This is mainly a post-processing effect, not just shallow depth of field. Based on the answers, the usual ways to get it are:

• apply strong noise reduction for an overall softened look
• use Photoshop blur tools such as Surface Blur or Lens Blur
• apply the effect only to selected areas like hair and skin using a layer mask

Surface Blur is often a good fit because it smooths similar tones while preserving stronger edges better than a normal blur. Radius controls how much blur you get; Threshold controls how similar tones must be before they blend. Higher threshold acts more like regular blur, while lower values keep edges sharper.

A practical workflow is:

1. Duplicate the image layer.
2. Apply Surface Blur or Lens Blur to the duplicate.
3. Add a layer mask and reveal the effect only on hair/skin.
4. Leave eyes, lips, and other detail areas sharper.
5. If the result looks too artificial, add a little monochromatic Gaussian noise to restore a more natural texture.

Global noise reduction can also work, but it may soften important facial details too much.