THE STORY OF THE PERFORATION GAUGE
We have seen that before the film can be used in the camera it has to
be perforated on either side in order that successive areas of film ¾
of an inch deep--the equivalent of a picture--can be seized and brought
into position behind the lens. This perforation has become standardised
in accordance with what is known as the “Edison Standard Gauge,” which
is 64 perforations per foot on either side. This perforation is of an
elongated form, measuring about ⅛ of an inch in width by approximately
1/16th of an inch in depth.
The preliminary operation is carried out with a machine, which stamps
the holes by means of specially hardened steel punches. Extreme care
has to be taken to carry out the task with mathematical accuracy, in
order that the film may be used with any type of camera and projector.
Without it steadiness of the picture upon the screen is absolutely
impossible.
It seems strange that all films should have to be perforated according
to the Edison system, when it is remembered that the first commercial
cinematographic apparatuses for the projection of pictures upon a
screen were made, not by Edison, but by Paul and Lumière, who, one
might think, would have established their own gauges. This important
point involves an interesting little story.
In the very earliest days of cinematography, when a film of greater
width was used than at present, it was advanced by friction. Rollers,
or clutches, gripped the edges of the film tightly, and moved it
forward the desired extent. But their action was uncertain. Sometimes
the rollers became slack and the film slipped, the celluloid ribbon
varied in thickness or was a trifle slippery, with the result that
the forward movement was irregular, and the pictures did not appear
in rhythmic succession. Some were askew, others were overlapped by
the preceding or succeeding image, or a wide gap was left between
consecutive pictures.
In order to overcome the drawback, attempts were made to devise a
system of moving the film forward by the aid of pins engaging with
holes in the sides. But the apparatus employed was mechanically
defective. The film dragged, and the holes were either torn or became
so worn that they did not engage accurately. Square holes were
first tried, but the wear and tear set up by the pins or sprocket
teeth soon gave them a circular or elongated shape. Then circular
perforations were adopted, but they soon became elliptical. The
number of perforations per picture was varied also in the hope of
securing steadiness of the film both in the camera and more especially
in projection, but every effort appeared to refuse to remove the
difficulty.
One of the early investigators was discussing the subject one night
with Lord Kelvin. The eminent scientist became deeply interested in
this trouble with regard to the perforations, and the disadvantages of
the respective shapes shown to him. After a few minutes’ reflection, he
remarked, “Why not use perforations of triangular form? They will not
wear round or square. They will always retain their shape more or less,
and at all events will give improved steadiness in running.” The advice
of Lord Kelvin was followed, and the triangular holes were found to
give the best results achieved up to that time.
Meanwhile the shape of the perforations and the gauge had settled
itself in a curious manner. The kinetoscope appeared with small
rectangular perforations, numbering four to each picture, on either
side of the film. Edison had settled on this plan for his apparatus,
finding that it afforded him the best results. The machines were made
and despatched to various parts of the world. To maintain the interest
in the novelty, a number of films were prepared and sold to various
customers possessing the kinetoscope.
When Messrs. Lumière brought out their projecting apparatus, only
one brand of film available for demonstration purposes was on the
market--that made for the kinetoscope. When Paul first entered the
manufacturing field, he, of course, prepared films for use with the
kinetoscope of his own manufacture, and he naturally adopted Edison’s
gauge. As already narrated, Lumière made an attempt to set up an
independent gauge, with one hole each side per picture, but the
Edison and Paul films with an identical gauge had become too firmly
established, especially as the famous American inventor commanded
the situation in the United States. There was no market for either
machines or films deviating from Edison’s gauge. Exhibitors who had
bought kinetoscopes and films, when they acquired a Lumière projector,
demanded that it should be so designed as to use the films which
they owned already, and which were highly expensive. When other
film-picture manufacturers entered the arena they followed in Edison’s
footsteps, because there was no market for their wares if they did
otherwise. Consequently the Edison perforation gauge became more and
more firmly established as time progressed, until at last it became
regarded as the standard. It must be pointed out that this result was
largely attributable to Paul, who became the largest manufacturer of
kinetoscope films in the world.
