Monday, June 30, 2014

Time-lapse, a Window of Opportunity



There is a question of what the term time-lapse means exactly, when referenced to photography and or imaging. According to the website Webopedia, the definition of time-lapse is: “In digital photography, it's the name of the process used to capture a set of images at preset intervals of time.” This seems to be a reasonable definition for either digital or analog image capture, which can go further as the preset intervals of time can be also termed as the frame rate of image capture.


To explain this, a frame is a single image or photo and the frame rate is how quickly these frames are acquired or taken. The frame rate of time-lapse photography can then be very diverse, to in effect any quantity, from the normal frame rates used to fool our eyes for motion pictures, between 24 to 30 frames per second, to frame rates of only one frame per second, minute, day, or even a week or more, depending on the slowness of the process being imaged in a sequence. This method can be called “slow process” time-lapse imaging.

The term "time-lapse" can also apply to how long the shutter of a camera is open during the exposure for the image. A great example of this type of “time-lapse” imaging is the Hubble Space Telescope’s Deep Field image, which uncovered a perplexing collection of at least 1,500 galaxies in an assortment of stages of evolution. In this instance, a long shutter opening, or long preset interval of time, was necessary to allow the dim light of the galaxies to register on Hubble’s imaging chips.

hubbledeepfield
Hubble Space Telescope Deep Field Detail

Using the above definitions of time-lapse, we now know that time-lapse is a process to capture a set, or sequence, of images, or better, data, at preset intervals of time, and that time-lapse also represents the preset lapsed time that a shutter is open to expose the imaging medium, or in the instance of data, how long the data is read. What is important here is the preset intervals of time and for how long these intervals of time are set as data is collected.

On the other side of the “slow process” time-lapse imaging spectrum, is imaging at frame rates which are much faster than the eye fooling 24 to 30 frames per second for “fast process” imaging. This is typically called high frame rate capture. Here, intervals of time as high as 100,000 frames per second are used to capture images or data. These time-lapse images, when played back at the normal eye fooling 24 to 30 frames per second, show the fast process as virtually slowed down. There are many examples of fast process imaging on the net, for example the detail exposed of a water balloon exploding when hit with a sharp object.

water balloon slow motion
Water Balloon Exploding Slow Motion

I was introduced to time-lapse in the late 1980’s, when I joined a small start-up company that specialized in arc welding and high temperature process imaging. The imaging system that we developed could see through the very bright light of an arc welding process. With this system one could clearly see the welding pool, the cathodic cleaning at the edge of the pool, and the corrosion of the electrode during the weld. This system used a high-speed charged couple device (CCD) camera, a specialized image intensifier tube, spectrum filtering, and an ultraviolet pulsed laser as the light source. The camera system had a shutter speed that went as fast as 10-nanoseconds, or 10 billionths of a second, and the pulsed laser which provided illumination to the subject matter for a mere 5-nanoseconds.

This system used the very essence of the term “time-lapse”, due to the natural delay between the electronic triggering of the laser and actually receiving a pulse of laser light. This necessitated a precise interval of time between the shutter’s opening and laser light pulse, hence, the imagery was acquired at preset intervals of time, or in a "time-lapse" fashion. This imaging system’s timing exactness introduced me to time-lapse not only in videography, but also in electronic timing and data collection, and I have been working with time-lapse based systems ever since.

My company offers several time-lapse imaging suite applications that I wrote for both slow processes and fast. One application that is offered is for Windows based systems and another, called Controlled Capture, is for Android phones and tablets. If you would like to experiment with time-lapse imaging, I invite you to give them a try as we offer them for free. You can find these applications at Controlled Capture Systems or on Google Play. Time-lapse is not only for digital imaging in photography or videography, but time-lapse is also for electronic data sampling, for sensing and detection, and for precise data collection during a preset time interval, or window of opportunity.

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