Depth of fieldIn optics, particularly as it relates to film and photography, the depth of field (DOF) is the portion of a scene that appears sharp in the image. Although a lens can precisely focus at only one distance, the decrease in sharpness is gradual on either side of the focused distance, so that within the DOF, the unsharpness is imperceptible under normal viewing conditions.
A macro photograph with very shallow depth of field.
At f/32, the background is distracting.
At f/5.6, the flowers are isolated from the background.
A memory card reader is a device used for communication with a smart card or a flash memory card
A USB Card Reader like this one, will typically implement the USB mass storage device class.
A PC having a cardreader instead of floppy disk drive.