optical lightning detector

Buy one of the consumer digital cameras that has a SDK. Set it to record video for 20-30 seconds at a time, and wait for a input from your flash detector via serial or USB. If there was a flash, save or download the video. If not, start recording again.

Steve 

Cydrome Leader wrote:

> Jon Elson <jmelson@wustl.edu> wrote:
>> Cydrome Leader wrote:
>> 
>>> I want to concoct a trigger to fire my camera when there's lightning in
>>> the area of where the camera is pointed. I do not want one of the RF
>>> burst detectors, as I don't care about lightning that's not in front of
>>> the camera itself. I'm thinking about some sort of photodiode mounted in
>>> a housing peeping through the viewfinder for actual flash detection.
>> Digital, camera?  Most of them have massive delay between pushing
>> the button and actually taking the picture.  There often is a sports
>> mode that reduces the delay.  But, I suspect this will be a problem
>> with most digital cameras, they will take a picture of black sky, a
>> large fraction of a second AFTER the lightning.
> 
> the camera is fast, so lag won't be a problem, but figuring out how to
> adjust everything will be, as I can't summon a lightning storm at any
> time.

The DSLR shutter lag really is significant. We're talking on the order of 
100ms, and this is assuming you have a mirror lock capable camera and are 
not using autofocus.[Prefocus and leave the camera in manual.] 
> http://www.imaging-resource.com/PRODS/canon-5d-mkiii/canon-5d-mkiiiA6.HTM

The lightning flash lasts about 100ms
> http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lightning2.html#c2

The way these shots are done at night is you just leave the shutter open (B) 
and stop it down a bit. That gives you a long exposure time. When the flash 
occurs, close the shutter. 

In the daytime, they use a neutral density filter. Same basic technique.

To do what you want to do will require an external camera shutter. Some can 
fire in under 20ms.

Uman has a few books on lightning. Well worth the money.

 

On Tuesday, June 24, 2014 6:46:25 PM UTC-4, the rain in spain. wrote:
> Buy one of the consumer digital cameras that has a SDK. Set it to record video for 20-30 seconds at a time, and wait for a input from your flash detector via serial or USB. If there was a flash, save or download the video. If not, start recording again.
> 
> 
> 
> Steve

Yes, that's clever. An even simpler way is to not use a detector. Do time lapse 
photography every night, each 20 s. long, and if a thunderstorm happens, review 
your photos. If not, erase the photos. (total chip erase.)

simple. easy.

On Tue, 24 Jun 2014 17:51:17 +0000 (UTC), Cydrome Leader
<presence@MUNGEpanix.com> wrote:

>I want to concoct a trigger to fire my camera when there's lightning in 
>the area of where the camera is pointed. I do not want one of the RF burst 
>detectors, as I don't care about lightning that's not in front of the 
>camera itself. I'm thinking about some sort of photodiode mounted in a 
>housing peeping through the viewfinder for actual flash detection.

With a very fast camera, that might even work for night time
photography, however, for day time photography, the change in total
light input for a wide angle detector is not that great to make a
reliable detection.

Have you tried a video camera (preferably setting it a bit
underexposed) and in post processing skip the "uninteresting" frames ?
Doing some change detection between frames should help in elimination.

Cydrome Leader <presence@MUNGEpanix.com> wrote:
> I want to concoct a trigger to fire my camera when there's lightning in 
> the area of where the camera is pointed. I do not want one of the RF burst 
> detectors, as I don't care about lightning that's not in front of the 
> camera itself. I'm thinking about some sort of photodiode mounted in a 
> housing peeping through the viewfinder for actual flash detection.
> 
> Past that, I'm not too sure of what's next.
> 
> Has anbody build something like that before? I'd like to somehow be able 
> to tune the detector's sensitivity to the flash or light as well as the 
> risetime of whatever it's detecting.
> 
> I've not yet tested if photographic slave modules actually pick up on 
> ligtning. Has anybody ever tested this?

I don't know how he does it here, but he seems to mostly take HDR
photographs.

http://davedicello.com/2014/06/pittsburgh-lightning-2/

Greg

Cydrome Leader <presence@MUNGEpanix.com> writes:

> I want to concoct a trigger to fire my camera when there's lightning in 
> the area of where the camera is pointed. I do not want one of the RF burst 
> detectors, as I don't care about lightning that's not in front of the 
> camera itself. I'm thinking about some sort of photodiode mounted in a 
> housing peeping through the viewfinder for actual flash detection.

I'm boring and offtopic, but check out what can be done with
a cheap Canon camera and CHDK (Canon Hack Development Kit):

http://chdk.wikia.com/wiki/Samples:_Lightning_photography

With digital cameras you can do continuous exposures and pick the
frames that contain a strike. Or the video+motion detector mode
can detect the pre-strike and start the exposure in time.

Previously I got some very nice strike pictures on slide film by doing
long exposure after an another and closing the shutter only after a
strike or some experimental time when the frame was already exposed
by the background.

Shutter delay of cameras is usually too slow to catch a strike
even from pre-strike trigger when using the external camera
trigger connection. 

