Highspeed photography 101 – Lesson 8

Highspeed Photography 101

Table of contents

Introduction
Lesson 1: Freeze the motion with your shutter
Lesson 2: Freeze the motion with your shutter II
Lesson 3: Freeze the motion with your flash
Lesson 4: A small but powerful helper: Arduino
Lesson 5: Trigger your camera with an Arduino
Lesson 6: Trigger your flash with an Arduino
Lesson 7: Working with sensors: Light barrier
Lesson 8: Working with sensors: Sound trigger

Lesson 8: Working with sensors: Sound trigger

Introduction
In the last lesson I wrote about light barrier. Sometimes there are sensors which are more adequate than a light barrier f.ex. if you want to photography a bursting balloon. In this lesson I’ll show how to use a sound trigger.

Broken glass

Idea
As we saw in the last lesson in most cases there is not a correct or a wrong trigger. One can solve a problem with different approaches and finally its the decision of the photographer, which trigger he chooses.
In highspeed photography sound trigger and light barrier are often used. For this reason, I’d like to have a look at both triggers. If you understand the principle then you should be able to use other triggers.

Equipment
– Cam
– Flash
– Wireless remote for flash (optional)
– Arduino
– Sound trigger kit (hiviz.com)

Camera- / flash settings
How to setup the camera for this kind of photos is described in detail in lesson 3. How to connect and trigger a flash with an Arduino is described in lesson 6. For this kind of photo we don’t use any special flash mode as HSS or ‘repeating flash’. We setup the flash to trigger ‘normally’, just once, with very low power settings. (Remember: The lower the settings the shorter the flash duration)

Arduino
The basic Arduino setup is the same as in lesson 6 but this time we’ll connect a sound trigger. As in lesson 7 the sound trigger is from hiviz.com (about 20$).
Again we connect the output of the sound trigger with an analog input of the Arduino. With the hiviz.com sound triggers the output is on the anode of the SCR. (Until version 10: Row 16 F-J, version 10: Row 9 A-E).

Arduino with sound trigger

We’ll setup the Arduino to trigger the flash as soon as there is a signal from the sound trigger. (The code is the same as in lesson 7).

//hiviz connected here
int signalPin = 4;
//flash connected here
int flashPin = 11; 

//delay between signal from sensor and firing flash
int preflashdelay = 0; 

//delay after flash until the unit shall be ready again
//usually I put the exposure time, to ensure that
//I don't have unwanted multi exposures
int postflashdelay = 5000;

// The setup() method runs once, when the sketch starts
void setup()
{
  // initialize the flash pin as an output:
  pinMode(flashPin, OUTPUT);
  //setup serial console
  Serial.begin(9600);
}

// the loop() method runs over and over again,
// as long as the Arduino has power

void loop()
{
  //Read value from signalPin
  int reading = analogRead(signalPin);

  //print reading
  Serial.println(reading);    

  //if we're about a certain value
  if(reading > (55)){

    //debug output
    Serial.print("Flash triggered @ ");
    Serial.println(reading);

    //sleep for preflash delay
    delay(preflashdelay);

    //fire flash
    digitalWrite(flashPin, HIGH);
    delay(50);
    digitalWrite(flashPin, LOW);

    //sleep for postflash delay
    delay(postflashdelay);
  }
}

One of the advantages of the sound trigger is that you don’t have to put it a bit further away from the object. Especially if you’re dealing with liquids you can prevent the electronics from getting wet.

Taking the picture
I described the process of taking the pictures already multiple times: Turn of the light, start the cam, break glass / burst balloon…, flash, cleaning.

Conclusion
As we see the difference between the light barrier and the sound trigger is minimal. You should be able to connet other sensors like accelerometer based on the information from the last two lessons.

Retrospect
This is the last lesson of the highspeed photography 101. I’d like to retrospect and show what my basic considerations are when I take a highspeed photo.
Lesson 1-3: Describing some basic techniques of highspeed photography. At the start of a highspeed photo I think about which of theses techniques to choose.
Lesson 4: Basic knowledge of the Arduino. Lesson 5-8 will use this knowledge.
Lesson 5/6: Depending on the chosen technique I decide whether to trigger the camera or a flash.
Lesson 7/8: Depending on the situation I decide to use sensors. In those two lessons I wrote about light barrier and sound trigger, but you should be able to use any sensor based on that information.

If there are questions or if you need help with your highspeed photos, you can always contact me.

Finally I’d like to thank
– everybody who helped me
– everybody who sends picture using this techniques
– everybody who views/comments/faves my pictures
and special thanks to you, the reader of those tutorials.