000, for a total cost of $1800 for a two strobe system.

Would the canon users out there be interested in this if it works? What if it only works right 95% of the time?

What kind of strobe mounting point would you prefer?

Ikelite or Nikonos bulkheads?

What max depth rating is acceptable? (remember, the deeper the bulkier)

Ben Mazin
President, MST, Inc.
ben@jetboots.com

I thought about this idea a long time ago using the original Minolta wireless system.
I am told by Minolta not to waste my money as it will not work efficiently if at all through PC even in distilled water without using a fibre optic link.

I'd love this to be proven wrong all the same...

I have also thought about this approach.

The canon EOS system requires 6 pins for ETTL. so the Ike and Nikonos connectors cannot be used. The europeans are using a 6pin connector called the S6 for the EOS strobe housings.

an interesting feasability test could be done by placing the camera and ST-E2 on one side
of a large aquarium and the slave stobes on the opposite side. a Nice 125 gal should work.

The most important feature, IMHO, should be access to all the controls on the ST-E2.
full flash ratio would be pretty cool!

rich

Great minds thinking alike - I was planning on doing the aquarium test today. I'll have to use some black fabric to mask off the room, since the IR bounces well and could easily go around the aquarium. Stay tuned.

Anyone know a source for the six pin bulkheads?

Using a fiber optic link is NOT out of the question... Fiber optic kits are available from Sea and Sea and Inon.

Cheers
James

It's cheaper from an electronic supplier by the drum!

True, there are fiber optics specifically designed to carry IR like Ocean Optics VIS-NIR fiber, which has an attenuation of somethinge like .002 dB/m (!) at the appropriate wavelengths (my day job is a research astronomer at Caltech, so I've a bit of experience with this sort of thing)

Ocean Optics Fiber

This could almost certainly be made to work - a good fallback plan if the aquarium test comes up negative.

Hey,

I like the idea of the fiber optic but I don't think the transmiter or the IR receiver are necessary.
The transmitter (I think) is is only an signal-to-light converter and its only purpose is to attach on the hot shue on the camera and sent the ETTL signal through infrared.
... You can do this by simply having a level adapter from the hot shue and a coupple of op amps to boost the signal up for the infrared LEDs.
On the other side, same stuff only reversed, get a phototransistor and have an ampliffier to get the infrared signal transformed to signals.
I don't know what is the rating on the hot shue (5V TTL - as in transistor transistor logic not through the lens -, 3v CMOS, 12 V serial ????) but it would be easy to build such an adapter.
(I am writing firmware in my day job and play a lot with hardware).

I think a better idea is to skip the visual signals. We all know that IR is (almost) dead and everything is levitating toward radio.

Why not put a pair of radio transceivers (.... by the way, is is a two wais communication or is just camera -> flash) or a transmitter-receiver and do it like this.
I don't have any experience with radio vawes underwater but I do have a coupple of radio transmitters/receivers that I bough very cheap and are about 1cm/2cm/.3cm.
I tried them out and thye work in analogue mode or in digital mode (as in you can send a voltage level or a TTL signal).

If you are intrested I can dig in my reccords to see where I bought those and let you know and I can help with the wiering (it is very easy).

Let me know if you need help
Vlad

If you're going to go to all of that trouble housing the 550EX speedlites, can't you just go all the way and get some of those S-6 sockets and do a traditional sync cord connection?

Well...let's wait and see the results of the "fish tank" test. :-)

Cheers
James

Canon experts correct me if I am wrong, but I think that E-TTL only supports one wired strobe - to get multiple strobes you need to go wireless - the wired distributor based system only works on the old style stobes (A-TTL?).

I found this very nice canon EOS strobe faq, check it out:

EOS Strobe FAQ

One other thing that might be very neat about getting this scheme working would be FP flash mode, which would allow fill flash with very high shutter speeds to freeze sunrays/sunballs.

It works.

This was taken with a digital rebel, ST-E2 transmitter, 550EX strobe, 18-55mm EFS lens, f/4, 1/160 sec.

The camera was placed at one end of a 3' long aquarium with rather crummy water quality and some algae on the walls. The aquarium is made of 3/8" glass. A bellows was constructed so all the light from the transmitter needed to pass through the aquarium to get to the strobe, which was held at the other end of the tank and pointed back towards the camera. If the strobe fired, we expect a bright light in the camera field, which we see. If E-TTL is working, it shouldn't be all that blown out, as seen.

Apparently, Canon uses some kind of small flash bulb with an IR filter in front to send the info, and you can see a distinctive red flash as the strobes communicate - the wavelength is probably lower than I expected, hence the transmission easier. I tried multiple shots, and it worked perfectly every time.

Since this trial was sucessful, I am going to build some housings for the strobes and a little more complicated one for the ST-E2 to allow access to the strobe balance and FP modes. Should be fun!

Wow, that's awesome news! Thanks for the info.

Boy, it sure looks like you scared the stuffing out of your perculas though! :-)

Cheers
James

There is also a wireless transmitter for Nikon cameras / flashes?
(I can't find something like this in Ritz and Adorama)

A quick update - I've pretty much abandoned this plan since Aquatica seems to have gotten things working with their ICU board and this will allow me to use more powerful underwater strobes than the 550 EX. No fast pulse mode, but I'll live.

That is an EXCELLENT FAQ!