Sean Crowley on Lens Field Curvature and Soft Corners

Many camera and lens reviews comment about how some lenses are “sharp in the center but the corners are soft.” Well, as Sean Crowley explains so clearly in his video, it’s not necessarily that lenses are not sharp at the corners, it’s just that the corners are out of focus. Some quality lenses allow you to shift the focus from the center to the corners, allowing sharp out-of-center subjects. But, can’t you do that by just prefocusing using the center of the lens, lock focus and then adjusting composition so that the subject is now at the side? For the answer, you’ve got to watch the video — and I encourage you all to follow his YouTube channel (so we can have more goodies in the series).