Top Coat Adhesive Emulsion (Silver Halides) Support Material (Plastic) Adhesive Backing Film Cross-section

Silver-Halide Crystals The emulsion consists of gelatin containing light sensitive silver halide crystals such as silver bromide and silver chloride. The light sensitive crystals change shape when exposed to light, which are then converted to a dark metallic silver, giving us the image that we see.

Microscope image of crystals

Zooming in on grain

ISO and film grain A film with a low ISO number has a finer grain in the film. The result: 1. It is less sensitive to light (A film with an ISO of 200 is twice as sensitive to light as a film with an ISO of 100. ) 2. You are able to get finer detail when making enlargements

Low Film Speed

High Film Speed

Photo Paper two types of paper: Fibre Based and Resin Coated (RC) paper can also be Graded for contrast: Graded Paper vs. Multi-Grade we use Ilford RC Multi-Grade Paper

Paper Cross-section Top Coat Emulsion Resin Backing

Why can we walk around with photo paper in the darkroom? Safelights: All safelights work on the same principle. They eliminate the wavelengths of light that B&W photographic paper is sensitive to and produce a light that will not expose or "fog" the paper while you are working. Most safelights use a filter and an incandescent lamp to achieve this goal.