De Wet Erasmus Photography III
Theory Essay: High Speed Photography
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High Speed Photography (HSP) is the science of taking pictures of very fast phenomena. In 1948, the Society of Motion Picture and Television Engineers (SMPTE) defined high-speed photography as any set of photographs captured by a camera capable of 128 frames per second or greater and of at least three successive frames. In common usage, high speed photography may refer to either or both of the following meanings. The first is that the photograph itself may be taken in a way as to appear to freeze the motion, especially to reduce motion blur. The second is that a series of photographs may be taken at a high sampling frequency or frame rate. The first requires a sensor with good sensitivity and either a very good shuttering system or a very fast light. The second requires some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly. In common usage, high speed photography may refer to either or both of the following meanings. The first is that the photograph itself may be taken in a way as to appear to freeze the motion, especially to reduce motion blur. The second is that a series of photographs may be taken at a high sampling frequency or frame rate. The first requires a sensor with good sensitivity and either a very good shuttering system or a very fast light. The second requires some means of capturing successive frames, either with a mechanical device or by moving data off electronic sensors very quickly. There are a few challenges to capturing rapidly occurring events. Whether you're trying to freeze a bullet passing through a piece of fruit, a pin popping a balloon, or a light bulb shattering, you need to be able to capture an event occurring within a thousandth of a second or less. Actual high speed photography rigs are quite pricey, but you can easily emulate more expensive rigs with a standard DSLR by using creativity and common photographic theory.
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To work around the problems with shutter lag and flash synchronization, the exposure is done in a completely dark room. This way the shutter can opened without actually getting an exposure. The exposure time set on the camera just has to be long enough for the action to happen while the shutter is still open. To keep the shutter open, it has to be set on Bulb. Because the room is dark, the long exposure time will not have any effect on the final output (this is because no light enters the lens to hit the sensor / film) To actually get an "exposure", a flash is fired. The flash light duration will now become the actual exposure time. Since nobody has the kind of lightning quick reflexes it would take to push the shutter cable right when the event was occurring, there is a work-around for that too. Freezing fast motion (AKA High Speed Photography), can give some pretty special photographic effects. High Speed Photography is used in physics, health research, sports and also for creative purposes. Higher speed flashes (shorter flash duration) will give Fig. 1.2 and 1.3 shows Laser Trigger MD1606, which costs – +/-R11 000
you a better result. If you have a slower flash cranked up to high power, the flash duration time will be slower. On the contrary, if you have a faster flash
cranked to a lower output (say 1/16 power), you'll have a faster pop- exactly what you need to have those strobes pop for a really short interval. That gives you the best result. Of course you still have to manage a great exposure, which is why digital cameras are awesome. You can just fire the camera a bunch of times and dial in your exposure. Two Profoto 7A packs, each with their own head and set on a low output, to create a very
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fast flash of 1/8000 of a second which is ideal. Similar results can be achieved with all kinds of lights, but attention must be paid to the specs. The Laser Trigger MD1606 (Fig 1.2. and 1.3.) is designed for high speed photographic beam triggering applications. The Laser system is comprised of three components, the Laser, Receiver and Control Module. Easy setup and alignment even on location in bright light are key to the ease of operation. Combined with the Electronic Cable Release, open flash technique is a thing of the past thus opening up a whole new world of high-speed photographic applications. Connect the Laser and Receiver to their respective ports on the Control Module and place the switch to the SET mode. A yellow setup LED will light indicating the output is inhibited. Align the Laser and Receiver keeping them on the same plane both vertically and horizontally. The green alignment verification LED located on the Laser Receiver lights when proper alignment has been established. After alignment, place the switch to the ON mode. In the ON mode the system will trigger each time the beam is broken and the Laser will turn off for two seconds. After each exposure the system automatically resets and at anytime the switch may be placed back into the SET mode to inhibit accidental triggering. A safety attenuator is located at the aperture of the Laser Module. The “SET” mode can be used as a standby mode between events. It’s easier to aim the laser across the targeted tripping point and then move the receiver into the path of the laser beam. The Laser works well even refracted through glass or liquids and can be used in bright ambient light. The smaller aperture UNIBLITZ shutters are generally referred to as High Speed Shutters. These devices tend to be utilized when fast exposures are necessary, i.e. when controlling a laser. All UNIBILTZ shutters can be considered High Speed shutters due to the speeds they can achieve relative to the size of the aperture. However, we also provide smaller apertures whose speed specifications are greater. These devices are the LS and the UHS series. The LS is a standard series and available on-line in 2mm (LS2), 3mm (LS3) and 6mm (LS6) apertures. The UHS1 (1mm
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aperture) is an ultra-high speed device that can provide pulses in the microsecond range.
For my practical exercise, I am going to photograph and object falling into a liquid … As shown in fig 1.3 and 1.4.
Fig. 1.3 and 1.4 show water as the main subject in these high speed photographs
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Reference List
http://www.uniblitz.com/capabilities.aspx
http://www.digitalpicturezone.com/digital-pictures/high-speed-photography-23-amazingpictures/ http://www.diyphotography.net/diy_high_speed_photography_at_home http://www.diyphotography.net/great-high-speed-photography-trigger-by-tom-barnett http://blog.chasejarvis.com/blog/2008/10/chase-jarvis-tech-high-speed.html http://www.kapturegroup.com/kap_htmls/laser.html
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