THE FILM.
_Film Making and Characteristics._--All film is of celluloid. The
commercial film used for the projection of motion pictures comes in long
strips, is about one and three-eighths inches wide, and about one
two-hundredths of an inch thick. Upon one side of this film is a
photographic emulsion of gelatine impregnated with a solution of bromide
of silver. This silver is sensitive to the light and has the property of
turning black, during the process of developing, in proportion to the
quantity of light that has struck the different parts of the emulsion.
Wherever the light has been very intense or has been applied for a
sufficiently long time, the film, after treatment with a proper
developing fluid, becomes very black; where no light has reached it, it
remains white; and in the intermediate portions, the shading is in
proportion to the light that has reached those parts.
Film that has not been exposed and developed is of a creamy yellowish
color and, if immersed in a solution of hyposulphite of soda, will turn
perfectly clear and offer no obstruction to the light. If, on the other
hand, it is completely exposed and developed, it will become solid
black; such black pieces are sometimes used as leaders and tails in
connection with motion pictures.
The emulsion on the film melts at a temperature of about 90 degrees
Fahrenheit and will then run off the film. It is also soluble in warm
water. The celluloid of the film is very inflammable and bursts into
flame at a temperature of 284 degrees Fahrenheit. If it is ignited while
tightly wound upon a reel, it burns somewhat slowly; if it is ignited in
a tank, the beginning of the fire is also slow; but as soon as the air
in the tank attains the proper temperature, the whole of the film bursts
into flame at once. It acts in this respect very much like gunpowder. In
burning, the film gives off a dense brownish mass of poisonous smoke.
Film will burn even when it has no access to the air and a film fire
cannot be put out by smothering.
Before sending out their films, the manufacturers treat them with
glycerine. This is for the purpose of keeping them pliable as long as
possible. In time, however, a film dries out and there is then very
little that can be done with it. At any rate, whatever is to be done
should be done by the exchange, as no operator has facilities for
handling it.
Some films are waterproofed and a little water will not damage them
much; but other films must be kept dry. If by accident a roll of film
should become wet, it can be saved by very quickly unrolling it and
spreading it out to dry. If it can be spread out quickly enough, it will
not be harmed; but if it is not spread out at once, the emulsion will
stick to the celluloid and will come off when the film is finally
unwound.
There is also a process of fireproofing film. This must not, however, be
too thoroughly relied upon, especially if the film is old. Fireproof
film is a valuable aid, but it is best to treat it exactly like other
film in respect to the fire hazard.
On account of its inflammable character, film should always be kept in
fireproof enclosures.
The film contains sixteen pictures to each foot and for every picture
there are four sprocket holes on each side of the film. The size of the
aperture plate and also the size of the actual picture on the film is
11/16 inch high by 15/16 inch wide. If the picture on the screen is
enlarged to 18 feet 9 inches in width and 13 feet 9 inches high, every
part of the picture on the film will appear 57,600 times as large on the
screen as it is in the film. In viewing a 1000-foot film, the audience
will see 16,000 separate pictures following each other so rapidly that
the change from one to the other will be unnoticeable. If a three-blade
shutter is used, the beholder will see the light shut off and turned on
48,000 times in the same run of film, but will not be able to notice it
if the speed with which it is done is correct.
New film coming directly from the exchange is likely to be too moist and
cause trouble from that condition; while old film is likely to be too
dry and cause trouble by warping or bending out of shape.
_Patching Film._--All reels of films contain patches and but little
trouble will arise from them, provided they are properly made and
reasonable care is exercised in watching them. In order to obtain a
satisfactory splice, it should not be made more than 3/16 inch long; a
greater length than this will reach two sprocket teeth and this is
objectionable because the splice stiffens the film and will prevent it
from fitting the teeth properly. The splice should be so made that it
does not throw the pictures out of frame. If made properly, it will
never be noticed in the running picture at all, unless a large quantity
of film is cut out. If however, the splice be made over part of a
picture--as would be the case if an improper number of holes were cut
out--the picture, when projected, would appear out of frame, i.e., the
dividing line between two pictures would then appear on the screen and
would continue to show until the framing lever had been adjusted to
cover the dividing lines again. Care must also be taken that the film is
straight after being spliced. If the ends are not fitted squarely to
each other, there will be a bend in the film at the point the splice is
made; and this may cause trouble.
Many operators have a plate of ground glass fitted into a work bench at
the place where splices are to be made and a small lamp under this
glass. This is very convenient for, as a rule, the illumination in an
operating room is very poor although a good light is necessary to match
film properly. If ground glass is used, the rough side must be at the
bottom; otherwise it will be difficult to clean off the cement which
adheres to the glass.
By making every splice in exactly the same order, the operator will
acquire the habit of doing it nicely and quickly. Most splices are made
in a hurry (before or after a show) and in this, as well as in all
things that must be done hastily and at a moment’s notice, habit and
practice are very important. One does not become expert until he has
practiced it often enough to be able to do it mechanically.
[Illustration: FIGURE 51.]
Proceed as follows and as outlined in Figure 51: Cut exactly along the
dividing line of one picture and save this to become the top piece. (The
emulsion side of the two sections of film must always be either up or
down, and for convenience it is well to form the habit of having them
always one way or the other.) Now, with a sharp knife, scrape the
celluloid side of this piece until all of the gloss is removed for a
width of a little more than 3/16 inch. Do not scrape any more than
necessary, but be sure that all dirt and oil are removed. Now take up
the other part of the film and cut off the bad portion, leaving a strip
a trifle less than 3/16 inch beyond the dividing line. This strip need
not be scraped on the back, but all of the emulsion must be scraped from
the front side of it. To scrape the front side nicely, lay a short ruler
across it to act as a guide for the knife and scrape up to this ruler.
Scrape only to the dividing line, but give particular attention to the
sprocket holes and the edges, for it is at the edges and sprocket holes
that film first begins to work loose and where it is most difficult to
secure proper adhesion. Both parts of the film should be so scraped
that, when finished, each will furnish half of the dividing line. Now
apply a liberal coating of cement to the latter section and carefully
lay the first upon it, taking great care that the sprocket holes in the
two sections overlap and match perfectly. It is for this matching
purpose that the glass in the table (with a small lamp underneath it)
is valuable. The sprocket holes must match accurately and the films must
line up straight. After the upper film is placed, it must be pressed
down for a few seconds until the cement has set. Wipe off all
superfluous cement before it has time to set. Be sure that there are
four sprocket holes for each picture. Keep a knife on hand and use it
for no other purpose. Keep also a suitable stone on which to sharpen
this knife, for, unless the knife is very sharp, it will do only poor
work and the edge on it will not last long at any rate. Ordinary cement
will not hold non-inflammable film, and water-proof film must be more
thoroughly scraped than ordinary film. In the bench, provide a recess
into which the cement vessel may be set and where it will always remain.
Provide also a pair of scissors for cutting the film.
[Illustration: FIGURE 52.]
The Edison film mender is shown in Figure 52. This is made with three
gates or hinges. Those on the right and left clamp down to hold the
film, while the narrower one in the center clamps down on the cemented
edge. To mend a film, place one of the pieces to be joined in the
mender. Place that part of the gage marked “cut” in position, cutting
between first and second perforations above the floor line separating
the picture. The remaining piece of film should be placed in the other
side of the mender and cut exactly on the line. Set the opposite end of
the gage marked “scrape” on the first section; remove the emulsion; cut
to the floor line with a sharp pen knife, moistening it so that the
emulsion will come off easily. After applying the cement with a brush to
the scraped piece, lay the other piece over it in the mender, clamping
it down; and leave it for an instant to adhere.