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Cinematography page 7

 
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.

What is color temperature? Color temperature is important to the cinematographer for a number of reasons. Technically it is vital that any light source that is to appear neutral in the final rendition of the scene is emitting light of the same color balance as that for which the film has been designed. Artistically it is important that the cinematographer has an understanding of the psychological and emotional effects of the color of light within a scene and that they have complete control over this color.

Filters are used to alter the image either for technical reasons to correct the color of the light to that required by the film being used, or because the cinematographer may wish to change the image in some way that will enhance their story-telling powers.
In order to change the color (and therefore the color temperature) of a light source we usually put a filter in its path. A blue filter will cause the light passing through it to appear more blue but it will also reduce the intensity, or amount of energy, of the light. This is because filters do not add color but actually absorb or subtract color. 

A blue filter will therefore be absorbing the wavelengths of red light in order to make the subsequent light appear more blue. It does this by converting the light absorbed into heat that has a direct relationship to light, both being a vibrational energy. It is important to remember this for it is one reason why gelatin filters on lamps first bleach out and eventually burn through.

Filters are used in cinematography to alter the image either for technical reasons to correct the color of the light to that required by the film we are using, or because the cinematographer may wish to change the image in some way that will enhance their story-telling powers. The former is often necessary, the latter much more fun. Effects filters are usually described by some term that indicates what will change they will make to the image, for example fog filter.


Color compensating filters have only a limited use in cinematography, as they are primarily available for fine-tuning colors in transparency or reversal work. They do come into their own, however, when a cinematographer has to work with this available light from fluorescent tubes, which often have an excess of green light. This discrepancy can be corrected by putting the appropriate magenta filter, magenta (as previously mentioned) being the complementary color to green, over the tubes or in front of the lens of no other source of light is to be added.

Color temperature meters come in two basic forms, reading either two or three colors. The two-color meter reads only blue and red. It is not sophisticated enough for a working cinematographer but is useful for setting filters on lamps as this usually only concerns blue and red. For the professional cinematographer the three-color meter is essential as it adds a reading in green. A three-color meter is required if readings are to be made from fluorescent tubes, mercury vapor lamps, etc. 

For the cinematographer wishing to convincingly re-create daylight it is important to understand that the different sources (direct sun, shadow and deep shadow) will all have different color temperatures. There are a number of reasons why this is the case. Direct sunlight varies, mainly, due to the amount of cloud in the sky. In the morning and afternoon it is taking the much shorter path directly from above. This, together with dramatically varying amounts of water suspended in the air, will clearly change the color of the light passing through the atmosphere. In the shadowed area matters are different. 

 
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