Hey all, This isn't really a DIY thing but I was wondering whether anyone thought there could be a chance of one of these mini flashes working as a strobe trigger (if it fits in a housing obviously)?   https://www.godox.com/product-a/iM20-iM22.html   To clarify, I'm not planning on actually doing this, just thinking it could be a potential cheap "emergency backup" option for if my TRT trigger breaks on a trip 😁

This content was not saved, so I edited it and uploaded it again. My native language is not English, so please understand if there are rude English words. I use ulcs tray + inon 45 degree baseball.   It was more stable when the inon base ball was mounted at an angle away from the housing. I used a 6-inch stick arm and used the same maker to make it a little easier to control underwater. I found that using the same maker's ball made the clamp operation smoother. When not in use, I store it so that it does not interfere with the button or strobe placement control.   Also, I leave the tray and base ball on even when I'm not using the tripod. Especially when I'm beach diving, it makes it much easier to clean the O-ring when I leave the camera on the sand.

If you really need faster shutter speeds than 1/250 a trigger like the Nauticam manual trigger is a workaround option.  This is a fully manual trigger and will allow you to set any shutter speed you like and it will work up to something like the 1/400 - 1/500 range and  sync with the shutter with no black band showing.  This is arguably fast enough to deal with sunballs which is a major reason for wanting a faster shutter speed. It also works with any flash not just HSS capable flashes.   HSS becomes increasing impractical as the shutter speed gets faster as the available power drops and even with this option the available power drops as the shutter duration starts to be shorter than the length of the full power strobe pulse.

I assume you are trying to work out if you can use a Tokina 10-17 in an AOI housing with an OM-5 with the OM-D port system that goes with that housing.  If you look at the AOI port chart you will see that the 8mm fisheye uses the 22mm extension with the DLP-01/02.  If you look at the Nauticam charts you will the 8mm fisheye uses a 17mm extension with the 140mm port and to use the 10-17mm on a metabones speed booster you need the 34.7mm adapter and a 10mm extension to use with the same dome.   Based on this for AOI you need (34.7 + 10 = 44.7) - 17mm = 27.7mm more extension than the 8mm fisheye to use the tokina lens with AOI.  SO a total of 22 + 27.7 = 49.7mm.  OM-D ports only have two extensions 22 and 52mm and the Pen ports only offer 24 and 34mm extensions.  The 52mm might work but it could vignette.   If you could go to a store that has the housing and extensions in stock you could try them out - you can tell if vignettes on land in the shop if you put it all together.  A safer course might be to go with an Isotta or Nauticam housing it's more expensive but they have a full range of extensions to work with.  The 10-17mm will work perfectly well in the Nauticam 4.33" & 140mm domes, the Zen 100mm dome and the Isotta 4.5"dome.     I use the Canon 8-15 on my OM-1 with a 140mm dome on Nauticam.  It's quite expensive to adapt these lenses on that system but the Isotta will be significantly cheaper.  From everything I hear the Metabones speed-booster/smart adapter is the better option for adapting canon mount lenses to Olympus.  The smart adapter is for the Canon 8-15 while the speed booster gives a 7-11mm fisheye with a Tokina 10-17.  

I have found in RC the camera mounted only flash can be slow and lag strobes I also have been using set to fill in per older manuals  for older cameras than my O-M1 not 1/64 that I do use in non RC TTL or manual. I will note that O-M1 manual indicates in RC mode it can take up to 4 seconds to be ready to fire, which is glacial slow.