Chapter One: CamerasThe cinematographer's most basic tool is the motion picture camera. This piece of precision machinery comprises scores of coordinated functions, each of which demands understanding and care if the camera is to produce the best and most consistent results. The beginning cinematographer's goal should be to become thoroughly familiar and comfortable with the camera's operation, so that he or she can concentrate on the more creative aspects of cinematography.
This chapter covers many isolated bits of practical information. However, once you become familiar with camera operation, you will be able to move on to the substance of the cinematographer's craft in subsequent chapters. In the meantime, you are well advised to try to absorb each operation-oriented detail presented in this chapter, because operating a camera is all details. If any detail is neglected, the quality of the work may be impaired.
Principle of Intermittent MovementThe film movement mechanism is what really distinguishes a cinema camera from a still camera. The illusion of image motion is created by a rapid succession of still photographs. To arrest every frame for the time of exposure, the principle of an intermittent mechanism was borrowed from clocks and sewing machines. Almost all general-purpose motion picture cameras employ the intermittent principle.
Intermittent mechanisms vary in design. All have a pull-down claw and pressure plate. Some have a registration pin as well. The pull-down claw engages the film perforation and moves the film down one frame. It then disengages and goes back up to pull down the next frame. While the claw is disengaged, the pressure plate holds the film steady for the period of exposure. Some cameras have a registration pin that enters the film perforation for extra steadiness while the exposure is made.
Whatever mechanism is employed requires the best materials and machining possible, which is one reason good cameras are expensive. The film gate (the part of the camera where the pressure plate, pull-down claw, and registration pin engage the film) needs a good deal of attention during cleaning and threading. The film gate is never too clean. This is the area where the exposure takes place, so any particles of dirt or hair will show on the exposed film and perhaps scratch it. In addition to miscellaneous debris such as sand, hair, and dust, sometimes a small amount of emulsion comes off the passing film and collects in the gate. It must be removed. This point is essential. On feature films, some camera assistants clean the gate after every shot. They know that one grain of sand or bit of emulsion can ruin a day's work.
The gate should first be cleaned with a rubber-bulb syringe or compressed air to blow foreign particles away. Cans of compressed air must be used in an upright position; otherwise they will spray a gluey substance into the camera. When blowing out the aperture, it is recommended that you spray from the open lens port side, with the mirror shutter cleared out of the way, through the aperture, rather than from inside the threading area into the aperture. This helps prevent blowing particles into the mirror area. An orangewood stick, available wherever cosmetics are sold, can then be used to remove any sticky emulsion buildup. There is also an ARRI plastic "skewer" for this job, bent at the end to allow you to get the inner edges of the aperture better. The gate and pressure plate should also be wiped with a clean chamois cloth -- never with linen. Never use metal tools for cleaning the gate, or, for that matter, for cleaning any part of the film movement mechanism, because these may cause abrasions that in turn will scratch the passing film. Do not use Q-tips either, as these will leave lint behind.
The gate should be cleaned every time the camera is reloaded. At the same time, the surrounding camera interior and magazine should also be cleaned to ensure that no dirt will find its way to the gate while the camera is running.
The intermittent movement requires the film to be slack so that as it alternately stops and jerks ahead in one-frame advances, there will be no strain on it. Therefore, one or two sprocket rollers are provided to maintain two loops, one before and one after the gate. In some cameras (such as the Bolex and Canon Scoopic), a self-threading mechanism forms the loops automatically. In Super-8 cassettes and cartridges, the loops are already formed by the manufacturer. On manually threaded cameras, the film path showing loop size is usually marked.
Too small a loop will not absorb the jerks of the intermittent movement, resulting in picture unsteadiness, scratched film, broken perforations, and possibly a camera jam. An oversize loop may vibrate against the camera interior and also cause an unsteady picture and scratched film. Either too large or too small a loop will also contribute to camera noise.
Camera Speeds
The speed at which the intermittent movement advances the film is expressed in frames per second (fps). Each frame exposed is a single sample of a moving subject, so the higher the sampling rate, that is, the faster the frame rate, the smoother the motion will be reproduced. To reproduce movement on the screen faithfully, the film must be projected at the same speed as it was shot. Standard shooting and projection speed for 16mm and 35mm is 24 fps; standard speeds for 8mm and Super-8 are 24 fps for sound and 18 fps (or 24 fps) for silent.