-- mikko

Cydrome Leader wrote:


> the camera is fast, so lag won't be a problem, but figuring out how to
> adjust everything will be, as I can't summon a lightning storm at any
> time.
Well, I think using a camera flash (especially cellphone camera) indoors
would be a good lightning simulator.  I'm pretty sure you could use a small
photocell as a sensor, reverse biased to some modest voltage, and
capacitively coupled to a current to voltage (transimpedance) amp.
Then, high-pass filter the output of the amp.  Final calibration
of the trigger threshold would need a storm, but you can probably get
it close with a flash.

Jon

miso <miso@sushi.com> wrote:
> Cydrome Leader wrote:
> 
>> Jon Elson <jmelson@wustl.edu> wrote:
>>> Cydrome Leader wrote:
>>> 
>>>> I want to concoct a trigger to fire my camera when there's lightning in
>>>> the area of where the camera is pointed. I do not want one of the RF
>>>> burst detectors, as I don't care about lightning that's not in front of
>>>> the camera itself. I'm thinking about some sort of photodiode mounted in
>>>> a housing peeping through the viewfinder for actual flash detection.
>>> Digital, camera?  Most of them have massive delay between pushing
>>> the button and actually taking the picture.  There often is a sports
>>> mode that reduces the delay.  But, I suspect this will be a problem
>>> with most digital cameras, they will take a picture of black sky, a
>>> large fraction of a second AFTER the lightning.
>> 
>> the camera is fast, so lag won't be a problem, but figuring out how to
>> adjust everything will be, as I can't summon a lightning storm at any
>> time.
> 
> The DSLR shutter lag really is significant. We're talking on the order of 
> 100ms, and this is assuming you have a mirror lock capable camera and are 
> not using autofocus.[Prefocus and leave the camera in manual.] 
>> http://www.imaging-resource.com/PRODS/canon-5d-mkiii/canon-5d-mkiiiA6.HTM
> 
> The lightning flash lasts about 100ms
>> http://hyperphysics.phy-astr.gsu.edu/hbase/electric/lightning2.html#c2
> 
> The way these shots are done at night is you just leave the shutter open (B) 
> and stop it down a bit. That gives you a long exposure time. When the flash 
> occurs, close the shutter. 
> 
> In the daytime, they use a neutral density filter. Same basic technique.
> 
> To do what you want to do will require an external camera shutter. Some can 
> fire in under 20ms.
> 
> Uman has a few books on lightning. Well worth the money.

the camera has shutter lag of 40ms or less, so it won't be too slow. 
Lightning really isn't all that fast, I just want an electronic trigger 
system that only triggers the camera when a flash of light of the correct 
speed and intensity appears. It's fairly bright in Chicago so long 
exposures when you're inside a storm mostly pickup reflected light from 
the city itself, which is an ugly orange color. Yeah one could use blue 
filter and all that, but it's still very bright.

Cloud to cloud lightning causes lots of lower intensity flashes which I'd 
like to just tune out so to speak as there's nothing to see there but a 
flash of diffused light.

I will look for the book though.

haiticare2011@gmail.com wrote:
> On Tuesday, June 24, 2014 6:46:25 PM UTC-4, the rain in spain. wrote:
>> Buy one of the consumer digital cameras that has a SDK. Set it to record video for 20-30 seconds at a time, and wait for a input from your flash detector via serial or USB. If there was a flash, save or download the video. If not, start recording again.
>> 
>> 
>> 
>> Steve
> 
> Yes, that's clever. An even simpler way is to not use a detector. Do time lapse 
> photography every night, each 20 s. long, and if a thunderstorm happens, review 
> your photos. If not, erase the photos. (total chip erase.)
> 
> simple. easy.

this might be ok out in the country, but 20s exposures are going to pick 
up too might stray light in a major city.

It may be possible to set a super low ISO in the camera and use a super 
dark ND filter to attentuate the garbage light, but for the hell of it, I 
want an electronic solution vs. brute force. I've not found a screen cap 
from an oscilliscope of the light intensity of a lightning flash as 
measured by a photodiots. This would be interesting to see.

Cydrome Leader wrote:


> 
> the camera has shutter lag of 40ms or less, so it won't be too slow.
> Lightning really isn't all that fast, I just want an electronic trigger
> system that only triggers the camera when a flash of light of the correct
> speed and intensity appears. It's fairly bright in Chicago so long
> exposures when you're inside a storm mostly pickup reflected light from
> the city itself, which is an ugly orange color. Yeah one could use blue
> filter and all that, but it's still very bright.


Are you sure that 40ms isnt that "trigger button halfway down" mode? Most 
cameras are in a sleep mode when just sitting there in manual. The link on 
this Mk III shows this (model specific of course). 

The stepped leader has a number of 1us pulses. That is what you would want 
to trigger on. There is a very high frame rate video of a lighting strike on 
the internet, but I can't find it at the moment. Too many false hits on 
google. The stepped leader is not as bright, but the very short duration 
steps would make for a good trigger, giving you some advance notice before 
the return strike hits. The video wasn't on youtube, but hosted on the 
authors website. I snagged a copy of it with a little hacking, but I need to 
locate the file.