Using light fields, we are able to focus pictures after they are taken. We do so by aligning our picture with respect to content at the desired scene depth and then averaging all of the sub-aperture images (i.e. our light field data). Sub-aperture averages are equivalent in principle to holistic full-aperture photographs.
We can also adjust the aperture size – i.e. the depth of field in a practical sense – by including more or less sub-aperture images in our average. A greater amount of images translates to a larger aperture (…because more images, more light!).