If both the camera and the projector are run at the same speeds, say 24 fps, then the action will be faithfully reproduced. However, if the camera runs slower than the projector, the action will appear to move faster on the screen than it did in real life. For example, an action takes place in four seconds (real time) and it is photographed at 12 fps. That means that the four seconds of action is recorded over forty-eight frames. If it is now projected at standard sound speed of 24 fps, it will take only two seconds to project. Therefore, the action that took four seconds in real life is sped up to two seconds on the screen because the camera ran slower than the projector.
The opposite is also true. If the camera runs faster than the projector, the action will be slowed down in projection. So to obtain slow motion, speed the camera up; to obtain fast motion, slow the camera down.
This variable speed principle has several applications. Time-lapse photography can compress time and make very slow movement visible, such as the growth of a flower or the movement of clouds across the sky. Photographing slow-moving clouds at a rate of, say, one frame every three seconds will make them appear to be rushing through the screen when the film is projected at 24 fps. On the other hand, movements filmed at 36 fps or faster acquire a slow, dreamy quality at 24 fps on the screen. Such effects can be used to create a mood or analyze a movement. A very practical use of slow motion is to smooth out a jerky camera movement such as a rough traveling shot. The jolts are less prominent in slow motion.
To protect the intermittent movement, never run the camera at high speeds when it is not loaded.
When sound movies arrived in 1927, 24 fps was firmly established as the standard shooting and projection rate, although it was a frame rate occasionally used by Silent Era filmmakers. It is not actually the ideal frame rate for the recreation of motion, as it provides barely enough individual motion samples over time to create the sensation of smooth, continuous motion when played back. However, it's become the frame rate that audiences are most accustomed to seeing in movies and has become an integral part of the "film look" that many people discuss these days as they attempt to get video technology to emulate film. The main artifacts to this fairly low frame rate are strobing and flicker. Strobing is the effect of sensing that the motion is made up of too few samples and therefore does not feel continuous. One of the ramifications is that it is sometimes necessary to minimize fast movement, such as when panning the camera across a landscape; otherwise the motion seems too staccato, too jumpy. Flicker happens when the series of still images are not being flashed quickly enough for the viewer to perceive the light and image as being continuously "on." The solution generally has been for film projectors to use a twin-bladed shutter to double the number of times the same film frame is flashed before the next frame is shown. So even if the movie was shot and then projected at 24 fps, the viewer is seeing forty-eight flashes per second on the screen.
ShutterA change in camera speed will cause a change in shutter speed. In most cameras the shutter consists of a rotating disk with a 180* cutout (a half circle). As the disk rotates it closes over the aperture, stopping exposure and allowing the movement to advance the film to the next frame. Rotating further, the cutout portion allows the new frame to be exposed and then covers it again for the next pull-down. The shutter rotates constantly, and therefore the film is exposed half the time and covered the other half. So when the camera is running at 24 fps, the actual period of exposure for each frame is 1/48 second (half of 1/24). Varying the speed of the camera also changes the exposure time. For example, by slowing the movement by half, or to 12 fps, we increase the exposure period for each frame, from 1/48 to 1/24 second. Similarly, by speeding up the movement, doubling it from the normal 24 fps to 48 fps, we reduce the exposure period from 1/48 to 1/96 second. Knowing these relationships, we can adjust the f-stop to compensate for the change in exposure time when filming fast or slow motion.
A change in the speed of film movement can be useful when filming at low light levels. For example, suppose you are filming a cityscape at dusk and there is not enough light. By reducing your speed to 12 fps, you can double the exposure period for each frame, giving you an extra stop of light that may save your shot. Of course, this technique would be unacceptable if there were any pedestrians or moving cars in view; they would be unnaturally sped up if the film were projected.
Some cameras are equipped with a variable shutter. By varying the angle of the cutout we can regulate the exposure. For example, a 90° shutter opening transmits half as much light as a 180° opening. Some amateurs make fade-outs and fade-ins on their original film by using the variable shutter, assuming it can be changed smoothly while the camera is running. Professionals generally have all such effects done in the lab.
