Photography optics, fans come in.

1 Just as Chinese cabbage kernels are more delicious than Chinese cabbage ribs, zoom lenses generally have a better telephoto segment than a wide-angle segment, and the center is better than the periphery. There is something wrong with the process.

Considering the best aperture of the lens, a F2.8 head is basically useless, and the best aperture of most lenses is around 8.

3 don't understand