When there is a shallow depth of field, an image feels sharper than when there is a wide DOF. I think this is because of the contrast between the in-focus elements and the background. The circle of confusion at in-focus points should be the same since zs=zi. I find this interesting since sharpness in an image is therefore more about contrast of focus in the image rather than how focused the photons are at the sensor.
When there is a shallow depth of field, an image feels sharper than when there is a wide DOF. I think this is because of the contrast between the in-focus elements and the background. The circle of confusion at in-focus points should be the same since zs=zi. I find this interesting since sharpness in an image is therefore more about contrast of focus in the image rather than how focused the photons are at the sensor.