- This focuses on motion
picture film. For still
photography film, see photographic
film.
Film stock is
photographic film on which
motion pictures are shot and reproduced.
History
1889–1899
Modern motion picture film stock was first created thanks to the
introduction of a transparent flexible
film
base material,
celluloid, which was
discovered and refined for photographic use thanks to the work of
John Carbutt,
Hannibal Goodwin, and
George Eastman. Prior to this, most motion
picture experiments were performed using paper roll film, which
made it difficult if not impossible to view the developed film as a
single continuous moving image without other complex apparatuses.
Furthermore, the paper film was much more fragile than
celluloid.
Eastman Kodak would become the first
to make celluloid film commercially available, starting in 1889;
Thomas Henry Blair emerged in
1891 as the first major competitor for supplying celluloid film.
The stock had a frosted base in order to facilitate easier viewing
by transmitted back light, and the emulsions from each company were
orthochromatic. By November 1891
William Dickson at
Edison's lab was using Blair's stock for
Kinetoscope tests, and Blair's company remained
a main supplier of film to the Edison lab for the next five years.
Blair's operation was also crucial to the continued development of
motion picture technology through 1892 and 1893, due to temporary
shutdowns at Eastman because of problems with their production
setup. Eventually patent lawsuits in 1893 led to Blair leaving his
American company and starting again in Britain, which allowed
Eastman to gradually fill the entirety of the Edison lab's film
orders. Blair's new headquarters allowed him to supply many of the
key European filmmaking pioneers, including
Birt Acres,
Robert
Paul,
George Albert
Smith,
Charles Urban, and the
Lumiere Brothers. The American
Blair company was to be short-lived, however, as by 1896 the new
movie projector would demand a fully
transparent film base that they had difficulty supplying. Eastman
shortly thereafter bought the company out, thus consolidating its
position as the leading supplier of film stock from then on. These
developments also led
Louis Lumiere to
work with
Victor Planchon on
adapting the Lumiere "Blue Label" (Etiquette Bleue) photographic
plate emulsion for use on celluloid roll film, which began in early
1896 and was brought to full production capacity by the following
year.
Eastman's first motion picture film stock incorporated the same
emulsion as was used for its still film, which was, like nearly all
film emulsion of the time,
orthochromatic-sensitive. Film at this point
did not have a strictly defined speed; rather, the orthochromatic
quality of the stock allowed the film to be processed under a red
safelight, while the density was checked
as development was occurring. Standard practice until the end of
the
silent era involved tearing off
several inches from the start of each shot and testing development
on it. Positive stock was created that would be slower,
finer-grained, and of a higher contrast than a negative; all of
these characteristics remain consistent to this day.
From 1895, Eastman supplied their motion picture roll film in rolls
of 65 feet, while Blair's rolls were 75 feet. If longer lengths
were needed, the unexposed negative rolls could be cemented in a
darkroom, but this was largely undesirable
by most narrative filmmakers.
Actuality
films were much more eager to undertake this method, however,
in order to depict longer actions, and created cemented rolls as
long as 1000 feet.
American Mutoscope and
Biograph was the first known company to use this, for the
Jeffries-
Sharkey fight on November 3, 1899.
1900–1919
Work on improved film stocks was rather slow in the first decade of
the new century, as the equipment and
formats, particularly, were still in
the process of gradually standardizing. With a large number of
differing
film gauges in use, supplying a
market still in its infancy was likely a difficult task, and
Eastman was able to retain the majority of the market share without
making major adjustments to the emulsion; their only major change
was to increase the length of rolls to 200 feet. Lumiere, on the
other hand, reformulated their stock to match the speed of Eastman
film, which became known as "Violet Label" (Etiquette Violette).
Blair retired back to the United States after selling his English
company to
Pathe in 1907, who began using the
facilities for producing their own film stock. This sale had future
repercussions among film preservation, as Pathe began to supplement
their operation in 1910 by purchasing film prints in order to strip
the silver and emulsion from the film base for recoating.
As the quantity of film and filmmakers grew in these early years,
the demand for standardization increased in prominence.
35 mm film, largely thanks to the popularity of
the Edison and Lumiere camera lines (and their often unauthorized
clones) had begun to stabilize as the dominant gauge, but still was
usually purchased unperforated, and subsequently punched by the
consumer with perforation equipment designed by third parties.
