| Figure 48 |  |
Unprocessed Film
The label contains the characteristics of up processed film.
The eleven-digit code on the label in Figure 49 (5247-123-4567) identifies the film type (5247), the emulsion batch number (123), and the number of the roll (4567) from which this strip of EASTMAN Color Negative Film was cut. The emulsion batch number and roll number also appear on the tape sealing the can.
The Film Identification code (ECN 718 in this case) gives the emulsion type (ECN or EASTMAN Color Negative Film) and film specification number (718), a code describing width, perforation type and format, winding, and type of core, spool, or magazine.
The film width, perforation pitch, and emulsion position and winding type are identified on the label.
The film-strip reference number identifies the location of a particular strip of film cut from the master roll. This number (1 through 38 for 35 mm and 1 through 83 for 16 mm) appears on a sticker affixed to most cans holding 400 or more feet of film. Figure 48 shows such a sticker.
| Figure 48 | |
Processed Film
The film strip reference number affixed to the can of raw stock film also
appears as a latent image on the film itself. It is visible on the processed film
between "EASTMAN" and "SAFETY FILM" on the edge print.
On 35 mm films having multiple-row perforations (used only by processing laboratories to print multiple copies of a film simultaneously), a lowercase letter or letters (a, b, c, etc) appear between "SAFETY" and "FILM" to identify the perforation format of the parent strip and the location of the sub strip within it.
The combinations of manufacturer's code (an uppercase letter for 35 mm or a trailer-end marking for 16 mm), film base data, and edge-print medium (ink or latent image) are helpful in identifying processed film. If a film data sheet carries a "Film Identification" heading, the uppercase letter of the manufacturer's code will be listed.
Know Your Films
Design, manufacture, actual shooting, projection, and storage conditions all
influence film performance and selection.
First we'll discuss why an on-site test is a good idea. Suppose your test
shows that the film stock being considered produces unattractive results
under the lights you plan to use to illuminate a few scenes. Will a filter
correct the situation? Can you change the lighting? Will another film stock
work better for those scenes?
Our second topic, filtration, covers the wide range of uses for filters to fill the needs of your unique circumstances.
The third section covers the process by which the sound you recorded is combined with your images in the final print.
The last two sections explain how to care for the finished films you have carefully created.
Test Exposures
Every production presents a unique set of conditions and demands. A full
understanding of the job at hand and careful evaluation of the information in
the data sheets should give the filmmaker a good idea of how a chosen film
stock will respond to most filming situations. Testing reduces any remaining
uncertainties and establishes the reaction of a particular film to a unique
situation. Tle variations that make test exposures worthwhile and the
technique of interpreting such exposures are the subjects of this section.
Testing is one aspect of professional work too often overlooked in practice.
When seeking the best possible results, filmmakers should run tests to
provide reference points during production and to confirm choices based on
previous experience and data sheet information.
Here, listed in the order of the time they may occur, are the principle causes of real or apparent changes in speed in all films, and contrast and color balance in color films. Failure to understand these causes can lead to misunderstanding or misinterpretation of photographic results:
All except the first are beyond the scope of manufacturing control and cannot be predicted accurately from the data sheets. Furthermore, the variations encountered in practical use are apt to be a great deal larger than those permitted by manufacturing tolerances. These are the basic reasons why you should make a test exposure whenever speed and color-balance are important. Test exposures are necessary for reversal materials that will be projected directly after processing more so than for negative or printed reversal materials because density and color-balance adjustments cannot be made during printing.
Most professionals realize the perishable nature of sensitized materials and are careful to avoid subjecting films (especially color) to extreme heat and humidity, either before or after exposure. The other factors listed are equally important, however, even if not equally familiar. None should ever be overlooked when choosing a film or attempting to explain an unexpected result.
Two or more causes of variation may influence results at the same time. Often the effects are additive, and minor single variations will, when combined, produce noticeable results unless proper compensation is made in advance. Only a test exposure under the practical conditions of use will furnish this information.
To Provide a Reference Point
A speed variation of 1/3 stop, and sometimes more, usually passes unnoticed
when black-and-white film is projected. In a color film, where the
performance of each emulsion layer is evaluated in terms of the other two, a
much smaller variation in the relative speed of any one layer is evident to the
user.
