Generally film emulsion in holography runs about 10 microns thick. That's pretty small, but a photon measures about a half of a single micron in size. That's smaller than an ants asshole. So the emulsion seems pretty large to a photon. That's how we are able to photograph this microscopic wave impression in film and make holograms.
Holograms are photographs of the three dimensional impressions stored on light waves.
Sort of like fossils. When you pour plaster into a fossil, let it harden, and then remove it, you have a three dimensional sculpture of the impression that was left in the stone. Similarly, when you pour jello into a jello mold, let it set, and then remove it, you have a three dimensional sculpture of the shape of the jello mold. And when you put light into a hologram, you get a three dimensional sculpture in light of the object that left its impressions on a photon and was captured within the thickness of a photographic emulsion. Of course, there is a trick to this.