Since changing the camera speed also changes the exposure, you can compensate for a speed change in midshot (called speed ramping) by adjusting either the f-stop or the shutter to maintain the correct exposure. For example, a speed change from 24 fps to 12 fps would cause twice as much light to reach the film by the time it was running at 12 fps, so you could simultaneously close down the shutter angle from 180° to 90° as the frame changes, thus counteracting the exposure increase. However, the rendition of motion will be different when you alter the shutter angle, not just when you alter the frame rates.
Shutter movement is directly responsible for the stroboscopic effect. Take the example of the spokes of a turning wheel. Our intermittent exposures may catch each succeeding spoke in the same place in the frame, making the spinning wheel appear to be motionless. The camera may even catch each spoke in a position counterclockwise to the previous spoke captured, making the wheel look like it is running in reverse. Another variation, called skipping, results from movement past parallel lines or objects, such as the railings of a fence. They may appear to be vibrating. These effects will increase with faster movement and with a narrower shutter angle.
Exposure time controls the amount of motion blur recorded on each frame; due to the low sampling rate of 24 fps, a certain amount of blur is needed to make a moving object on one frame visually "blend" with the next frame. Too little blur and the motion seems too "sharp" and the viewer becomes more aware as to how few motion samples there really are; it no longer feels continuous but instead "steppy." Therefore, shooting at 24 fps with a closed-down shutter, like at a 45° or 90° angle, will cause faster motion to strobe heavily. This has been used as a creative effect by some filmmakers, since it adds a certain nervous, jittery energy to action scenes. The movie Saving Private Ryan is the most famous example of this technique; many of the battle scenes were shot handheld with a 45° shutter angle. It's also a useful technique when shooting spraying water or falling rain, if you want to see each droplet more clearly.
There are other reasons to use a shutter angle other than 180°, such as for filming TV screens or lights that pulse with their AC current. (See chapter 8.)
Viewing SystemsIn many cameras the shutter performs a vital role in the viewing system. The front of the shutter has a mirror surface that reflects the image into the viewfinder when the shutter is closed. The great advantage of this reflex system is that all the light goes alternately to the film and to the camera operator's eye, providing the brightest image possible. The surface of the mirror shutter should be cleaned only with an air syringe or gently with compressed air; nothing should be allowed to touch it.
Other systems (such as the Bolex Reflex) use a prism between the lens and the shutter so that a certain percentage of the light is constantly diverted to the viewfinder. The disadvantage is that it reduces the amount of light going both to the viewfinder and to the film, since the beam is split. An exposure compensation is required to allow for the light "stolen" from the film by the viewing system. It is usually very slight. For example, in the Bolex Rex-5 the loss is about a third of a stop. You should consult the operator's manual for the specific camera to learn the exact compensation.
Be aware that just as the reflex camera allows light coming through the lens to reach both the film and the camera operator, it also allows light coming back through the eyepiece to reach the film. Therefore, you must keep your eye pressed against the viewfinder while filming to prevent any light-leak from fogging your image; if you are not planning on looking through the viewfinder during the take, you must seal off the eyepiece.
The viewing systems discussed so far allow the cameraperson to look through the taking lens. Many cameras of older design do not have a reflex viewfinding system. As a result, the film in the camera may not receive exactly the same image that the separate viewfinder (usually off to one side of the camera) sees. Referred to as parallax, this is especially a problem when shooting close with a wide-angle lens. However, most nonreflex cameras have an adjustment that can partly correct for parallax.
Video Assist
Also referred to as a video tap, this is a system where some of the light going to the viewfinder is also received by a tiny internal video camera; that image can then be sent to a TV monitor, either with cables or transmitted by UHF (by using an additional device). This signal can even be recorded to videotape for temporary playback on the set. The image quality of this video image is generally very poor, but it allows you to see the framing without actually looking through the viewfinder. This is mainly done so that people other than the camera operator can see the exact shot during the take. However, it is also useful when it is physically impossible to look through the camera viewfinder during the take, like when the camera is mounted on a moving vehicle, a Steadicam, or a remote-controlled crane. Occasionally the camera assistant will have a small LCD monitor mounted to the camera, which enables the assistant to see what the operator is framing. This can come in handy when shooting a scene on a telephoto or macro lens in which the operator is panning from one object to another and the focus needs to be adjusted as each object comes into view. The portable LCD screen can even be used by the operator when doing a complex dolly move, perhaps with an extreme boom up or down combined with a pan, when it may be too difficult to continually keep the eye against the viewfinder.
