The HDR and interval trigger

Description: This article explains how to build the second improved version of the HDR-Jack. In contrast to the original circuit, this version is powered by a lithium coin battery. This results in compatibility with cameras not supported by the first version due to the focus wire issue. The circuit can be easily embedded in the enclosure of a cable remote controller as shown in the pictures below. The original function of the cable release is preserved. The following table lists all functions of the HDR-Jack 2, which are activated by pushing the small "extra" button. Modes 1 to 5 provide different bracketing series and an interval function. Modes 6 to 17 allow the configuration of the trigger. This is the all-purpose bracketing series with an EV step of 2. The nominal exposure times are 1/125, 1/30, 1/8, 1/2, 2, 8, and 30 seconds. The shortest time may vary significantly depending on the camera. The hold time of the button is used as the interval period, with a duty cycle of approximately one. For example, holding the button down for 4 seconds results in a trigger sequence with 2 seconds on and 2 seconds off. This is a short bracketing series for daylight conditions with an EV step of 2. The nominal times are 1/200, 1/60, 1/15, 1/4, and 1 second. The shortest time may vary significantly depending on the camera. This is a short bracketing series for daylight conditions with an EV step of 1. The nominal times are 1/200, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2, and 1 second. The shortest time may vary significantly depending on the camera. This is the all-purpose bracketing series with an EV step of 2 and mirror lock-up support. The nominal exposure times are 1/15, 1/4, 1, 4, 15, and 60 seconds. This is the all-purpose bracketing series with an EV step of 1 and mirror lock-up support. The nominal exposure times are 1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8, 15, 30, and 60 seconds. Using these functions, the time gap between the exposures in the bracketing sequences can be changed. The value is saved permanently in the EEPROM of the microcontroller. This feature has been implemented to optimally exploit the capabilities of the camera in use and keep pace with technological developments. Setting a larger gap provides the opportunity to check the histogram in the preview after each exposure, allowing for the possibility to abort the bracketing and save time. The minimum bulb exposure time of some camera models may be longer than the times provided by the HDR-Jack 2, which can result in skipped shots or jumping exposure times. To avoid unnecessary waiting or unusable shots, the shortest times can be skipped according to the description in the table. The limiter is also practical if the first shots result in the same exposure level. These functions allow for modifications in how the trigger pulse is generated. Different camera models exhibit varying behaviors depending on how the trigger signal is applied. DSLRs of the EOS xxxD series and the 1000D show the best reproduction of the nominal exposure times when triggered using the shutter wire only. In contrast, the EOS 40D requires both wires for bulb exposure. The interval mode does not require special settings on the camera. It is recommended to use manual focusing, especially for dark scenes, to avoid missed triggers caused by focus hunting. The HDR-Jack 2 utilizes bulb mode to control the exposure time. This straightforward principle avoids complicated protocols and is compatible with many camera types, but it also has its limitations. The most significant limitation concerns the minimum exposure time. The shortest exposure time observed with a Canon DSLR in bulb mode is approximately 1/200 seconds. With other brands, this time can be even longer (measured at 1/10 with Nikon D80, 1/8 with Sony a350, and reported at 1/60 with Pentax). Unfortunately, it is not feasible to control the camera accurately at very short times. Older Canon cameras without live view seem to perform better than newer models. For live view types from Canon, exposure times shorter than approximately 1/4 seconds become problematic.

The HDR-Jack 2 circuit is designed to enhance the functionality of camera remote triggering, particularly for bracketing photography. The integration of a lithium coin battery allows for a compact design, making it suitable for embedding within a cable remote control enclosure. The circuit retains the original cable release function while introducing advanced features that cater to a broader range of camera models.

The microcontroller at the heart of the HDR-Jack 2 enables the selection of various exposure modes through a simple user interface, activated by a dedicated button. Each mode offers unique bracketing sequences that photographers can customize based on their specific needs. The EEPROM storage allows for persistent settings, ensuring that users do not have to reconfigure the device for each use.

