Precision Chronometry: Film Shutter Speed Tester

A vintage 1970s film camera shutter is purely mechanical—a complex mess of physical springs and sliding titanium plates. Over decades, those springs fail. The Shutter Speed Measurement Tester forces the Arduino to operate entirely at the microsecond temporal scale, utilizing intersecting dual-laser physics to mathematically prove if "1/1000th of a second" on the camera dial is actually mechanically accurate!

The Dual-Laser Gate Physics

You cannot use a simple Light Dependent Resistor (LDR) for this. An LDR takes nearly 2 milliseconds to wake up, which is infinitely too slow to measure a fast shutter!

1. You must utilize extreme-speed Phototransistors (like the BPW34 or PT334), which have a nanosecond-level response time.
2. We place a laser diode on one side of the camera, and the phototransistor directly behind the camera lens on the other side.
3. You trigger the camera shutter! The physical titanium curtain slides open. The laser violently strikes the phototransistor!

Catching the Pulse (The micros() clock)

The Uno's millis() function is too coarse. We must dig deeper into the ATmega registers using micros().

• The Execution Variables:

unsigned long startTime = 0;
unsigned long elapsedTime = 0;

void loop() {
  if (digitalRead(LaserSensor) == HIGH && startTime == 0) {
     startTime = micros(); // The exact nanosecond the blade opened!
  } else if (digitalRead(LaserSensor) == LOW && startTime > 0) {
     elapsedTime = micros() - startTime; // The blade closed! Calculate the gap!
     calculateShutterTarget(elapsedTime);
     startTime = 0; // Reset for next shot
  }
}

• If the elapsedTime returns 1000 microseconds, the Arduino mathematically divides by a million, outputting an absolutely flawless 1/1000 sec onto the LCD screen!

Optical Sensor Configuration

• Arduino Uno/Nano (Sufficient, but requires clean code with zero delay() functions blocking the loop).
• Extremely fast NPN Phototransistor Diodes. (Do NOT use cheap generic LDRs or Photoresistors, they will drastically skew the high-speed math).
• Basic 5mW Laser Diodes (To generate a fiercely bright, ultra-focused beam capable of passing straight through complex camera lens glass elements).
• A 16x2 I2C LCD Character Display for clean workbench readout.