Properties of wood samples in the mechanical pulping process can be studied using high strain rate loading tests. The mechanical properties are usually measured as a stress-strain relation. However, wood has an inhomogeneous structure and its properties are greatly affected by environmental factors. Because of the inhomogeneous structure of wood, the average strain over a large sample having several annual rings is not a satisfactory measurement. The local strain levels in the wood need to be defined. This thesis presents a measurement technique based on high speed image acquisition and correlation-based image analysis that allows the definition of the local strain levels in the sample during deformation. The main goal of the work was the implementation of a high speed image acquisition system and analysis algorithm as well as to complete the measurements. A representative number of samples are analysed to ensure the efficacy of the method and certain conclusions can be drawn concerning the behaviour of the wood. The thesis consists of three parts. The first part presents the measurements along with the test samples and the testing device. The high speed camera and camera optics that were used are also described. The choice of illumination method is discussed and finally there is an account of problems faced during the measurements. The second part of the thesis considers the image analysis algorithms. There is also a brief consideration of several alternative methods followed by an explanation of the basic principles of the Digital Image Correlation (DIC) algorithm. The second part concludes with an explanation of the algorithm used, which employs the same principles as DIC. The final section presents the calculated strain levels from the chosen samples. The high speed recording of the high strain rate loading process worked well and almost all the test cases were successfully recorded. The analysis of the test cases yielded positive results. The strain in the sample focussed on a few narrow regions. The wood in these regions underwent high deformation the while rest of the sample remained unaffected. In addition the fatigue level of the samples and test temperature was observed to have an effect on the strain levels in the sample. /Kir10