A. SIFT and SURF are two popular feature extraction and matching algorithms used in computer vision and image processing. Here are some key differences between them: 1. Speed: SURF is generally faster than SIFT, especially in terms of feature detection, due to its simplified algorithm and implementation. 2. Robustness: SIFT is generally considered more robust than SURF, especially in the presence of image transformations such as rotation, scaling, and affine distortion. 3. Descriptor size: SURF has a smaller descriptor size than SIFT, which can be an advantage in certain applications where memory or processing power is limited. 4. Scale-space extrema detection: SIFT uses the Difference of Gaussian (DoG) as a scale-space extrema detector, while SURF uses the Hessian matrix determinant. 5. Patented: SIFT is a patented algorithm, which means that its use is restricted in some contexts. In contrast, SURF is not patented and can be used freely.