SmaTrig 2.1

DIY for Photography


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This is the project home page of the SmaTrig 2.1, the improved version of the the SmaTrig 2. On this site you will find complete instructions how to use and build the versatile 15-in-1 camera trigger SmaTrig 2.1. Everything needed to build the device is provided including the PCB design, firmware, drill plans, etc. The SmaTrig 2.1 is based on an AVR microcontroller, and is equipped with sensor circuitry for detecting sound and light pulses for capturing lightnings or high-speed photography. The 15 functions can be divided into four groups: bulb mode bracketing programs for HDR photography, interval and timer modes, sensor modes and other functions like manual camera triggering or configuration. Many of the modes have some hidden advanced options, but I paid great attention not to obscure their usability. Ritual instruction manual spurners can use the SmaTrig just using their intuition.

This article is a guide how to build a homebrew high-speed photoflash unit. Compared to commercially available devices this flash will offer a much shorter flash duration allowing to reduce the motion blur greatly. With about 2 microseconds flash time it's about 30 times 'faster' compared to a standard flash gun set to 1/64 output power. The difference is demonstrated in the two images below, where a router bit was photographed at 30000 rpm. The presented project is intentionally kept DIY-friendly by using easily available parts and "low-frustration" technologies. The low tech approach also pays out if you need several units. Please note that the circuit is designed for 230 V and will not work properly in 110 V grids without modifications. There are voltages above 1000 V in the device. Make sure, you have enough experience with electrical circuitry if you plan to build the flash unit!

The presented circuit combines two functions often needed by photographers. It can operate as a splitter or multiplier and allows connect three (up to 6 with splitters) different photo flashes to a camera or radio control. It's capable of triggering older high voltage photo strobes or mixing new and old devices. The second function is less known but very practical when objects are to be isolated form the background. This is a typical task for a product of stock photographer. The image is built in two steps: a traditional well illuminated image of the object, and a second image of the background with a black silhouette of the object. The background image serves now as a mask for the first one. The essential thing now is to have the images matching. Any movement of the (human) object make the mask useless.

Setups for high speed or animal photography often require a light barrier to detect the object of interest. Laser barriers offer very high precision and an easy adjustment of the beam, but have the disadvantage of using visible, usually red or green light. It happens easily that the laser spot is accidentally captured during the exposure and ruins the photo.

In diesem Tutorial wird der Einsatz einer Laser-Lichtschranke zur Fotografie eines sich bewegenden Objekts, z.B. eines Tieres erläutert. Der technische Aufbau ist auf viele Szenarios übertragbar, bei den das Fotomotiv zu einem unbestimmten Zeitpunkt auftaucht und das manuelle Auslösen nicht zum Erfolg führt. Als Hardware wird eine Laserwasserwaage und der SmaTrig verwendet, eingestellt auf die entsprechende Funktion.
Als Beispiel dient das Bild einer springenden Ratte wie im Titelbild dargestellt. Die Entstehung des Fotos wird im Folgenden aus technischer Sicht ausführlich erläutert. Warum gerade eine Ratte? Ratten sind sehr neugierig und haben erstaunliche motorische Fähigkeiten. Sie lassen sich relativ einfach zu einem Sprung in Richtung ihres Lieblingsfutters überzeugen. Ist der Weg einmal gelernt, ...

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Fotografisches Equipment ist fast immer mit einer Möglichkeit zur Befestigung auf einem Stativ ausgestattet. Dabei kommen zwei Gewinde zum Einsatz. Wie die genauere Betrachtung verrät, handelt sich um ein untypisches Gewinde, nämlich ein Zollgewinde mit einer größeren Steigung als unsere metrischen Gewinde ähnlicher Größe wie M6 oder M8. Im Titelbild oben ist das kleine Fotogewinde mit einer M6-Schraube verglichen.
Das kleinere Gewinde wird in Kameras bis zu der Größe einer DSLR verwendet. Das größere ist an Mittelformatkameras oder schweren Stativen zu finden. Auch Mikrofon- und Bühnenstative verwenden diese Größe.

