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The first step in the creation of a time-lapse video is to select a subject. Until a subject has been identified and observed in some detail it is difficult to set the basic parameters for the project.

A key consideration is the rate of movement of the subject because this determines the intervals at which single frames should be captured. A subject such as a plant growing, or a flower opening, might need to be photographed at intervals of 30 minutes or one hour over a period of days, but clouds moving across the sky would typically be photographed at much shorter intervals - perhaps every 10 seconds over a period of 30 or 45 minutes.

Another parameter that must be set prior to beginning the photography is how long the video should last and at what frame rate it should be presented. Television channels are broadcast at anything between about 24 frames per second and 60 frames per second, and traditional film-based movies were sometimes projected as slowly as 16 or 18 frames per second. Lower frame rates generally produce a rather more jumpy and disjointed flow of movement. A faster frame rate gives a smoother presentation.

Remember that frame rate is not just about the smoothness of movement in the final video. It also has a big effect on the number of images that must be taken. For a ten-second video presented at 30 frames per second it is necessary to take a total of 10 x 30 = 300 images. For the same ten second video presented at 18 frames per second, a total of 10 x 18 = 180 frames are required.

If 18 frames per second is considered an adequate frame rate, and the event to be photographed takes place over 12 hours, then the 180 frames required for a ten-second video must be taken at intervals of 12 hours divided by 180 - ie 4 minutes.

Having set the key parameters, set up a digital camera on a very stable tripod and attach and program an intervalometer. Set the appropriate interval at which images should be taken and the total number of images to be exposed. Some devices also allow the user to program the times at which the interval timer should start and finish. Professional cameras, such as the Nikon D3 and D4, have these facilities built in so no additional equipment is required.

In some cases, provision may have to be made to light the subject, perhaps using flash. This removes the variations in outdoor light intensity on small subjects caused by the Sun being covered by clouds etc. In the case of an event that lasts longer than one day, it is obviously necessary to light the subject if photography is to continue throughout the night.

Once the pictures have all been taken, they should be resized to match the dimensions of the video and saved in the appropriate format - usually JPEG. They are then imported into time-lapse video software such as Windows Movie Maker or VideoVelocity 3. Sound can then be added as required before the video is output and saved in the chosen format. Note that Windows Movie Maker cannot output videos with a frame rate greater than 8 frames per second.


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