South African photographer Paul Godard and Festo are prototyping a dolly cart to automate time-lapse photographic sequences that incorporate a dynamic vantage point.
The project involves the development and construction of a highly precise automated dolly cart.
“Time lapse photography allows us to view the splendour of everyday occurrences which generally pass unnoticed,” says Greg Perks, Festo branch manager, Cape Town. “The theory behind the practice of time lapse photography is fairly simple to explain. All that is required is a camera which shoots multiple exposures over predefined time intervals. The images are then put together in post production to form the individual frames of a film sequence. By playing the images back faster than they were initially recorded an illusion of the rapid passage of time is created.”
What makes Paul Godard’s photography both challenging and extraordinary is the inclusion of a dynamic vantage point.
The implementation of this concept requires a precise rig from which to shoot because the camera needs to move on the horizontal plane and also rotate to achieve the result. Each rotary step between shots is required to move in a non-linear fashion, to maintain the camera’s focal point.
Tarren Smith, a Festo applications and project engineer, designed a computer program to provide quantifiable values for each angle on each horizontal step. Every scene requires a different set of rotary and linear axes values, since these depend on the focal distance.
The prototype comprises a dolly cart, built from 6 mm aluminium plates, and a series of 3,3 m long double rail tracks, which are joined together to form a track length of 30 m. Festo MTR-DCI intelligent servo motors provide the linear and rotary movements and a Festo FEC-FC30 PLC controls the axes movements. The PLC is also responsible for triggering both the focus and the shutter release of the camera. A Nikon D2X digital SLR camera is attached to the rotary plate using a standard video tripod head.
The MTR-DCI servo motor has an integrated motor controller which includes an absolute encoder providing precise positioning. The motor on the rotational axis has been matched to a gear with a 10:1 ratio. This makes possible movements of fractions of a degree – so small that they cannot be seen with the naked eye. The smallest movement that is programmable on this rig is 0,01°, which equates to 0,1° of motor rotation.
Smith explains the encoder selection, “Without an absolute encoder, errors in process steps become cumulative. As a result, minor errors in the process steps would throw the entire shot sequence off focal point, within a fairly small number of process steps.
“This project has proved to be incredibly rewarding. The initial results are extremely encouraging – we have managed to capture very impressive scenes that incorporate a dynamic vantage point.”
For more information contact Joanne Dexter, Festo, +27 (0)11 971 5560, [email protected], www.festo.com
| Tel: | 08600 FESTO (33786) |
| Fax: | +27 11 974 2157 |
| Email: | [email protected] |
| www: | www.festo.co.za |
| Articles: | More information and articles about Festo |
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