Regarding this slide and the next few slides, note that the focal length does not inherently introduce distortion into photos (excluding the 15mm fisheye photo on this slide from lenses that purposefully distort or have bad optical design). For example, there's a misconception that you shouldn't take portraits of people's faces with wide angle (small focal length) lenses because it distorts their facial features. However, the distortion that you'd probably see comes from perspective distortion from simply being too close to the subject's face. If you crop a photo taken with a wide angle lens to the same field of view as one taken with a higher focal length lens, they will look the same besides differences in resolution from cropping. https://photographylife.com/does-focal-length-distort-subjects
Regarding this slide and the next few slides, note that the focal length does not inherently introduce distortion into photos (excluding the 15mm fisheye photo on this slide from lenses that purposefully distort or have bad optical design). For example, there's a misconception that you shouldn't take portraits of people's faces with wide angle (small focal length) lenses because it distorts their facial features. However, the distortion that you'd probably see comes from perspective distortion from simply being too close to the subject's face. If you crop a photo taken with a wide angle lens to the same field of view as one taken with a higher focal length lens, they will look the same besides differences in resolution from cropping. https://photographylife.com/does-focal-length-distort-subjects