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The Kodak Film Professional’s
Guide to Motion Picture Film
Film Basics:
Eastman Kodak currently manufactures many different motion picture films. These products vary by "Film Code," that is, the emulsion type, and format; the width of the film. Lengths of camera films range from fifty to two thousand feet.
Camera film types include "Negative," which is the general choice among professional users, and "Reversal" film. Negative film cannot be projected after processing. It must be printed in the laboratory or be transferred to videotape on a "telecine" for television applications. Reversal films can be projected immediately after processing because they duplicate reversal film. Kodak manufacturers a whole series of materials for reversal film applications. More on this later.
Choosing a Film:
There are very definite reasons for selecting a Negative or a Reversal camera film. Special applications aside, a Reversal film is generally used when:
* There will be no need for more than one copy of the film.
* Time between photography and projection (or transfer) is critical (as in News).
* Economy. It is less expensive to shoot Reversal film and develop than to shoot negative and develop and print.
* Black and white Reversal films tend to be a bit sharper for their given speed than he Negative / Positive process.
Disadvantages of Reversal films include:
Negative films offer a wide selection of products and a choice of several different "looks." The concept behind the Kodak "Family or Films," especially in the VISION Series, is to provide a consistent "look" across a large range of film "speeds."
A quick review of film "Speed":
"Speed" is an old photographic term that relates to how quickly a photographic material reacts to light during exposure. This meaning dates from a time when exposures were measured in terms of minutes, not fractions of a second. The description of "Timing" a print has the same origin. In either case, we are not really discussing the movement of anything, but rather an amount of light striking the film. As in still photography, the volume of light that reaches the film is controlled in part by the camera’s "Shutter Speed" setting.
In a typical movie camera, the "Shutter Speed" is usually about half of the frame rate; that is, if the camera is running at the standard 24 frames per second, the shutter speed is about 1/50th of a second.
A typical shutter consists of a rotating disc in the path of the light with a "cutout opening" of almost 180 degrees. While the solid part of the shutter disc is covering the light path, the film is brought into place in the "film gate," where it will be exposed. Once this happens, the continuing rotation of the shutter brings the cutout area in front of the film gate, letting light strike the film. Once the cutout passes, the light is blocked, and the next frame of film is moved into place. This process is repeated 24 times per second under ordinary circumstances. Since the cutout is about half the disc area it is equal to about half the time, or 1/48 of a second. By making this cutout larger or smaller, the shutter speed can be varied. Unless the camera operator specifically changes this shutter speed (on cameras that have this ability), or changes the frame rate of the film, such as in "slow motion" cinematography, the 1/50th of a second stays the same.
As in still photography, the amount of light striking the film is also determined by the "F-Stop," or lens opening selected, and of course, the actual lighting condition.
The idea behind Kodak’s offering so many choices of Color Negative Film is to provide a film that is ideal for every lighting situation. Decades ago, when there was only a single type of Color Negative, the cinematographer faced with a low-light situation would have to have the laboratory "force develop" the film to increase its speed. This can be overheating the chemistry being used. This practice offers limited success and sometimes-unpredictable results. Force-develop film tends to have increased contrast and graininess, degrading the image. The current Color Negatives from Kodak offer a range of speeds from E.I. (Exposure Index) 50, to E.I. 800; suitable for conditions ranging from bright sunlight to night exteriors.
The "Color" of Light:
The source of light will determine the color of the light. The color of light will influence the color of subjects photographed in that light. The color of a table lamp will appear more "warm" than light from a morning sky. Candlelight will look "warmer." Although the human eye readily adapts to different types of light, film will record the colors of a scene very accurately. What we consider "Daylight," that is, the mix of light from the sky and sun from two hours after sunrise until two hours before sunset is very different in its "color" than typical household lighting. Florescent lighting has its own pallet of colors.