Coating thickness is a manufacturing variable that provides an excellent
illustration of the technical accuracy maintained in making color films.
Tests have shown that the thickness of each emulsion layer must be
controlled within 4 or 5 percent; any larger variation would by itself use up
the entire color-balance tolerance available.
Since a typical color emulsion is only 3 ten thousandths of an inch thick, so only 15 millionths of an inch variation is allowable. And this kind of accuracy is maintained in making successive coatings on a thin, flexible base in the dark!
Every effort is made to achieve the greatest possible uniformity in the manufacture of Kodak films, but within such close tolerances minor variations are unavoidable. Of course, variations are smallest among films of the same emulsion number. In any case, test data obtained under actual production conditions is recommended to supplement the manufacturer's data.
At Kodak, the standardization of manufacturing operations is supplemented by an extensive testing and quality-control program. Only film produced within narrow tolerances of the production aim point is shipped from the manufacturing plant.
The actual sensitometric tolerances tested include speed, fog, contrast, color-contrast match, and maximum density. Production tests are made at normal room temperature with illuminants equivalent in color quality to tungsten (3200 or 3400 K) lamps for tungsten films and to average sunlight plus skylight (5500 K) for daylight films. They are exposed at times considered representative of the major applications for the films. In all cases, films are processed in accordance with process specifications. Physical characteristics such as curl, perforation pitch, weave, tensile strength, freedom from scratches, etc., are also carefully controlled.
With EASTMAN and KODAK EKTACHROME Films, the permitted color-balance variations, tested under normal recommended use, fall approximately within the range correctable by a CC10 filter in the camera exposure. In the case of negative films, normal color-balance variations fall within a range for which adjustment can easily be made in the printing process.
The careful cinematographer should make practical picture tests on new film batches with the exposure and filtration to be used for the rest of the production. These tests will help to determine if any additional filtration and exposure adjustments are needed.
For Locations with Unfamiliar Lighting
Filmmakers are well aware that color films are balanced in manufacture for
exposure to light of a certain color quality. Color negative film offers
considerable latitude because some adjustments for color balance you can
make during printing. Even reversal materials that will be printed offer
some latitude because of the printing step. However, when a reversal
material isn't going to be printed, you must make compensation if the light
source differs in color quality from that for which the film is balanced. Even
the "correct" light may be changed appreciably in color quality as it passes
from source to subject to film. Discolored or dirty
reflectors and camera lenses with a color tint can change color quality.
Furthermore, the color quality of tungsten and fluorescent lamps can change
with age and voltage fluctuations. Lighting from mixed sources will also
change color renderings.
To Establish a Reference with You and Your Laboratory
Different laboratories can produce noticeable variations in image quality and
effective film speed, and from time to time variations can be noted at a
single laboratory. Typical processing can result in speed variations of plus
or minus 1/2-stop and color-balance variations on the order of +/-CC10 filter.
Tests processed by your chosen laboratory serve as a base in all future
discussions with the laboratory.
To Evaluate Specific End-Use Appearance
The conditions under which film is viewed have a marked effect on the
apparent color quality of the picture. For critical applications, test film
should be projected and evaluated under the specific conditions in which it
will be used. The locations of the projector, the viewer, and the screen can
affect the image quality dramatically.
To Determine the "Look" of the Finished Job
Because the viewers' reactions to a projected image involve their
psychological responses, a projected image can never be "perfect' in any
simple sense.
Like all photographic and electronic imaging systems, Kodak color films exhibit small color differences between the image and the subject itself when they are critically compared. Usually these differences are insignificant, but cinematographers have to judge whether the "look" of the film is consistent with their intentions and with the nature of the subject.
Since the manufacturer's evaluation of color balance is determined from picture tests judged by a number of observers, it is obvious that an individual cinematographer, producer, or laboratory may prefer a color balance different from one judged desirable by the manufacturer.
