Flash hacking for High Speed Photography - Page 1
Forum section: electronics / projects

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 02, 2016, 07:37:10 am
content: Here's a small hack I did about 10 years and thought it might be nice to share.I wanted to take high speed photographs of events happening very quickly, ie much less than a milisecond. For those of you interested in the method, these pictures can be taken with a DSLR camera but the actual picture is "shot" with a high speed flash, that is the shutter of the camera is set to 5 or 10secondsin a dark room , whereas the flash lights up the scene during a few microseconds. The process is as follows:1) prepare the setup2) turn off the lights of the room3) press the camera shutter, it will remain open for a few seconds4) create the event you want to photograph (ie breking of a glass bottle)5) sense the event and trigger the flash accordingly6) camera shutter closes7) turn on light and inspect the results O0The problem is that these special flashes are expensive, so back in the day I decided to hack a cheap flash and turn it into a high speed one.I did this basically by sensing the light coming out of the flash and turning off its current after a delay. I have rescued the schematic and posted it below along with some results from my at the time 8Mpixel Nikon DSLR.Don't ask me much about the circuit it as I don't remember much as to why I did design it that way, I was young and sloppy

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 02, 2016, 07:42:45 am
content: more pics and schematic...

author: AndyC_772
author_rank: Super Contributor
timestamp: June 02, 2016, 07:49:00 am
content: I just set my Canon flash to minimum power; you get a much shorter flash that way.The fun part is triggering at the right time, which I did with a circuit incorporating a microphone, a comparator and a variable delay. (No schematic, I'm afraid... it was a bit of a lash-up I used to fill time during a quiet period at work).

author: PartialDischarge
author_rank: Super Contributor
timestamp: June 02, 2016, 01:48:48 pm
content: Quote from: AndyC_772 on June 02, 2016, 07:49:00 amThat's a trick useful for a exploding water balloon, since its a somewhat slow event, but for something speedier like a bullet....As the light pulse gets shorter, you actually need more light intensity in order to keep the exposure in the CCD sensor at an appropriate level.Moreover, the rising and falling edges of the light pulse will determine the 'sharpness' of the picture.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 02, 2016, 02:30:29 pm
content: I love photos like these. There is so much physics and geometry to decode in the images.

author: zlymex
author_rank: Frequent Contributor
timestamp: June 02, 2016, 02:39:36 pm
content: Very good, and some very nice photos.I did the same thing 14 years ago and there is no DSLR available at that time(or I cannot afford one) so I use Nikon E4500.I also use a laser pointer, a photo diode and b=variable digital delay to trigger two flashes which modified to flash in less than 5uS.

author: tautech
author_rank: Super Contributor
timestamp: June 02, 2016, 02:41:23 pm
content: Quote from: CatalinaWOW on June 02, 2016, 02:30:29 pmYep, this gun nut has subscribed.