The color of a given light is expressed as its "Color Temperature." Simply put, the redder, or "warmer" a light source is, the lower its color temperature. The bluer, or "cooler" the light source is, the higher its color temperature. Household light typically measures at about 2,900 Degrees Kelvin on a Color Temperature Meter, and is considered "warm." What we consider "Daylight" is about 5600 Degrees, and called "cool."
"Tungsten" Studio lighting is about 3200-3400 Degrees Kelvin. There is a type of Studio light called "H.M.I.," which is designed to have the color temperature of daylight. Kodak manufactures films that are balanced for either "Daylight" or "Tungsten" light sources.
"Tungsten" films can be shot easily in daylight with the use of an "85 Filter," an orange piece of glass or plastic that changes the quality of the light entering the lens to "Tungsten" color. There is a slight loss of speed, about because about 1/3 of its overall speed has been lost. 1/3 total value. Thus, a film with an E.I. of 200 must be rated at E.I. 125 with the filter in daylight conditions.
"Daylight" films can be shot in tungsten light with the use of an "80A" filter, but this is not recommended because this technique reduces the amount of light striking the film by about two-thirds! An E.I. 250 Daylight Film, like Kodak VISION 250D then loses so much speed that it must be rated at E.I. 64 with the 80A filter in Tungsten light.
Applying the film to the situation:
When choosing or selecting a film, the first question must be, "What is the lighting situation under which the film will be exposed?"
Generally speaking, these two issues will be the determining factors of the film selected. Just as in operating a car, the proper gear is the one will that provide good power and speed at the proper engine revolutions. Thus, the film’s speed should allow exposure that is comfortably within the range of the camera lens for a given lighting situation. Under normal circumstances, the cinematographer does not want to have to open the lens all the way nor close it down all the way, as these settings usually diminish the quality of the picture.
Looking at the numbers:
Lenses are marked according to the amount of light that is allowed to enter. These are referred to as the "F-Stop" or "T-Stop" numbers, and they are mathematically related. Typical "Stops" include F: 2, 4, 5.6, 8, 11, 16, and 22. For each "Stop," or change in lens opening, the amount of light allowed to reach the film is either doubled or halved. The LARGER the "F" value, the SMALLER the amount of light that may pass. Thus, "F-11" allows half as much light to pass as would "F-8."
The speed rating of the film is related in a similar fashion; each doubling of the film speed means twice the sensitivity to light. This means that if a film with a speed of E.I. 100 requires a setting of "F-8" for a given situation, a film rated at E.I. 200 would call for the setting of "F-11," which is one "Stop" more closed. Conversely, a film rated at E.I. 50 would require a "Stop" of "F-5.6" for that scene.
The difference in E.I. 50 to E.I. 100 is one stop. From E.I. 100 to E.I. 200 is also one stop. From E.I. 200 to E.I. 400 would be one stop, also.
In the chart above, the bar at the top represents typical lens openings. The bar below shows the film speed (A.S.A. or E.I.) That would provide the corresponding correct exposure. For example, for a given light situation, the use of a 200-Speed film would require F 5.6. If 100-Speed film were used, the lens would be set at F4. The use of a film with a speed of 500 would require setting the lens betweenF8 and F11.
Slower is finer:
All things being equal, the "slower" the film, the finer the grain and the better the sharpness of the image. VISION Technology has minimized the differences in quality between film speeds, but for cinematographers who desire the best overall image quality, the film with the lowest E.I. than can be used is the best choice.
Bigger is better:
The first rule of image quality is that the bigger the negative area, the higher the quality of the image. This rule assumes that the quality of the cameras and lenses used are equal. That is not to say that a 16mm film cannot look quite good. But the use of 35mm film under identical circumstances will almost always yield a sharper, finer-grained picture with better contrast.
Filters and image quality:
Modern precision filters generally do not detract from the quality of the image being photographed. Still, it is usually desirable to avoid unnecessary layers of glass or plastic in the light path. As a result, the use of "Daylight" film in daylight or H.M.I. light is preferred to the use of "Tungsten" film with an "85" filter.
