Second, the light is even. Many people use mobile phones or SLR to shoot a work, which is often half bright and half dark. The reason is that there is a problem with running out of light or improper use of flash. If the computer post-processing highlights the dark part at the bottom of the work, the overall effect of the work will be distorted.
Third, it is still distortion. Calligraphy works, no matter how many feet, are horizontal and vertical squares. If the lens is not perpendicular to the paper and the four corners are not parallel when shooting, the handwriting of the work will be somewhat distorted (which any calligrapher can't tolerate).