The bracketing series provide a systematic approach to capturing multiple exposures at different settings, which is particularly useful in high dynamic range (HDR) photography. The ability to adjust exposure times and intervals allows for greater creative control, enabling photographers to optimize their shooting conditions.

The circuit's design considers the variability among different camera models, particularly regarding the trigger signal application. By accommodating these differences, the HDR-Jack 2 enhances compatibility and performance across a range of devices, including DSLRs and mirrorless cameras.

In summary, the HDR-Jack 2 is a versatile and user-friendly device that significantly improves upon its predecessor by offering enhanced features, compatibility, and ease of use for photographers seeking to explore advanced bracketing techniques.This article explains how to build the second improved version of the HDR-Jack. In contrast to the original circuit this version is powered from a lithium coin battery. This results in compatibility with cameras not supported by the first version, because of the focus wire issue. The circuit can be easily embedded in the enclosure of a cable rem ote controller as shown in the pictures below. The original function of the cable release is preserved. The following table lists all functions of the HDR-Jack 2. They are activated by pushing the small "extra" button. Modes 1 to 5 provide different bracketing series and an interval function. Modes 6 to 17 allow the configuration of the trigger. This is the all-purpose bracketing series with an EV step of 2. The nominal exposure times are 1/125, 1/30, 1/8, 1/2, 2, 8 and 30 seconds. The shortest time might vary strongly depending on the camera. The hold time of the button is used as the interval period. The duty cycle is approx. one. Example: Holding the button down for 4 s results in a trigger sequence with 2 s on and 2 s off. This is a short bracketing series for daylight conditions with an EV step of 2. The nominal times are 1/200, 1/60, 1/15, 1/4 and 1 second. The shortest time might vary strongly depending on the camera. This is a short bracketing series for daylight conditions with an EV step of 1. The nominal times are 1/200, 1/125, 1/60, 1/30, 1/15, 1/8, 1/4, 1/2 and 1 second. The shortest time might vary strongly depending on the camera. This is the all-purpose bracketing series with an EV step of 2 and mirror lock-up support. The nominal exposure times are 1/15, 1/4, 1, 4, 15 and 60 seconds. This is the all-purpose bracketing series with an EV step of 1 and mirror lock-up support. The nominal exposure times are 1/15, 1/8, 1/4, 1/2, 1, 2, 4, 8, 15, 30 and 60 seconds. Using these functions the time gap between the exposures in the bracketing sequences can be changed. The value is saved permanently in the EEPROM of the microcontroller. This feature has been implemented to optimally exploit the possibilities of the camera in use and keep step with the development. Setting a larger gap gives you possibility to check the histogram in the preview after each exposure so you can abort the bracketing and save time.

The minimum bulb exposure time of some camera modells might be longer than the times provided by the HDR-Jack 2. The effects are skipped shots or jumping exposure times. To avoid unnecessary waiting or unusable shots, you can skip the shortest times according to the description in the table.

The limiter is also practical if the first shots result in the same exposure level. These functions allow to change the way the trigger pulse is generated. Different camera modells behave differently depending on how the trigger signal is applied. DSLRs of the EOS xxxD series and the 1000D show best reproduction of the nominal exposure times when triggered using the shutter wire only. In contrast, the EOS 40D needs always both wires for bulb exposure. The interval mode requires no special settings on the camera. It is recommended to use manual focusing especially for dark scenes to avoid missed triggers caused by focus hunting.

The HDR-Jack 2 uses the bulb mode to control the exposure time. This very simple principle avoids complicated protocols and is compatible with many camera types, but also has its limitations. The biggest one concerns the minimum exposure time. To my knowledge, the shortest exposure time observed with a Canon DSLR in bulb mode is about 1/200 s.

With other brands this time becomes even longer (measured 1/10 with Nikon D80, 1/8 wit Sony a350, heard of 1/60 with Pentax). Unfortunately it is not possible to control the camera properly at very short times. Older Canon cameras without live-view seem to perform better than newer ones. For live-view types from Canon exposure times shorter than approx. 1/4 s beco