Lightning Capture Device - Cheap - Simple & it works

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Niglyn

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Hi, There have been some discussions (in other groups) of how to photograph lightning and some of the (over-priced) gadgets that are available to assist.

Well, after my other successful photography related electronic gadgets, I thought I would build & share my lightning capture device.

It will follow my normal format of a series of documents listing parts required, how to build it, how to load the firmware etc, as well as the most useful instructions.
Whilst the Lightning Capture is all up, tested* and working, the documentation will follow along as it is written.

All documentation will be posted on Github



The first draft of the instructions are below.
Please give any feedback, ideas or comments to help me improve the device, or indeed any other project ideas.
GitHub repository where all documentation & code can be found. billbill100 (github.com)

V1.0 18/07/2024

Lightning Capture Operating Instructions


Buttons

Blue button. Each time this button is pressed, the marker will move to the next parameter. (Currently only two parameters)

Blue knob. Turning the knob will change the parameter.

Green. Starts the Lightning Capture to watch for lightning.

Blue button. Ends Lightning Capture & returns to parameter screen.


LEDs

Red LED. Power.

Yellow LED. Half Press Shutter – watching for Lightning.

Green LED. Full Press Shutter – taking a photo.


Light Sensor

Blue/White screw. Adjusts sensitivity of Light Sensor.

Green LED. Light Seen


On-Screen Parameters

Pre.

Sets how long the camera will wait with shutter ‘half-press’ watching for lightning.

Pst (post)
How long the shutter will stay open for, when triggered by lightning.

Battery
Alternates between voltage and percentage. Only show whilst in parameter menu

Note:-
The two parameters above are normally set to INF (infinite) and Cam (camera settings). However, they can be changed from 1/1000s to 480 seconds.



Basic operation
The Light Sensor must be adjusted using a small screwdriver, so that in ambient light, the green led on the board just turns off. Note, there is a secondary green power light on the board, which is always on.

The Lightning Capture is connected to the camera using a suitable shutter release cable.

The camera must be in manual mode, including focus & iso.
Focus the camera either at infinity or at a suitable distance, if also including foreground.

Set the camera iso, shutter speed and aperture as appropriate. This will involve a little trial and error and setting will depend on ambient light and if you are being creative with light-painting or fill flash for the foreground.

Press the Green start button & the camera will act the same way as half-pressing the shutter button and the Yellow LED will illuminate (ensure LEDs will not fog the photo)

When lightning is seen, the shutter will be fully pressed and the Green LED illuminate.

The camera will now take a photo, for the duration it has been set to.

The Lightning Capture box will immediately release the shutter and half-press again, watching for the next lightning strike.

Note:- The camera settings take priority. So, if the camera is taking a 30 second exposure, until this has expired, the camera will ignore the request from the Lightning Detector to half-press the shutter.

Fun & Games
The ‘pre’ parameter specifies how long the Lightning Capture will wait for lightning. The default is infinity, however this can be set between infinity, 480 seconds to 1/1000s. At the end of this time, a photo will be taken, even if lightning is not seen. This can be used as an intervalometer, or if the camera has pre-capture & is set to do so, one can save the pre-capture photographs.

The ’Pst’ or Post parameter sets how long the shutter stays open for. Normally this is set on the camera, however if the camera is set to Bulb mode, then the Lightning Capture can control the exposure time.

The camera of course, need not be set to Manual or Bulb mode. For example, it could be set to continuous shooting at 1/60s. By setting the Pst to 5s, one would get a burst of 1/60s stills for 5 seconds.

This could be used to take a series of shorter photographs once lightning is seen, for manual blending & editing.

For cameras with pre-capture, this can be used to capture the pre and post lightning (removing latency issue) by setting the camera up for pre-capture. When lightning is seen, the pre-captured images will be saved and a series of post-images will be taken depending on the ‘Pst’ setting.

Note:- The Lightning Capture has a minimum shutter press length of 1/1000s. It is unlikely a faster shutter speed would be required, however if the camera is set to something like 1/8000s, there may be multiple 1/8000s images taken.