MotorsThe film transport mechanism, the shutter, and other moving camera parts are operated by the motor. There are two basic types of motors, spring-wound and electric. Spring-wound cameras run approximately twenty to forty feet of film per wind. The advantages include a compact design and reliable performance under difficult conditions such as cold weather.
Electric motors are available in a variety of designs. The five types that are generally used are: (1) variable speed ("wild"); (2) interlocked; (3) stop frame (time-lapse); (4) constant speed; and (5) crystal speed, which is the most commonly used, especially for sync-sound production. Variable speed motors have an adjustable speed control that may range from 2 to 64 fps or more. (Above 64 fps are considered high-speed motors.) The interlocked motor synchronizes the camera with other devices, such as back or front projectors. The stop frame or time-lapse motor is usually connected with an intervalometer to allow the setting up of whatever exposure intervals are needed for time-lapse photography (such as filming the growth of plants). The constant speed motor is designed to run at a set speed, such as 24 fps, with some precision.
The most advanced type of synchronous speed motor is designed with a crystal control to regulate the speed with extreme precision. When the camera motor and the tape recorder are both equipped with crystal controls, you can film "in sync" with no cables connecting the camera to the recorder. Furthermore, several crystal control cameras can be held in sync to one or more crystal recorders, allowing for multicamera coverage with no cables to restrict the distances between them. Some crystal control motors even combine several functions, allowing the operator to change from constant speed crystal-sync to variable "wild" speeds or single frame at the touch of a switch. The best controls allow a wide variety of speeds to be shot precisely at crystal-sync, necessary for filming under certain pulsing AC light sources at high frame rates for a slow-motion shot.
BatteriesMost 16mm camera motors operate on DC current supplied by batteries. Nickel-cadmium (NiCad) and nickel metal hydride (NiMH) are widely used; lithium ion batteries are becoming more common. Their life expectancy varies, depending on the conditions of use and maintenance, but on the average about five hundred cycles of recharging and discharging should be expected.
There are slow "overnight" chargers that require fourteen to sixteen hours, quick chargers that will charge batteries in half this time, and truly fast chargers that can do the job in one hour.
It is essential to familiarize yourself with the charger on hand. Some chargers will damage a battery when left to charge for longer than required. It is advisable to have at least four charged batteries on hand so that they can be rotated with enough time for slow charging.
Batteries come in three types: belt, block, and on-board. The battery belt, consisting of built-in nickel-cadmium cells, is a convenient power source for portable 16mm and 35mm cameras, especially when shooting handheld. In situations where mobility is less of an issue, longer-lasting but heavier block batteries may be used. Many modern 16mm cameras use small on-board batteries that clip onto the rear or side of the camera. All Super-8 cameras house the batteries (usually AAs) inside the camera body.
Make sure the voltage of the battery used matches what your camera motor uses. The 16mm Arri SR1 and SR2, and the Aaton XTRprod and A-Minima, for example, use a 12-volt battery, but the Arri SR3 uses a 24-volt battery (as do many 35mm cameras). Many battery belts and block batteries can be switched between 12V and 24V, or between 12V and 16V. Plug into the correct voltage connector on these batteries.
MagazinesMost of the smaller 16mm cameras will house up to 100-foot loads (on metal daylight spools) inside the camera body. Modern 16mm cameras are usually equipped with film magazines capable of holding up to four hundred feet of film on a plastic core instead of a metal spool. Four hundred feet of film stock in a camera running at 24 fps will give you eleven minutes of footage. The Aaton A-Minima uses a unique 200-foot plastic spool design that must be loaded in darkness. There is an optional 1,200-foot magazine for the 16mm Panaflex Elaine and an 800-foot magazine made for the Aaton XTRprod and Arri SR3 cameras.
