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Geomaterials (i.e., rock, sand, soil and concrete) are increasingly being encountered and used in extreme environments, in terms of the pressure magnitude and the loading rate. Advancing the understanding of the mechanical response of materials to impact loading relies heavily on having suitable high-speed diagnostics. One such diagnostic is high-speed photography, which combined with a variety of digital optical measurement techniques can provide detailed insights into phenomena including fracture, impact, fragmentation and penetration in geological materials. This review begins with a brief history of high-speed imaging. Section 2 discusses of the current state-of-the-art of high-speed cameras, which includes a comparison between Charge-Coupled Device (CCD) and Complementary Metal-Oxide-Semiconductor (CMOS) sensors. The application of high-speed photography to geomechanical experiments is summarized in Section 3. Section 4 is concerned with digital optical measurement techniques including photoelastic coating, Moiré, caustics, holographic interferometry (HI), particle image velocimetry (PIV), digital image correlation (DIC) and infrared thermography (IRT), in combination with highspeed photography to capture transient phenomena. The last section provides a brief summary and discussion of future directions in the field.

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