The size of wind turbine blades is expected to increase considerably in the future. Since the modern wind turbine blade is generally large-scale, faulty design production results in high expense. To achieve a desired wind turbine blade, a better understanding of the structural behavior on different scale is necessary. Although the structural deformation of the full-scale blade under various loads is an important parameter in the analysis of structural behavior and the blade's performance, there are many difficulties in an accurate deformation measurement of the large-scale wind turbine blade. A videometric technique reported here was developed to determine the large-scale blade deformations. The technique principle and methodology will be presented in the current paper, which involves the detail of implementation in the large-scale blade deformation measurement. Some application examples with the obtained data and their analysis are presented, which demonstrates the technique's application on large-scale wind turbine blade, and which is relevant to understanding the structural behavior of wind turbine blade in the full-scale tests and during operation. The videometric technique will be useful for structural investigation of composite wind turbine blades. A wide variety of other applications, especially those involving fieldwork, could exploit this implementation of videometric. (c) 2012 Elsevier Ltd. All rights reserved.