Sometimes, the added flexibility of using a single film, a "Tungsten" balanced type, in all situations may override the difference in quality a "Daylight" product might offer. The outstanding performance of a film like "5/7274" in many different light situations with proper filtration is one reason for its popularity.
Alternatives:
There is a Color Negative Product that differs somewhat from the rest of the product line, and warrants discussion here. Kodak VISION 320T, 5/7277. This film is designed to have a lower overall level of contrast and color saturation, which will provide:
*Greater exposure "latitude," that is improved ability to handle extremes of brightness and shadow in the original scene.
*More room for "error" in exposure
*A "softer," look, with less brilliant colors
This film might be the choice for the cinematographer who seeks an "alternative" look.
Color Reversal Films:
Color Reversal Films in the past fifteen years have found their prime usage in Student, Government, Consumer, and Industrial markets. Originally the only color product in 16mm, Reversal Films have not enjoyed the technical advancements of their Negative counterparts. There are two major types: Kodachrome and Ektachrome, and within these categories, some variations according to color temperature and speed.
Kodachrome:
Kodachrome was the first practical full-color film, introduced in 1935. It was designed to be a Consumer product first and foremost, although for some years it had some commercial applications. With several refinements, Kodachrome is the same film as that of over sixty years ago; very sharp with excellent grain and outstanding, bright colors. The chemical design of Kodachrome ahs made it an excellent "archival" color material as well. While this film has not been used for many commercial applications: It is made in one Super-8 (Kodachrome 40), and in two 16mm Forms: (Kodachrome 25 Daylight and Kodachrome 40 Tungsten).
Ektachrome:
Ektachrome was designed to be a user (local laboratory) process film. The current Ektachrome motion picture films, called "V.N.F." were designed to be used for newsgathering; (Video News Film). There is only one 35mm Color Reversal film; called "7239" (contrary to typical protocol). There are four 16mm versions of V.N.F. (and one "E-6" "new" Film, available in 35mm only).
These films can serve many purposes:
Far more laboratories process Ektachrome than Kodachrome. Generally speaking, the quality of the V.N.F. images does not approach that of Eastman Color Negative Films. Where image quality is secondary and practicality and economy is primary, VNF Color Reversal Films may be the proper choice.
The 5285, Ektachrome 100D is essentially a "slide film" made in "motion picture form." This film is designed for "E-6" Processing, which differs somewhat from VNF. Consult your laboratory listing for the most current information about processing this film. It is essential that the customer know that this is not an ordinary film, and that special processing (E-6) is required.
Living Black-and-white:
Eastman Black-and-white films are more than just the Industry Standard; they created the Industry. Eastman Plus-X Film, 5231, is the direct successor to its "ancient" relative, 1231, the Nitrate Film on which most of the "Classics" were shot. There are two Negative Films in both 35mm and 16mm, and two Reversal black-and-white 16mm products.
Black-and-white Negative films include Plus-X and Double-X. Plus-X has exceptionally fine grain and excellent sharpness. Interestingly, it has two speed ratings; EI 80 in Daylight, and EI 64 in Tungsten light. Both of these ratings are for use without a filter. The reason for this is the additional blue light present in Daylight, to which the film is most sensitive.
Double-X is Plus-X’s high-speed cousin. While not as fine-grained as Plus-X, it is quite sharp for its speed, again with two ratings; EI 250 in Daylight, 200 in Tungsten. Generally speaking, Double-X is unsuitable for Daylight use without significant filtration because it will be overexposed. It finds its chief applications in the studio when lighting is limited, or in low-light exterior photography.
Kodak also manufactures black-and-white Reversal films, Plus-X Reversal, and Tri-X Reversal. These films are only available in 16mm and Super 8 formats. Unlike their Negative counterparts, these films yield a positive image, suitable for projection or telecine transfer following processing. Kodak also manufactures intermediate and print films to compliment these Reversal films.
