The inch of a photo refers to the inch value of the long side of the photo;

1 inch =2.54 cm; 30 inches =60.96 cm; 40 inches = 10 1.6 cm

Size difference: the length of the 30-inch photo is 25.4cm× 20.32cm smaller than that of the 40-inch photo.

Extended data

Application of correlation dimension

ID card, physical examination form, etc. Most of them are 22×32mm small, 26mm×32mm second-generation ID cards, and 25mm×35mm ordinary one-inch photos. The standard photo size of passports and travel documents is 48mm×33mm, the head width is 2 1 mm ~ 24 mm, and the head length is 28 mm ~ 33 mm). ?

References:

Baidu encyclopedia-photo size