General Notes
Shutter latency is the time from when the shutter is pressed to the time the camera has lifted the mirror & opened the shutter. This can be many milliseconds. The Lightning capture also has latency between lightning being seen and it operating the camera. This cannot be helped. All electronics will have some latency.

For this reason, the Lightning Capture has been coded to minimise latency, with priority given to looking for lightning and operating the shutter, before updating the display. This is also why the camera sits in ‘half-press’ mode waiting for lightning.

Caveat.
The Lightning Capture has been built & tested and all works well. The one thing that has not been tested is photographing actual lightning! It is just a waiting game until a suitable storm comes along.
 

koraks

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All documentation will be posted on Github

Is it correct that this is not yet the case? I was looking for it, mostly out of curiosity what kind of sensor you're using, but the project doesn't seem to be online yet.
The reason I was looking at this was to get a feeling for the latency, which you also address towards the end of your post.

Btw, in case the latency turns out to be an issue, you could always use it in the opposite direction: open shutter in bulb, and then close it as soon as flash is detected. Then open again. That's how I do it manually. It's nicer of course if the trigger actually happens on the flash, of course. I never really looked into how long a lightning flash lasts and whether it would be feasible to trigger within that timeframe. I mostly use SLR cameras and I always imagined they'd be too slow, with the mirror movement and all that. But I haven't looked into it!

I did do a few lightning captures the other day, but the view from my window wasn't particularly interesting and the hits were not in very opportune areas/places. I did this the brute force way by just doing sequential bulb exposures. Digital film is free, eh...
 
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Niglyn

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Joined
Feb 26, 2022
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423
Location
Surrey, UK
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Is it correct that this is not yet the case? I was looking for it, mostly out of curiosity what kind of sensor you're using, but the project doesn't seem to be online yet.
The reason I was looking at this was to get a feeling for the latency, which you also address towards the end of your post.

Btw, in case the latency turns out to be an issue, you could always use it in the opposite direction: open shutter in bulb, and then close it as soon as flash is detected. Then open again. That's how I do it manually. It's nicer of course if the trigger actually happens on the flash, of course. I never really looked into how long a lightning flash lasts and whether it would be feasible to trigger within that timeframe. I mostly use SLR cameras and I always imagined they'd be too slow, with the mirror movement and all that. But I haven't looked into it!

I did do a few lightning captures the other day, but the view from my window wasn't particularly interesting and the hits were not in very opportune areas/places. I did this the brute force way by just doing sequential bulb exposures. Digital film is free, eh...

Hi, thanks for the swift reply :surprised:)

I have started the Photrio thread first, as I need the link, which in turn is added to the documents.
I found with my splash timer that live-view on my dslr was far slower than using the optical finder and the time needed to raise the mirror.

For water-splash this is fine as there is plenty of time between drip release and waiting for the splash. However for faster things like shooting water-balloons & the like, one has to turn the lights off first, open the camera manually, with the timer firing the flash at the required time.

For simplicity, I'm using an Arduino light sensor module. It has a photo-resister & an IC to give a nice clean output. Alternate would be to an LDR to feed a transistor but now we are into mucking about with vero-board or making a pcb.

Hopefully it will be fast enough. Whilst lightning is of course travelling at the speed of light, it does hang about for a while.
 

koraks

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It has a photo-resister & an IC to give a nice clean output. Alternate would be to an LDR to feed a transistor but now we are into mucking about with vero-board or making a pcb.
Are you sure the module uses a photo-resistor, not a photo-transistor? That's what most do, AFAIK. Which is good, because those are a couple of orders of magnitude faster than an LDR. Not sure how much latency there is between the shutter button press and actual exposure start in a typical, modern SLR. I think it's something like 10-30ms, but I don't know...

The good news is that according to Google, a typical lightning flash has a duration of several hundred milliseconds (!), which in reality is a burst of brief flashes of a few us each. This means that you should be plenty fast enough regardless of what sensor type you use. I always imagined a lightning flash to be much shorter, but appear much longer due to persistence of vision.

it does hang about for a while.

Yeah, sort of, as it turns out. It's apparently a stroboscope effect rather than a single flash. Which helps our case!
 
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