Depth of field stands for the range that is sharp on a photograph. The bigger the diafragma (camera opening) the smaller the range that will be sharp on the picture. A bigger diafragma also means a shorter shutter opening (so the picture doesn't become too bright). I'm interested in the physical explanation of this effect. The explanation on wikipedia is much too technical for me to follow. I am not a physicist I just enjoy reading about it, so please explain as if to someone who has no idea about the field, thanks.