Mobile phones are getting seriously good for cave photography now, but after quite a bit of digging about online it seems there is no way to fire remote flashes (ideally radio triggered ones) with a phone. 

There does look like there have been attempts at some bluetooth modules (like the Godox A1) but none seem get fully developed and/or are still available to purchase. Tric flash http://www.tricflash.com/ looks like the only one openly in development, but it's still only in pre-order and only for iPhones  :ras: . And then there's some horrifically expensive LED based ones (https://innovatronixshop.com/products/innovatronixcpflash) that i'm certainly not going to touch.

Has anyone else had any luck finding a way?

PS yes i know you can do this by firing the flash manually, using a slow shutter in manual mode (if you can on your phone), whilst sat in the pitch dark, but i don't want to 

I use firefly modules that activate when the main flash operates.

The Tric flash seems like the most practical solution given the phone itself can't be modified - if they can actually get it out to production, and open it up to more platforms other than Apple. it may be they have to sell enough units to rich folks first to open up development for the proles. The only thing is - if you're taking a bunch of flash guns in anyway, is a real camera that much of an impediment, given it already works and does astounding quality? I know it's heavier than a phone, but it's a lot more robust too for underground?

Godox X2t can connect via bluetooth to a phone (most reliable on iPhones by the looks of it), and trigger any of their flashes.

The argument I'll come back to is why, once you're at the point of carrying 2/3 flashes, having an actual camera isn't that much of a difference.

In a 6L daren drum I can fit 5x flashes, my Fuji x70 and a trigger (plus some spare batteries). If going small, I could probably squeeze 3 flashes plus camera plus trigger in a small daren drum. How much space are you really saving by using a phone instead of a camera.

JoshW, thanks for the Godox X2t idea, i'd not spotted that. Indeed that comes close, just a shame it's not better with Android (it doesn't work with mine, i've just tried their app), and it relies on all the flashes being proprietary, although not too much of an issue as Godox gear is good and not too expensive.

Josh and Phil, sure an SLR is not much of an impediment, especially if you're taking loads of flashes. However turning around your example, I'm very used to taking my phone underground at the moment (for a mixture of surveying, snapping and music) and a flash or two extra would not be much of an impediment and could drastically improve my snaps.

My phone is not necessarily trying to replace my SLR, but is has already replaced my compact camera. A good smart phone (say ~?500) will now get you better quality images than most good compact cameras, will be IP68 with a range of cases to further improve robustness, and have a million other features that your compact camera could only dream of. Many cavers use an external flash with their compact cameras, so it makes sense to get a solution for phone cameras too...

Rob said:

I'm very used to taking my phone underground at the moment (for a mixture of surveying, snapping and music)

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You take music underground?!? 

Surely one of the best things about being underground is escaping the noise of everyday life?

Something like a phototransistor taped over the phone's flash (plus a few other bits - battery, resistor, opto-isolator) comes to mind

PeteHall said:

Rob said:

I'm very used to taking my phone underground at the moment (for a mixture of surveying, snapping and music)

Click to expand...

You take music underground?!? 

Surely one of the best things about being underground is escaping the noise of everyday life?

Click to expand...

We usually always have music playing at our digs.

Mark

Nowt like a bit of drum and bass to spur on whatever member of your club you've managed to trick into going digging

Never was a big Peter Gabriel fan, but the video seems relevant for digging music

https://www.youtube.com/watch?v=X0C3DHp36zc

Given the cost of waterproof compact cameras (e.g. Olympus Tough series) is comparable to that of a good phone, I expect phones to replace them over time.
+1 for digging music, though be very careful who you allow to choose the music - I had to endure "Baby Shark" the last session before lockdown, but then again the offending phone is still down there (Luke is not).

Trigger: I think some selfie sticks use the audio jack to trigger, I have no idea what the phone interprets as "take a photo", but I'd assume it's continuity between GND and either left or right. Or both. Easy enough to find out. At that point you can use the same switch to trigger the flash. Would require some basic electronic skills, but nothing too sophisticated I should think.

AlexR said:

Trigger: I think some selfie sticks use the audio jack to trigger, I have no idea what the phone interprets as "take a photo", but I'd assume it's continuity between GND and either left or right. Or both. Easy enough to find out. At that point you can use the same switch to trigger the flash. Would require some basic electronic skills, but nothing too sophisticated I should think.

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In iPhone camera apps pressing the volume button takes a photo, and this is the same if you're using the cabled headphones with inline audio control, so theoretically a long headphone cable should do the job?

If you really want to get fancy, if you've got an apple watch you can use that as a trigger for an iPhone that works over bluetooth. Assume android has an equivalent.

Here's how to use the headphone socket to take photos - you could use the switch to trigger the flash as well (e.g. Get a 2 pole switch and use the other pole for the flash trigger) - https://www.youtube.com/watch?v=DTFMrZsjBOo

I like the idea of the switch, but on my phone anyway between pressing the camera shot and the picture actually taking there's a short delay. I worry that the pic would take just slightly after the flash had fired?

Cantclimbtom said:

I like the idea of the switch, but on my phone anyway between pressing the camera shot and the picture actually taking there's a short delay. I worry that the pic would take just slightly after the flash had fired?

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Usually that's because it focuses and adjusts for exposure after you've pressed the shutter. In iOS if you hold down and press on a section of the screen it locks AF and AE on where you've pressed and the time between pressing the shutter and the photo being taken is much shorter..

outside of the iOS stock app I've no idea if that's the case. It's an electronic shutter (not mechanical) so there's no reason for there to be a delay if you can set the exposure/focus before.

Cantclimbtom said:

I like the idea of the switch, but on my phone anyway between pressing the camera shot and the picture actually taking there's a short delay. I worry that the pic would take just slightly after the flash had fired?

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I agree, even with the best intentions, putting adjustable delays into the trigger and using various phone settings, i think this is going to be a loosing battle. Especially if using short shutter speeds. Probably why it's not been done...

Rob said:

Cantclimbtom said:

I like the idea of the switch, but on my phone anyway between pressing the camera shot and the picture actually taking there's a short delay. I worry that the pic would take just slightly after the flash had fired?

Click to expand...

I agree, even with the best intentions, putting adjustable delays into the trigger and using various phone settings, i think this is going to be a loosing battle. Especially if using short shutter speeds. Probably why it's not been done...

Click to expand...

I think the godox ones have a max flash sync of 1/60th, which really isn't the end of the world for underground stuff, unless you're photographing near an entrance and really trying to overcome the sun.