Depth of focus refers to the tolerance of the film, sensor, or printing paper placement around the exact focus point while still producing an image that appears acceptably sharp. Unlike depth of field, which relates to the subject side of the lens, depth of focus concerns the image plane side-how much leeway there is in positioning the medium without losing sharpness. Understanding depth of focus is important in macro photography, large-format cameras, and printing processes, where precise alignment is critical for achieving high-quality, sharply focused results.