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In this short review I describe the Yongnuo RF603 ii from the technical point of view focusing mainly on two topics difficult to test without specialised equipment: the trigger lag and the power consumption of the devices.
The Yongnuo RF603 ii radio remote release became quite popular under photographers recently. It offers all the amateur needs at a reasonable price. It has various connection options like the flash hot shoe, a 2.5mm jack connector and the PC sync plug. It uses standard AAA batteries in it's mk2 version. Something really great is the possibility to trigger Yongnuo's YN560-iii flash unit directly. None of the big camera manufacturers came up with this simple idea. They prefer to use their master-slave pre-flesh communication and hide this feature in less expensive camera models.

Although a photo-flash fires much faster than a camera, the timing might become critical for high-speed photography. Below you will find the flash duration and the trigger lag numbers for the popular Canon Speedlite 430EX (year 2009). To interpret the oscilloscope screen-shots it's important to understand how a modern photo flash unit controls the output power. Instead of wasting one part of the energy to reduce the light output in modern devices like the 430EX the discharge is interrupted by a transistor (IGBT). The remaining energy in the photo flash capacitors can be used for the next flash reducing the charge time. Only in the 1/1 output setting the whole energy in the caps is discharged. Let's have a look on the flash duration diagrams. They were taken with a simple photo diode (SFH208P) loaded with a resistor of around 500 Ohm for a fast response. The amplitudes are not of importance here. The scope was triggered by the falling edge of the trigger voltage after short-circuiting the trigger pin of the flash unit.

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Inspired by the beautiful falling drop images that become popular in the net I also purchased a magnetic value to make some experiments. Having already the SmaTrig and the delay circuit the olny missing element in the drop photography chain was a circuit converting the low current trigger signals into a high current power signal driving the magnetic valve. This component is usually referred to as a servo, just like in a car. Such a switch comes in handy whenever heavy lights, solenoids, valves, motors, heaters or big relays have to be controlled by photographic circuitry, a microcontroller or other logic level circuitry.

image processing
Many people stil think that Linux is monochrome and you can't even display an image. On the fist glance the image processing potential under Linux may seem a little limited compared to those of Windows. But when it comes to automised image processing, things look totally different and the command line is a mercy. You just have to know the commands and options...
In the following I've put together some useful commands for image processing that I used again and again in the last few years. They might be interesting for the technically oriented, ambitioned DSLR user working under Linux.

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This article describes a uC based delay circuit for photographic applications like drop or high speed photography. It can be used to control the trigger lag of cameras or flash units. The input and output of the circuit use standard 3.5 mm jack connectors, so the delay element can be looped into your existing trigger circuitry like the SmaTrig for example.
As simplicity and budget components were important design goals, there is no text display or any sophisticated analog input stage. The circuit allows three delay ranges which are indicated by LEDs.

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On this site you will find a complete instruction how to build a versatile 15-in-1 camera trigger, the SmaTrig 2. Everything needed to build the device is provided including the PCB design, firmware, drill plans etc. The SmaTrig 2 is the second improved version of the multi-purpose 15-in-1 smart camera and flash trigger SmaTrig (1). Compared to the old version, it boasts some completely new features. The existent one have been optimised for better usability. The enclosure hasn't changed, so the trigger is still very compact having the size of a match box.

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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 remote controller as shown in the pictures below. The original function of the cable release is preserved.

Camera remote release pinout list
Most DSLR and SLR cameras can be triggered remotely using a release cable. Unfortunately the connectors used for the external release have rather exotic shapes. Below you will find the pinouts for the common camera types. The standard solution consists of three wires: ground, focus and shutter. To focus the camera the focus wire has to be connected to ground. To release the camera both wires have to be connected to ground.

