Lighting ratios are another concept cinematographers must adapt to. It is important before lighting a scene to be able to visualize the lighting ratio they are going to use. A lighting ratio is the figure given to a measured relative difference in brightness two parts of a scene. It is very time-consuming to have to change the light ratios after it was thought that the lighting on the set was finished. The way films are funded these days, with often a significant amount of the production’s capitalization coming up front from television rights and video sell-throughs, it is important that the cinematographer knows when shooting a scene exactly how it will look when delivered on the two, quite different, media. The key to this is the lighting ratio. The first thing to realize is that the tonal range of the television version is going to have to come from within the tonal range of the cinema version.

The most common use of light ratios is in the control of how the human face is lit. If the cinematographer successfully lights a face and is looking for the simplest way of noting their success, the easiest thing to do is to record, or simply remember, the lighting ratio.

One way to keep track of you notes, like cinematographer Daryn Okada does, is to use a powerbook. “How did I get hooked on this method? I got into using a powerbook because I hated having to write my notes again and again. At each script revision and schedule came in, I had to find a better way to manage and keep track of photographic details with visual references and the means to accomplish them.

At first, I made a lot of lists. Lists of visual ideas relating to the story, if camera movement, lighting, equipment, etc. I’m always writing some idea on some piece of paper. Soon, I began copying them into a notebook but thought it would be great to be able to always refer to the script and schedule, except as we all know, those elements keep changing during the pre-production process. So, I began to try programs and compartmentalize everything.”

If the idea was to light a rather light piece with say, a leading lady aged perhaps late forties but playing a part written as thirty or so, a lighting ratio of 2:1 would be very flattering. This is because with the brighter side of the face only twice the brightness of the darker side the shadows in the smile lines by her eyes would only be half the brightness of the lit side of the face.

In order to establish the correct aperture to set on the lens, take a reading (using a spot meter) on the most important subject in the scene.

As there would be little difference in brightness between the smooth skin and the lined skin the lines would hardly show- all very flattering. If, on the other hand they were lighting a more dramatic piece, say a thriller, then they might let the lighting ratio on the leading man rise to 8:1 or three stops difference. The night scenes for the same film might rise to 16:1, but this is very dramatic- the detail in the shadowed side of the face is going to start to disappear soon and will almost certainly show as black on television.In order to establish the correct aperture to set on the lens, take a reading (using a spot meter) on the most important subject in the scene. As this will usually be the main character in the scene, their lit skin tone is generally used. If they are Caucasian then the reading on the spot meter used will be one stop over the setting for an 18 percent gray card.

The only other caveat is that all the readings for this technique must be taken from in front of or very near to the lens, for only then will the reflectance of all the surfaces in the scene be the same for the spot meter as for the film. The second most important part of filming a scene (to cinematographers) is the shadows, and measuring these correctly is crucial.

If the cinematographer finds that there is an important part of the scene which has read a little above the maximum white but wishes to photograph it, one relatively simple solution is to light the subject’s face a little brighter. This will enable them to stop down enough to bring the highlight within the recordable tonal range.

After doing this, they will need to recheck the shadows to make sure none of them have now fallen outside the film’s tonal range. More simply, if there are some shadows that fall below the recordable tonal range then simply adding a little more fill light will bring them up to a recordable level. On an exterior this might simply be done with a reflector.