Although Edison (4 square perfs per frame on each side) and Lumiere
(1 rounded perf per frame on each side) formats - based on the
camera designs - were the most common, the perforators were not
always precise, and it could be difficult to create prints for the
opposite perforation format. Edison's organization of the
Motion Picture Patents Trust, though largely
ineffective in controlling the burgeoning film industry, was able
in 1909 to agree to what would become the de facto standard:
35 mm gauge, with Edison perforations and a 1.33
aspect ratio. These parameters have
remained largely constant to the present day.
The
Bell and Howell company
perforators entered the market in 1908 and very shortly were
recognized as exceptional enough to pervade the American industry.
Eastman Kodak was also quick to opt to use the machine to
pre-perforate their films, which assured the perforation
specifications being adopted as the world standard not long after.
These perforations, known as BH-type, remain the standard for
original camera negative
film.
The
belle epoque era also saw the creation of numerous
small, local film suppliers, the vast majority of which were
short-lived due to their smaller production batches, slower
emulsions (which were also usually blue-only sensitive rather than
orthochromatic), and inferior quality control. Among these
companies,
Agfa began to produce motion picture
film in 1913, but remained a largely local supplier until World War
I boycotts of popular French, American and Italian films allowed
the newly-founded
UFA film studio
to flourish and thus boosted Agfa's orders.
Among the foremost problems with the film stocks of this era was
that they were all manufactured on a
nitrate film base,
which was a derivate of guncotton and thus highly flammable.
Additionally, nitrate fires were notoriously difficult to put out,
as even full submersion in water will not stop the fire. This had
led to a significant number of fatal accidents in theatrical
projection booths, where the heat of the projector lamp made
ignition most likely. As the amateur filmmaking market slowly
developed at the beginning of the 20th century, Kodak began to
develop a more heat-resistant "safety base" which could be easily
projected without incident even at home by those with no prior
experience. Early tests in 1909 showed
cellulose diacetate to be a viable
replacement base, and Kodak began selling acetate-base films the
following year in 22 mm widths for Edison's work on the
Home Kinetoscope, which was
commercially released in 1912. In the wake of the availability of
safety film, more amateur formats began to adopt it, and several,
including Kodak's own
16 mm format, were
designed specifically so that the only film stocks released for the
format specifications would be safety base.
Kodak also continued to refine their camera negative stock during
the late 1910s, releasing Cine Negative Film Type E in 1916 and
Type F (later known as Negative Film Par Speed Type 1201) in 1917.
As both of these orthochromatic films were no faster than previous
offerings, it has been suggested that the improvements most likely
were in regard to granularity and sharpness.
1920s
The 1920s proved to be the decade in which film stock manufacturers
began to diversify their offerings. Prior to this, each
manufacturer only offered one negative stock (usually
orthochromatic) and one print stock. In 1920, a variant of Type F
film known as X-back was created in order to counteract the effects
of static electricity on the film, which can cause sparking and
create odd exposure patterns on the film. This was created through
the use of a resin backing on the film, which also had the effect
of rendering the film too opaque to allow focusing through the back
of the film, a common technique for many of the contemporary
cameras of that era. As the static electricity was more likely to
occur in colder climates, the X-back stock was mainly popular in
the East Coast of the US. Other manufacturers also began to emerge
in the 1920s as well, including American
E.I. Dupont de Nemours in 1926 and Belgian
Gevaert in 1925.
Conversion of the industry from
orthochromatic to
panchromatic stocks was initiated by Kodak over
the course of the decade. Created in 1913 for use in early color
film processes such as
Kinemacolor,
panchromatic was first used in a black and white film for exterior
sequences in
Queen of the Sea (1918) and originally only
available as a special order product. The stock's increased
sensitivity in the red-light range meant greater overall light
sensitivity and made it an attractive option for
day for night shooting. Kodak financed a
feature in 1922 shot entirely with the panchromatic stock,
The Headless
Horseman, in order to promote the stock when it was
introduced as a standard option; however, the fairly higher price
of the stock compared to the orthochromatic emulsion meant that no
other films would shot entirely with the panchromatic stock for
several years. The cross-cutting between panchromatic and
orthochromatic stocks also was noted to cause continuity problems
particularly with regard to costume tones, and thus was often
avoided. The dominance of orthochromatic film lasted until the mid
1920s due to Kodak's lack of competition in the panchromatic
market; Gevaert emerged onto the market in 1925 with a dual product
line of an orthochromatic stock with limited color sensitivity as
well as a full panchromatic stock, Pan-23. This latter product
likely encouraged Kodak to respond, and in 1926 they lowered the
price of panchromatic stock to parity with the standard
orthochromatic offering. Without any economic barrier remaining,
the panchromatic stock began to overtake the orthochromatic stock's
market share within a few years, as the cinematographers gradually
became more familiar with the stock. With similar panchromatic
offerings also made around the same period by Agfa and Pathe, the
shift to panchromatic stocks had largely been completed by 1928,
and Kodak discontinued orthochromatic stock in 1930.