Yet it must not be thought that the settlement came about smoothly.
There has been a battle of the gauges in the cinematographic as in the
railway world. The Edison standard gauge has its admitted drawbacks,
the greatest of which is that there are too many holes per picture,
which weaken the film and tend to precipitate tearing. Two, or even
one, hole per picture on either side would suffice, as demonstration
has conclusively proved.
An American rival attempted to swerve from the standard in another
direction, using a film 2¾ inches wide--double the width of the
kinetoscope film. He eventually abandoned the wide band, partly on
economic grounds, as a ribbon half the width produced pictures in
every respect equal to those obtained from the wider film. On one or
two occasions the gauge has been revised slightly, but the variations
merely affected the dimensions of the hole to a microscopic degree.
Fundamentally, the gauge as set by Edison for the first commercial
apparatus for showing photographs in motion prevails to-day, and is
universally accepted.
The film is received from the manufacturers in a plain ribbon, and the
perforation has to be done shortly before the film is taken in hand for
exposure. The film manufacturers cannot possibly supply it perforated,
because the celluloid base undergoes continuous physical change while
in storage. Under varying climatic conditions it shrinks and expands
to an extent which may not be observable to the eye, but becomes
pronounced when the picture is projected upon the screen.
The necessity for mathematical precision in the matter of perforating
is somewhat obscure to the uninitiated, but its effects may be
demonstrated very easily. Compare the vibrating or oscillating
flickering picture of 1896 with that shown upon the screen to-day,
in which the effect produced comes very close to that of the _camera
obscura_. If the perforation errs the hundredth part of an inch,
steadiness in the picture is forfeited. The films have to be punctured
with the same mathematical accuracy that goes to the production of a
tiny screw intended for the most delicate piece of mechanism.
[Illustration: PAUL’S ROTARY PERFORATOR.
To punch the holes in the margins of the film before it is exposed.]
[Illustration: THE FIRST CINEMATOGRAPH STUDIO-STAGE.
Built by Robert Paul, at New Southgate, London. It faced north. The
camera and operator were mounted on a platform which travelled upon
rails.
_See page 104._
]
This is especially the case in regard to the perforation of the
negative film. If this is not absolutely true to gauge, the existing
error will be magnified in the passage of the film through the camera;
and should the latter be ever so slightly at fault, the defect
becomes intensified still more. By the time the picture reaches the
projector the infinitesimally small defect in the first instance
becomes increased fourfold or even more. The picture will jump and
flutter in the most distressing manner, and no matter how dexterous the
operator may be, and despite the excellence of his projector, he cannot
by any means rectify or mitigate very appreciably defects arising from
indifferent perforation.
The contribution of imperfect perforation to unsteadiness in projection
was recognised in the earliest days; and great technical skill was
devoted to the elaboration of machines to puncture the film with
scientific precision. Marvellous appliances have been produced for this
purpose; but despite the infinite labour bestowed upon their production
the possibility of error is ever present. Still, it has been reduced to
infinitesimal proportions, and, given a careful operator, a film can be
perforated with the holes varying not a thousandth part of an inch from
the gauge.
The very earliest type of perforating machine was known as the “Rotary
Perforator,” Paul leading the way in this, as in several other
ramifications of the industry. The machine was driven by a mechanism
identical with that utilised in the camera and projector; because the
film had to be advanced intermittently beneath the punches, which were
provided with an oscillating movement. This type of machine is shown
in the illustration. Paul’s first appliance has always ranked as more
simple, efficient, and reliable than any other.
During recent years the rotary perforator has fallen from favour,
on the plea that it soon becomes imperfect in working; but such an
accusation cannot fairly be brought against Paul’s machine, since its
designer used it continuously for four years, during which time it
punched millions of holes, and to-day is as correct in its work as when
first used.
It is impossible within the scope of this book to describe all the
various types of perforation apparatus now in vogue, more especially as
their interest lies mainly in highly technical details. I will content
myself with describing three machines which exemplify the three most
important methods of perforation.
As this operation has to be carried out in the dark room in the dim
light of a ruby lamp, it is imperative that the machines should be of
the most simple design and operation, demanding the minimum of labour
on the part of the operator.
