FEATURES - Cinematography

Cinematography page 3

By 1926 the American Society of Motion Picture Engineers (SMPT later the SMPTE) Standards and Nomenclature Committee recommended camera cranking speeds as follows: Regarding camera speed we recommend practice: a camera cranking speed of sixty feet per minute (16fps), with a minimum of fifty-five feet and a maximum of sixty-five feet when normal action is desired, in connection with the Society of Motion Picture Engineers recommended practice of eighty feet per minute projection speed (21 fps).

The result of this is that from the turn of the century to the coming of sound the camera frame rate was set at roughly sixteen frames per second. When sound recorded optically on the same film as the picture came in around 1927 the frame rate of 16 fps or 60 feet of film per minute was too slow to make an adequate sound recording using the optical recording techniques available at the time. A faster speed was needed to enable more frequencies to be recorded. 

By now it was known that the flicker apparent in a film projection rate of 20 fps. At 30 fps it appeared to disappear completely, even on the most demanding scenes- these usually being those with pronounced highlights as flicker is more discernible in the brighter areas of a scene. 

American cinematographers therefore chose the very convenient frame rate of 24 fps as being almost totally free of any flicker, producing a linear film speed sufficiently high to enable good sound to be recorded next to the picture on the same piece of film. This enabled the projectors to drive at a constant speed from a simple synchronous motor. 24 fps is today the world standard frame rate for theatrical motion pictures.

Lenses: When you come to order a lens set for a picture, you are faced with a number of interesting problems and choices. These relate to: Definition or sharpness. Speed or maximum aperture Contrast, or how quickly does black become white? Do you need prime lenses, a zoom or both?
What focal lengths do you need? Should you include extreme wide angle or telephoto?

Lenses have developed dramatically over the last twenty years. During this time there have been two areas where lens designers have concentrated their efforts- speed and definition.

It is common, especially on feature films these days, to shoot with some kind of diffusion filter on the lens. You must be very careful and aware when you chose your lens set. Some lenses that appear to have high specification may not perform as well as others depending on the way you are going to use them. The character of the lens, under the circumstances you are going to use it, often means more to the cinematographer than the other member of the crew. 

Most importantly, remember that your audience has come to be entertained and will probably never know what lens you used, nor will they care- all they are interested in is that you stir their emotions. Audiences become wrapped up in story line, acting ability, colors and images. The technicalities of how the picture was developed are not of high interest to most viewers.  So which range of lenses should you choose? 

There are several kinds that are all superb, including Ziess, Primos and Cooke S4s. What is important is that you read the script first, decide on the look you want and then choose the lens set that suits you best. Today's cinematographers are extraordinary lucky to have several different sets of lenses to choose from. After lenses are chosen, what can be done with them is a whole other story. Lenses are used for such things as distortion and aberration of images along with color enhancement.

The three most common forms of optical distortion that occur in lenses are known as pincushion distortion, barreling and chromatic aberration. Prime lenses very rarely show any discernible distortion. The exception might be extreme wide-angle lenses, some of which show a slight tendency to barrel. The finest zoom lenses will show no discernible distortion even at the widest end of their range. 

The most common or exaggerated distortion is barreling at the wider end of the zoom. The manufacturers do their best but, as in all things, you get what you pay for and if you are asking for two of the lenses' attributes to be long zoom range and wide aperture then almost certainly other parameters of the design will suffer. 

In this case the choice usually tends towards a design where a noticeable amount of barreling occurs at the wide end and very noticeable image size change shows strongly when the focus is changed. These are all considerations a cinematographer must take into account before filming begins. If the cinematographer finds that in the middle of a shoot a different camera or lens will be needed that is not readily available, production could be drastically slowed or even halted.

Today's color film stocks are somewhat complicated items consisting of a support medium, known as the base. This is coated on one side with as many as nine layers of light-sensitive coating. In addition there are several other layers such as the yellow filter layer. All of these layers are collectively known as the emulsion. 

The top layer of the emulsion is known as the super coat, whose purpose is both to protect the film from mechanical damage and to lubricate it through the camera gate. On the reverse side of the base, there is a removable coating called the ram-jet layer. This is black and eliminates halation- haloes around bright points of light. It is anti-static and also lubricated. Considering film consists of so man layers, it is amazing that it is so thin.

The history of negative/positive photographic process: The knowledge of photosensitive salts was noted by Albertus Magnus as long ago as the thirteenth century. Although this is the case, the bases of obtaining an image using these salts was worked upon but not made practical in the sense we know photography today until the mid-nineteenth century. 

In 1819 Sir John Hershel, a British scientist, discovered sodium hyposulphate and its ability to dissolve silver chloride. Then in 1839 (twenty years later) he told William Henry Fox Talbot of the discovery. By this time Fox Talbot had developed a method of obtaining an image on photosensitive paper using a silver halide as the reactive chemical. 

The image was a negative one, but he had not found a method of making it permanent, or fixing it. Putting these processes together, it was found that Sodium hyposulphate dissolved out the still sensitive silver halide crystals leaving stable metallic silver as the image. 

It was not until January 31st, 1839 that Fox Talbot was able to present a paper to the royal society in London showing he could make 'Photogenic Drawings' or shadows of real objects. By the end of September 1840 Fox Talbot had discovered the theory of the latent image and found a method of developing it and stabilizing, or fixing it, to an acceptable degree of permanence using Hershal's sodium hydrosulphate. This technique he called the photographic process. At this stage, though, both the negative and the positive had to be made on paper soaked in the light-sensitive solution.