Frequently Asked Questions:
Aren’t "grain" and "sharpness" the same thing?
While grain and sharpness are both measure of image quality, they are really two separate characteristics. Grain refers to the image smoothness, and is especially noticeable in broad areas of a solid color like sky or fleshtones. Sharpness refers to a film’s ability to resolve actual detail in the picture. Both of these aspects contribute to the overall look of the picture.
A film can be sharp yet have moderate levels of graininess like Double-X Negative. A film can also have micro-fine grain yet not be as sharp as another film with more visible grain. Actual measurements of these items for each film may be found in the Kodak Publication H-5.
Since Kodak has reduced grain and improved sharpness so much with the new vision films, why not just use a fast film all the time?
The use of a high-speed film can often be a hindrance to the cinematographer if it is used in a bright-light situation. The most obvious problem is that of overexposure. Given enough light, it may not be possible to stop-down enough; a stop of F22 may not suffice. Remedies such as additional filtration can detract from the image quality and darken the viewfinder image, making it difficult for the operator to frame the picture. Additionally, many cinematographers prefer a larger opening to add a feeling of depth.
I know that Super 16 filming requires film perforated on just one edge. What about Super 35?
Super-35 is a format, which utilizes exactly the same film as regular 35mm cinematography. The Super-35 format simply uses a part of the frame area, which ordinarily goes to waste.
Can I use color film for black-and-white cinematography? I may change my mind about the finished film later.
Yes. For television applications, it is simple task to drop the color out during telecine transfer, should a black and white image be desired. It is also possible to achieve this for theatrical projection by using black and white intermediate and/or print films. Examples of this include the features, Dead Again and Pleasantville. It is obviously more expensive to use color materials than black and white materials, however, and the contrast of scenes may appear different.
Isn’t It less expensive for me to shoot my feature film in 16mm and blow it up to 35mm later?
From a raw-stock standpoint it is obviously less expensive to shoot on 16mm film. The real issue becomes the cost of the laboratory work necessary to blow up the 16mm film of the image may be acceptable, it is generally recognized that it will not approach the sharpness and clarity of 35mm-originated images.
Much of the quality associated with 35mm film can be attributed to the class of lenses and the mechanical superiority of the larger film. While the new film emulsions from Kodak offer superb images even in 16mm, the use of 35mm camera film provides an image that is four to five times larger than the 16mm frame. The costs associated with the blow up often offset the rawstock savings.
Another drawback to Super 16mm photography for theatrical release is the inability to project Super 16mm film with a soundtrack. The area on a 16mm print has been used for the additional picture area of the larger frame, prohibiting a composite print (sound-on-film) in Super 16mm. A 35mm blowup, telecine transfer to video, or a special optical reduction print must be made to project a Super 16 feature.
Film Speeds and Shooting Ratios:
Here is a handy quick reference relating to film travel and usage:
Exceptions:
Let’s discuss sound for a moment. Nowadays, a device other than the camera records sound. It may be a specialized portable tape recorder, like the Nagra, a precision on the tape along with the sound record. By doing so, if the tape speed varies slightly during the recording, the crystal signal records this information, making it possible to correct it later. Prior to the Nagra recorder, sound had to be recorded on magnetically coated film stock on a much larger machine with cables running from the camera to the sound recorder for sound sync information.
Another modern way to record sound is with a DAT; a Digital Audio Tape Recorder, whose internal clock mechanism makes ancillary timing devices unnecessary.
After the film is developed, the sound record is transferred to magnetic film of the same width as the camera film (16 or 35mm), to allow for physical cutting in a synchronizer, a device with two or more sprocket wheels locked together by a metal shaft, to maintain synchronization. There are many variations on this theme; some sound tracks remain in their digital form throughout production, and are edited electronically.
S. Garfinkel revision 6/00
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