## 1 Introduction  
In order to identify the modal parameters of a structure it is necessary to deal with measurements such as acceleration, velocity, or displacement signals. These temporal signals can be processed, using the continuous wavelet transform for example, to determine the natural frequency, the damping ratio, and the mode shape for each mode. Nowadays, the current metrology tools for vibration measurement are mainly based on the use of accelerometers and laser vibrometers [1, 2]. However, in order to obtain a sufficiently precise description of the mode shapes of a studied structure, a large number of sensors have to be installed. Depending on the size of the structure, the use of accelerometers can introduce additional damping due to the connecting cables, but also additional masses due to the sensors themselves [3]. The laser vibrometers require surfaces whose direction of reflection remains relatively unchanged during the test and free from edge effects. These conditions are difficult to guarantee in certain cases. In order to carry out field measurements (speed or displacement), scanning vibrometers also require the use of a periodic stationary excitation, which is a limitation. For the past decade, digital image correlation (DIC) has been increasingly used in the mechanics of materials and structures to determine, in particular, 2D and 3D strain fields. Indeed, when the experimental conditions are optimal, it is possible to obtain a displacement resolution of less than one tenth or even one hundredth of a pixel [4]. This technique can be applied for the analysis of dynamic loads with the use of high-speed cameras. However, the latter are often limited in terms of image definition, which restricts the spatial resolution of the analysis and penalizes the analysis of slender structures such as those encountered in civil engineering. New generations of cameras, presenting a wide variety of combinations of image definition and acquisition frequency, make it possible to push back these limits and thus constitute potential alternatives to the conventional modal analysis instrumentation. In the literature, some studies have explored the use of fast imaging techniques to perform modal analysis of structural elements [5; 6]. [PERSON] et al. [7] have studied the influence of the speckle to identify the best suited for the monitoring of random vibration. Although there is a correlation between the size of the spots and the size of the patterns, this study does not take into account the size of the patterns used for the DIC, which are always 15 px\({}^{2}\). The different results obtained are compared with those inferred from strain gauges and laser vibrometer measurements. Although the application of imaging techniques in dynamic experiments is in constant progress, the studies of some authors, as in [8], are limited by the frame rate of the camera. Cameras with on-board memory (such as the Photron SA series) can reach higher frame rates, but their image definition is limited (typically 1 or 2 megapixels) and the test duration is then restricted by the available memory (a few seconds). Recent alternative camera technologies, associated with very high-speed data transfer solutions, permit us to record several thousand images per second at relatively high resolutions and during rather long sequences (e.g., 12 megapixels at 190 Hz for the JAI SP-12000M-CXP4, which can also be used at much higher frame rates on smaller images). More details will be given in the next part. The use of such a camera makes it possible to obtain a quasi-continuous measurement of the studied object. However, few tools have been developed to analyze this amount of information and most authors compare the displacement fields and the modal deformations obtained with the results of finite element (FE) calculations [9; 10]. Some researchers caution about the frequency of cameras' fans, which can disturb the measurements [11; 12]. In order to obtain the displacements using fast imaging, [PERSON] et al.