Color films
Experiments with color films were made as early as the late 19th
century, but practical color film was not commercially viable until
1908, and for amateur use when Kodak introduced
Kodachrome for 16 mm in 1935 and 8 mm
in 1936.
Before 1941, commercially successful color processes used special
cameras loaded with black and white separation stocks rather than
color negative.
Kinemacolor (1908–1914),
Technicolor processes 1 through 4
(1917–1954), and
Cinecolor used one, two
or three strips of monochrome film stock sensitized to certain
primary colors or exposed behind color filters in special
cameras.
Technicolor introduced a color
reversal stock, called Monopack, for location
shooting in 1941; it was ultimately a 35 mm version of
Kodachrome that could be used in standard motion picture cameras.
Eastman Kodak introduced their first 35mm color negative stock,
Eastman Color Negative film 5247, in 1950. A higher quality version
in 1952, Eastman Color Negative film 5248, was quickly adopted by
Hollywood for color motion picture production, replacing both the
expensive three-strip Technicolor process and Monopack.
Classification and properties
There are several variables in classifying stocks; in practice, one
orders raw stock by a code number, based on desired sensitivity to
light.
Base
A piece of film consists of a light-sensitive
emulsion applied to a tough, transparent
base, sometimes attached to
anti-halation backing or "rem-jet"
layer (now only on camera films). Originally the highly flammable
cellulose nitrate was used. In the
1930s, film manufacturers introduced "
safety
film" with a cellulose triacetate plastic base. All amateur
film stocks were safety film, but the use of nitrate persisted for
professional releases.
Kodak discontinued the
manufacture of nitrate base in 1951, and the industry transitioned
entirely to safety film in 1951 in the United States
and by 1955 internationally. Since the late
1990s, almost all release prints have used
polyester film stock.
Emulsion
The emulsion is comprised of
silver
halide grains suspended in a
gelatin
colloid; in the case of color film, there are three layers of
silver halide, which are mixed with
color
couplers and interlayers that filter specific light spectra.
These end up creating yellow,
cyan, and
magenta layers in the negative after
development.
Chemistry
Development chemicals applied to an appropriate film can produce
either a positive (showing the same densities and colors as the
subject) or
negative image (with dark
highlights, light shadows, and, in principle, complementary
colors). The first films were darkened by light: negative films.
Later films that produce a positive image became known as
reversal films; processed transparent film of
this type can be
projected onto a
screen. Negative images need to be transferred onto photographic
paper or other substrate which reverses the image again, producing
a final positive image. Creating a positive image from a negative
film can also be done by
scanning the
negative to create a computer file which can then be reversed by
software.
Image record
Different emulsions and development processes exist for a variety
of image recording possibilities: the two most common of which are
black and white, and color. However, there are also variant types,
such as
infrared film (in black and
white or
false color); specialist
technical films, such as those used for
X-rays; and obsolete processes, such as
orthochromatic film. Generally, however, the
vast majority of stock used today is "normal" (visible spectrum)
color, although "normal" black and white also commands a
significant minority percentage.
Physical characteristics
Film is also classified according to its
gauge and the arrangement of its
perforations— gauges range from
8 mm to
70 mm or more,
while perforations may vary in shape, pitch, and positioning. The
film is also distinguished by how it is wound with regard to
perforations and base or emulsion side, as well as whether it is
packaged around a core, a daylight spool, or within a cartridge.
Depending on the manufacturing processes and camera equipment,
lengths can vary anywhere from 25 to 2000 feet. Common lengths
include 25 feet for 8 mm, 50 feet for
Super 8, 100 and 400 feet for 16 mm,
400 and 1000 feet for 35 mm, and 1000 for 65/70 mm.