[Illustration: THE WILLIAMSON FILM PERFORATOR.
_For explanation of design and operation see page 62._
]
In the Williamson perforator, four holes on either side of the film
are punched at one time, and two films are perforated simultaneously,
the sensitised surfaces being face to face. This arrangement obviates
the danger of scratching or rubbing the sensitised surface during the
operation. One coil of plain film is mounted on the spool _A_, and
another on the lower spool _B_. The leads from these two spools are
taken between the rollers _C_ on to a small platform or guide gate _D_,
where the two superimposed films are brought accurately together to
pass under the punches. These are mounted in two rows, the requisite
distance apart, in a moving head piece _E_, which descends at the
critical moment, the punches piercing the films cleanly and sharply,
the pieces of detached celluloid falling into a receptacle on the floor
beneath.
When the head containing the punches rises, the two hooked fingers or
claws _F_ engage a hole on either side of the films, and pull them
forward ready for the punching of the next four pairs of holes. In
addition to carrying four pairs of punches, the head _E_ carries four
pairs of projecting pins, set to the same gauge, and before the punch
descends these guide pins engage with the four preceding pairs of
holes, so that the distance between the sets of four holes on either
side is bound to be exactly the same as between any two consecutive
holes made simultaneously. The result is that the holes are perforated
with absolute mathematical accuracy.
As the film emerges from the perforator proper, it is passed between
two guide rollers and a toothed sprocket _G_, which meshes with the
perforations, and thence the lower film passes to the re-winding spool
_H_, and the upper film to the spool _J_. Between the perforating plate
and the respective rollers _C_ and _G_, small loops will be observed.
These are provided for the purpose of obviating any pull upon the
film while in the guide gate, and beneath the punches, which might
otherwise destroy the alignment and accuracy of the gauge. These loops
remain constant, but they can be altered at will while the machine
is running without disturbing the actual perforation. The Williamson
perforator can be run under power at a relatively high speed, the wheel
_K_ being capable of 400 revolutions per minute without impairing the
accuracy of the work in the slightest degree.
[Illustration: FIG. 5.--THE N.S. FILM PERFORATOR.]
A different type of machine is represented in the “N.S.” perforator,
Fig. 5. In this instance the coil of plain film _A_ is set up in a
convenient position away from the machine, but in such a manner that
the feed thereto is in an easy curve. The film enters the machine
through two roller guides, _C_ and _D_, to a channel _F_, and then
under the dies in the top plate _L_. The punctured pieces of film fall
away clear of the instrument through the tube _N_, so that there is no
probability of such particles fouling the mechanism and thus possibly
upsetting the accurate working of the apparatus. After being perforated
the film is moved forward by means of guide pins, and finally issues
through a guide _B_ to be re-coiled. This apparatus is very convenient
for driving by power, is simple, efficient in its operation, and owing
to the solidity of its construction there is little possibility of
the precision of the gauge being upset by wear and tear, or by other
external influences. The gauge, moreover, can be altered, if desired,
to as small a degree as 1/100th of an inch per foot. As the positive
film shrinks somewhat after development, it is an advantage to be able
to compensate for the contraction when perforating. When the film is
dry, although it may have shrunk a trifle, it is found that the gauge
is perfectly accurate.
In the Urban-Joy perforator, only a single pair of holes is punched
at a time--one on either side of the film. At first sight this method
appears somewhat slow, but there is the distinct advantage that the
holes are made with incontestable scientific precision, and after all
this is the all-important factor. This machine is capable of the very
finest adjustment, it being possible to vary the stroke of the punch to
the millionth part of an inch. Its simplicity of operation is another
distinct point. All strain upon the film is avoided for the simple
reason that it is passed through the machine by the pendulum action of
the punches. When these are disengaged the film is held in position by
a clamp working in opposite step to the action of the punches.
Years of labour have been expended upon the evolution of the
perforator. The fruit of these efforts, however, is a material
improvement in the steadiness of the picture upon the screen.
[Illustration: THE PERFORATING ROOM OF THE CINES COMPANY IN ROME.
The operation has to be carried out in ruby light.]