補充一下,說明書其實說的很清楚,景深預覽鍵的動作,機身鏡頭會做什麼,要從哪裡看,一清二楚 Page85 of EOS 350D manual: Depth of field preview Press the depth-of-field preview button to stop down to the current aperture setting. The diaphragm is the lens will close to the current aperture and you can check the dipth of field(range of acceptable focus) through the viewfinder.