Depth of field

What the numbers mean

The line under the side view is the depth of field for the picture above. Distance is how far the camera stands from the subject. Near and far are the closest and farthest points that still count as sharp. Hyperfocal is the focus distance that keeps everything from half that distance out to infinity acceptable.

This page opens at 85mm and f/1.8 on a full-frame sensor, in the face framing of the portrait. Move focal length, aperture or sensor and the numbers follow. The same formula draws the green focus band in the side view.

What changes the sharp zone

A lower f-number makes the zone thinner. A longer lens, focused closer for the same head size, also makes it thinner. A larger sensor, at the same framing, blurs the background more because the lens is longer or the aperture is effectively wider. The simulator uses a circle of confusion of one pixel on an 800-pixel-wide frame, the same limit as the side view.

Questions

What is depth of field?

The range of distances that still look sharp at the chosen focus. In front of the near limit and behind the far limit, the picture is out of focus.

Which circle of confusion is used?

One pixel on an 800-pixel-wide frame. On full frame that is 36 mm divided by 800, about 0.045 mm. The hyperfocal distance is f² / (N c) + f.

Does the sensor change depth of field?

Yes, once the framing stays the same. A smaller sensor needs a shorter lens for the same head size, and that shorter lens keeps more of the background sharp at the same f-number.