Depth of field

Depth of field is often discussed in technical ways, and new photographers might not understand what it means in terms of image sharpness as actually perceived by the eye. I thought the image below was illustrative. I shows how the plane of image sharpness cuts like a razor through the subject—sharp detail exists only in a 3-4mm-deep plane (at most). This is why focusing accuracy is critical for many types of work.

Depth of field—Canon EF 105mm f/2.8 @ f/4
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