This DIY Kit Can Automatically Test Film Cameras Using an Arduino Nano

Film camera anatomy

With the explosion of digital cameras, the equipment required for taking care of film cameras had gradually decreased and/or become more expensive. Oftentimes, testers for this camera technology consist of time counting methods which use a light source and a detector to do everything from measuring shutter speed to determining how long it takes for the flash to activate. Alternatively, exposure values can be found by utilizing light accumulation methods that see how much light falls on a sensor over a known window of time. All of these measurement points are vital for calibrating the timers and shutter of a film camera which can create a more realistic image.

The goal

In order to capture all of this data in an accurate manner, GitHub user srozum set out to build a DIY testing rig that could collect light readings, perform calculations based on certain parameters, and then present it to the user — all while using inexpensive parts and being open source. His design included measurements for exposure time/strengths, data averaging over multiple trials, automatic sensor detection, an accuracy of 10 microseconds, and a range of speeds from one second down to 1/8000th of a second.

Required components

To meet the stated goals, srozum began by gathering a series of components for his device. At the center is an Arduino Nano-compatible board which runs the firmware for controlling the sensors and display. Next, a 20x4 LCD screen was added so that users could select different options via a keypad and then see the results immediately. Lastly, he created three sensors for taking the readings and sending data back for processing.

The main board

The primary PCB houses the Arduino Nano, an unregulated 24V input jack, an unregulated 7-12V input jack, a mini buck converter for knocking down the voltage to 5V, and a wide assortment of connectors. The first socket, called "Socket A," exposes power, GPIO pins, and an ID pin. That last pin is used by the Nano to determine which sensor is attached and helps to prevent accidental misconfigurations. The second "Socket B" connector differs only slightly from the first in that it has an I2C bus exposed. The light unit, keypad, and LCD boards all have their own headers as well.

Adding some sensors

The entire purpose of this automated testing tool was to take measurements, and for that, it needed some sensors. The purpose of sensor #1 was to house a series of three SIC553-04 photodiodes and measure their output via a single analog pin each. In doing so, the evenness of lighting that hits the film at any given moment can be quantified and used in conjunction with the frame area to give the exposure values and timings.

The second sensor was essentially identical to the first and only differed by having a single photodiode rather than three. Finally, the last sensor can be connected to the camera's Flash Sync port and used to measure the delay between the flash activating and the shutter opening to take a photo.

Using the tester

This specialized device not only has inexpensive components and great accuracy, but also extensive documentation on GitHub about how it operates. When booted, one of eight test modes can be selected and used with a compatible sensor. Additionally, the settings menu has the ability to adjust parameters such as the speed range, number of samples, and the size of the frame, all of which are saved to EEPROM for later retrieval.

To read more about this project, you can visit its GitHub wiki page or view it on Tindie here.