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In the following the inner workings of a no-name Canon EOS 350D/400D battery grip will be shown. My motivation to disassemble the grip came from the idea to gain control of the camera buttons and wheels without opening the camera body. By connecting a microcontroller to the dial wheel and the shutter button in the battery grip, functions not included in (or intentionally excluded from) the camera firmware, such as unlimited exposure bracketing, can be implemented.

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This article explains how to build an ultra-compact AVR controlled multipurpose trigger for Canon EOS cameras with a remote control jack connector (e.g. EOS 350D, EOS 400D, EOS 450D, EOS 1000D). The trigger features an interval function (intervalometer) for time lapse photography, a HDR trigger mode for shooting exposure bracketing image series, a bulb mode for astronomy or high-speed photography and a delayed trigger option for long exposure photography. The complete circuit is accommodated in the 2.5 mm jack plug needed to access the remote trigger connector. It's so small you can use it as a key fob.

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Experiments with the external trigger function in my EOS 400D inspired me to develop a simple do-it-yourself sound trigger. The circuit detects sound pulses that exceed a certain pressure level.
The sensitivity of the trigger is limited, but high enough to detect popping champagne bottles, bursting balloons or eggs hitting the floor. It can trigger cameras as well as flashes, as both are activated by the same mechanism of short-circuiting two wires.

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After triggering a camera (mechanically or electrically) it takes a certain time until the shutter opens and the exposure can begin. This delay is called the shutter lag. The values vary strongly depending on the camera model. The focusing time is not considered in this test. In all test images the focus was adjusted manually for fastest response times.
There are several ways to determine the shutter lag of a camera such as photographing falling objects, rotating discs or an electronic counter. I chose the digital method, due to a simple implementation and good readability of the results...

The EOS series of cameras from Canon offer a nice feature which is of particular interest for DIYers and technically oriented photographers. It is possible to trigger these cameras externally using an electrical signal. To the hobbyist's delight Canon used a customary jack plug instead of an exotic system connector. There is no special protocol needed to trigger the camera - you just have to short-circuit two wires. Knowing this, building a homebrew Canon RS-60E3 wired remote control is a snap! Or maybe an interval trigger, or a microcontroller based...

Canon RC-1 communication protocol
This article describes how the Canon RC-1 infrared remote control communicates with the camera. To figure out the protocol I used an IR photo-diode first. Because of the bad signal quality I decided then to disassemble the RC-1 and measure the IR-LED voltage directly. I used the occasion and took some pics of the circuit...

Canon RC-1 inside
This article describes how to build a DIY low-budget AVR-based infrared remote control for Canon cameras. The reverse-engineered communication protocol of the RC-1 is described here. The RC-1 lets you trigger the camera instantly or with a delay of 2 seconds from a distance of up to 5 meters (~16 ft). It comes in very handy when taking long exposure pictures or for HDR photography. The presented circuit can be used as part of DIY interval triggers for smaller Canon cameras without the external trigger connector. In bracketing mode the RC-1 lets the camera shoot a whole series of images at once...

The SmaTrig is a compact, microcontroller based multi-function camera or flash trigger. Its 15 modes of operation make it come in handy in many situations. It is equipped with sensors for light and sound for capturing short-duration events. The only connection with the camera is the external trigger plug. There is no need to modify the camera in any way. The circuit is powered by an integrated coin cell...

Exposure Diagram
The diagrams below depict the exposure level for different exposure times and aperture numbers for the Canon EOS 400D + EF-S 18-55 and constant light conditions. On the x-axis of the diagram the exposure time is plotted. A log-scale was chosen for more convenient visualisation. The y-axis represents the aperture number as chosen in the camera (linear scale). The isolines depict the mean exposure level of the images averaged over all pixels. The images have been converted from RGB to greyscale before averaging...

When photographing drops, the first problem to overcome is to build an apparatus which emits drops with a stable interval. This article describes how to build a very simple yet elegant drip apparatus (also called a dripper, emitter or just drop generator). The construction is rather trivial. The setup is show in the picture below. The materials you need are...