Because the manufacturer can never judge color balance appropriately for all tastes and all extremes of working conditions, critical work should be preceded by tests made as closely as possible to the conditions of final use, if possible, on the actual subject. You should always make the test on film of the same emulsion number as that to be used for the final exposure and kept under similar conditions before and after exposure. The exposure time, light source, and processing conditions should also be identical with those planned for the final work.
To Check Specific Color Reproduction
With only three dyes, color films are, able to produce a pleasing rendering of
most colors. Occasionally, though, some colors present special difficulties
in accurate reproduction, even though the film has been manufactured,
stored, exposed, and processed correctly. Fortunately, the conditions that
produce these effects are not common.
Since a large majority of all photographs include people, the reproduction of flesh tones is a primary consideration in the design of a color film. Also important are the reproduction of neutrals (whites, grays, and blacks) and the reproduction of common "memory" colors, such as blue sky, green grass, etc. Because films are designed to reproduce these colors properly under a variety of conditions, some other colors-such as shades of chartreuse, lime, pink, and orange-may reproduce less well. (It is possible to design a film that would improve the reproduction of these other colors, but only at the expense of generally more important flesh tones, sky, grass, etc.) More noticeable difficulties can be encountered because color films do not have exactly the same color sensitivities as the human eye. For most subjects, the three light-sensitive layers of the film do not have to "see" the subject exactly the same way the human eye does. In most cases, the differences are scarcely noticeable.
Sometimes, though, the differences between film sensitivity and visual sensitivity produce unwelcome results. Since color films are sensitive to ultraviolet radiation, a substance reflecting ultraviolet energy will reproduce bluer on film than it looks to the eye. If it is blue to begin with, this effect is of little or no consequence. With other colors, however, the additional blueness may neutralize the original color or even make it appear blue. Neutral and near-neutral colors are more apt to be affected by such a shift, because their saturation is low. For example, a black tuxedo made of synthetic material may appear blue. An ultraviolet absorbing filter, such as a KODAK WRATTEN Gelatin Filter No. 2B, over the lens or over the light source when practical can reduce this effect.
Closely related is the effect of ultraviolet fluorescence. Some fabrics absorb ultraviolet radiation and remit it in the near-blue (shortest wavelength) portion of the visible spectrum. Since the eye is not very sensitive in this part of the spectrum, the effect may not be readily apparent until a photograph of the subject is viewed. An analogous visual effect is created by black light which makes special paints, some fabrics, etc, glow in the dark.
Under an ultraviolet lamp, any fabric containing brighteners will fluoresce, but many white fabrics contain brighteners introduced during manufacture or laundering to give them a whiter appearance. Examination of any suspect fabrics under an ultraviolet source will generally indicate whether there will be a fluorescence problem. In this case, a filter over the lens does not help; however, an ultraviolet absorber over the light source may prove helpful. A photographic test is the best way to determine whether problems with reproduction in the ultraviolet range should be anticipated.
Perhaps most troublesome are the color reproduction problems sometimes called anomalous reflectance. They arise from high reflectance at the far red and infrared end of the spectrum, where the eye has little or no sensitivity. The heavenly blue moming glory and ageratum flowers are examples of colors occurring in nature that reproduce poorly because color films are much more sensitive to the far red than the eye. Among artificial materials, some classes of organic dye are notable examples of high reflectance in the far red. These dyes are currently very popular with fabric manufacturers because they are relatively inexpensive and work well with synthetic materials. While the high reflectance of these dyes in the far red and infrared can be found in all colors, its effect is most noticeable in medium to dark green fabrics, where the photographic effect of the far red reflectance is to neutralize the green, making it appear browner.
You can identify high reflectance at the far end of the spectrum can be
identified by use of a deep red filter such as a KODAK WRATTEN Gelatin
Filter No. 70. If the materials are examined under a tungsten light, a green
natural-fiber material will appear black, whereas a synthetic material with
high reflectance in the far red will appear much lighter. Because the
judgment is quantitative, a sample of a green fabric known to reproduce well
should be compared with the test fabric under the filter. If the test fabric
appears distinctly light in a side-by-side comparison through the No. 70
filter, you should expect a reproduction problern. Even then, confirmation
by means of a photographic test under actual working conditions is advisable
if circumstances permit.