Technical Synopsis
This project is in the prototyping stage and is intended to give Bluetooth Low Energy capabilities to vintage film cameras.
The BLE Shutter Release will allow a user with a smart device to control the shutter at a distance. The user will be able to activate the shutter via a time delay. If the camera supports bulb mode, the user can take accurately-timed long-exposures for night photography or astrophotography.
When complete, the device will attach to a camera’s accessory shoe and threaded shutter button.
Altium Designer is the CAD tool used to produce schematic and layout documents and 3D renderings.
Below are the documents produced during the creation of the project.
Prototype Results – Work In Progress.
Background
There is a growing market consisting of users of vintage medium format and 35mm film cameras. These cameras lack many useful features found on modern professional and “prosumer” digital cameras that make the life of the user much more comfortable, though are capable of taking higher quality photographs than digital.
The most uncomfortable issues are the result of controlling exposure over time. Exposure is controlling the amount of light that hits the light sensitive part of film that creates the film negative once developed. In low light photography, lack of control can result in a poorly exposed negative, or worse: motion blur due to camera shake, as seen below.
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There are two primary ways this issue is dealt with in the digital space. The first is by being able to vary the ISO, or sensitivity, of the sensor. By increasing sensitivity, you can decrease exposure time to remove blur from motion or camera shake. With a film camera, you are stuck with the ISO rating of the film you placed into the camera.
The second way digital deals with this issue is removing the primary cause of camera shake: human touch. Adding an option to add a timed delay from when the shutter button is pressed and the shutter is actually fired allows the camera to settle from the disturbance of touching the camera.
For extreme low light photography, high end digital cameras allow the user to select exposure times much greater than the one second limitation of a mechanical movement shutter. Most vintage cameras have a mode where the shutter is seperated from the timing mechanism, allowing the shutter to be open as long as the shutter button is pressed.
Holding the shutter button in, of course, introduces camera shake as the user has to hold the button in for the duration of the exposure. Exposure times could be tens of seconds to minutes, or even hours for astrophotography, which adds fatigue.
For studio / flash photography, a hands free approach is best. Most professional level digital cameras allow wireless operation with dongles that attach to a either a proprietary connector or a USB port on the camera.
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Existing Solutions
There are no existing solutions available on the market today with the exception of manually operated shutter release cables.
Two hobbyist solutions exist on the internet, but suffer from the same faults. Their wireless capabilities are extremely limited. More than one device cannot operate in the same range and the signal can be easily hijacked. The device itself is big and ugly.
The remote itself is another piece of kit that must be carried. For photography in the field, less is more. The remote could be forgotten. Needing space for two items could mean there is not enough room in the bag and it will be left behind. Both parts of the device will require its own set of batteries, exacerbating the problem.
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User Needs
- Field replaceable battery
- Small / lightweight
- Attachable to camera accessory shoe
- Attachable to camera shutter via universal cable
- Limited support gear
- Wireless communication
- Multiple devices able to operate within proximity
- Secure communications
My Design
Technical Details
Power was decided to be based around the CR-P2, a 6v lithium battery common to photography applications. This is used to create two power rails: 4v8 – 5v for the servomotor, and 3v3 for the MCU. To save power, the rail to the servomotor is turned off by the MCU until the servo is needed.
The MCU is an NXP QN9080SIP. This was chosen for its built-in BLE radio and antenna, as well as being an ARM Cortex M4 core with the required I/O and ADC capabilities. Its extremely small size and low power requirements were also appreciated.
A soft switch circuit was designed to allow only a single push switch to be able to turn on the device and provide input for the MCU. This was realized with the addition of two NPN and one PNP transistors. The circuit can be seen in the Prototype Results document below.
A current sense circuit is located on the low-side of the servomotor. This was added at first to allow shutdown of the servo if there was a block condition on the motor. However, after testing it became apparent that different throw sizes of the releases on different cameras required adjustment of the travel of the servomotor. Instead, a control system was developed to continuously monitor the state of the servo to determine if the shutter is being released and adjusting travel as needed.
Below is the system flow diagram for the implemented solution.
For more technical information, such as schematic drawing, bill of materials, or design layout, please view the document below.