Responsivity
A critical property of a stock is its
film
speed, determined by
ASA or its sensitivity to
light listed by a measurement on the
raw
stock which must be chosen with care. Speed determines the
range of lighting conditions under which the film can be shot, and
is related to
granularity and contrast,
which influence the look of the image. The stock manufacturer will
usually give an exposure index (EI) number equal to the ASA which
they recommend exposing for. However, factors such as forced or
non-standard development (such as
bleach
bypass or
cross processing),
compensation for filters or
shutter
angle, as well as intended under- and over-exposure may cause
the cinematographer to actually "rate" the stock differently from
the EI. This new rating is not a change to the stock itself - it is
merely a way of calculating exposure without figuring out the
compensation after each light reading.
Color temperature
Another important quality of color film stock in particular is its
color balance, which is defined by the
color temperature at which it
accurately records white.
Tungsten
lighting is defined at 3200 K, which is considered "warmer" in
tone and shifted towards orange;
daylight
is defined at 5600 K, which is considered "colder" and shifted
towards blue. This means that unfiltered tungsten stock will look
normal shot under tungsten lights, but blue if shot during
daylight. Obversely, daylight stock shot in daylight will look
normal, but orange if shot under tungsten lights. Color temperature
issues such as these can be compensated for by other factors such
as lens filters and color gels placed in front of the lights. The
color temperature of a film stock is generally indicated next to
the film speed number - e.g. 500T stock is color film stock with an
ASA of 500 and balanced for tungsten light; 250D would have an ASA
of 250 and be balanced for daylight.
While black and white film has no color temperature itself, the
silver halide grains themselves tend to be slightly more responsive
to blue light, and therefore will have daylight and tungsten speeds
- e.g. Kodak's Double-X stock is rated 250D/200T, since the
tungsten light will give slightly less exposure than an equivalent
amount of daylight.
Deterioration
All plastic is
subject to
deterioration through physical or chemical means, and thus,
motion picture film is subject to the same deterioration. Cellulose
nitrate, cellulose diacetate and triacetate are known to be
unstable mediums: improperly preserved film can deteriorate in a
period of time much faster than many photographs or other visual
presentations.
Cellulose nitrate, because of its unstable chemistry, eventually
breaks down, releasing nitric acid, further catalyzing the
decomposition. In the final stages of celluloid decomposition, the
film turns into a rust-like powder.
Likewise, tri-acetate stock is not invulnerable from deterioration.
Because of the small gauge of the film, owners of home-made films
often find that their film can become shrunken and brittle to the
point where the film is unwatchable in the space of a few years. In
general, decaying acetate film breaks down into
acetic acid, and similar to celluloid
decomposition, leads to an auto-catylictic breakdown of the base
that cannot be reversed. The result of the acetic acid released is
a strong odor of
vinegar, which is why the
decay process in the archival community is known as "
vinegar syndrome."
Modern polyester-based stocks are far more stable by comparison and
are rated to last hundreds of years.
Intermediate and print stocks
The distinction between camera stocks and print stocks involves a
difference in the recording process. When the work print or edit
master has been approved, the original camera negative (OCN) is
assembled by a
negative cutter using
the edited work print or EDL (edit decision list) as a guide. An
answer print is then made from the cut negative. During the answer
print stage, corrections in the film's density and color are
corrected (timed) to the filmmakers' tastes. Interpositive (IP)
prints are struck from the answerprint, checked to make sure they
look the same as the custom timed answer print and each IP is then
used to make one or more Dupe Negative (DN) copies. The
release prints are then generated from the
DN(s). Recently, with the development of
digital intermediate (DI), it has
become possible to completely edit, composite visual effects, and
color grade the image digitally at full resolution and bit-depth.
In this workflow, the answer print is generated digitally and then
written out to the IP stage using a laser film printer.
Due to the specialized nature of the exposure and the higher degree
of control afforded by the film lab equipment, these intermediate
and release stocks are specially designed solely for these
applications and are generally not feasible for camera shooting.
Because intermediates only function to maintain the image
information accurately across duplication, each manufacturer tends
to only produce one or two different intermediate stocks.
Similarly, release print stocks usually are available only in two
varieties: a "normal" print or a deluxe print (on more-costly print
film like Kodak Vision Premiere) with slightly greater saturation
and contrast.
See also
Notes
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