Having several magazines allows for a more efficient production, particularly when more than one type of film stock is used on a given day. The camera assistant loads several magazines in advance so that the magazine change will slow down the production minimally.
Remember, when considering magazines, the two decisive factors are capacity and design. The shape and placement of the magazine is sometimes important too. For most shooting situations it doesn't matter, but when you are shooting in cramped quarters, such as from the cockpit of a plane or from under a car, the bulkiness of the camera can make a difference. Here a cameraperson may want a camera with magazines that are smaller or that mount to the back rather than the top. The operator may even want to use one of the smaller cameras that only allow the 100-foot daylight spool loads.
Most magazines have to be loaded in total darkness. The smaller loads available on daylight spools require only subdued light when loading; however, these are not generally used in modern sync-sound cameras, as they increase the noise level while the camera is running. Film not on daylight spools necessitates either a darkroom or a changing bag. The changing bag must be of adequate size and absolutely light-tight. It should be stored in a special case or cover to keep it spotlessly clean and dust free. (Don't let your dog sleep on it.) Any hairs, dirt, or dust in the changing bag can easily enter the magazine being loaded and from there travel to the gate. Even the tiniest of dust specks are visible on a 16mm frame because of the higher magnification of the image.
Before loading an unfamiliar magazine, practice loading it with a roll of waste film (called a dummy load) that you don't want, first in the light and then in the dark, to simulate the loading of unexposed stock.
Some magazines have their own take-up motors to wind up the film as it reenters the magazine after passing through the camera. Such motors should be tested with a waste roll before the magazine is loaded with unexposed film. Run this test with the battery to be used in filming. This test is advisable because a battery may sometimes have enough charge to run a camera with a small 100-foot internal load or an empty magazine but then fail to operate the magazine and camera when it is loaded.
Also, before loading, clean the magazine with compressed air, camera brush, and a piece of sticky paper in order to remove dust, film chips, or hair, and make sure that the rollers are moving freely. (Never wear a fuzzy or hairy sweater when cleaning camera equipment or in the darkroom.) It is a good idea to do a scratch test where you run some new film through the camera to see if the magazine or the gate is scratching the film. You examine the strip of film afterward with a light and magnifier to look for any faint abrasions in the surface of the emulsion or base. Obviously this piece of film becomes waste at this point, having been exposed to light.
After loading the magazine it is advisable to seal the lid with 1-inch camera tape. This is partly to prevent light leakage on old magazines, but mainly to prevent an accidental opening, especially if the loaded magazine is dropped. When you are loading magazines in a hurry, it is easy to confuse loaded ones and unloaded ones. Taping and labeling the loaded magazines immediately after loading will save you the annoyance of opening a supposedly empty magazine and ruining a roll of film.
It is customary to stick a piece of 1-inch white tape on the side of the magazine with the following information:
- number of that magazine
- camera roll number
- type of film stock
- emulsion and batch number
- length of the roll
- date
- title of the film
- name of the production company
This will help in the preparation of a camera report to accompany the film to the lab. Later this label is often taken right off the magazine and put onto the film can holding the exposed roll. You might also put a label on the magazine with special processing instructions, such as PUSH ONE STOP, as a reminder to everyone using the camera and to whoever later writes the camera reports and work order for the lab.
Despite the most careful cleaning and loading, even the finest camera designs will occasionally jam. The film will stop advancing somewhere along its path and the oncoming film will continue to pile up at that point, creating a "salad" of twisted and folded film. If the camera jams, remove the film from the camera interior, checking carefully to see that chips of broken film are not stuck in the gate, around the registration pin, or anywhere else. Remove the magazine to a darkroom or put it in a changing bag. You will need a spare take-up core or spool (whichever you already have in the camera) and a can with a black paper bag to unload the exposed film and rethread the magazine.
Never spool up any film with broken sprocket holes. It may jam in the processing machine in the lab and ruin a considerable amount of footage, not only yours but other customers' as well. Generally you would feel the edge of the film in the dark and snip off the part of the roll where the perforations have been broken. If you can't find the torn perf but suspect any damage inside your roll of film, write a warning clearly on the can to alert the lab technicians.
One simple procedure that helps prevent camera jams is to make sure there is no slack between the take-up roll and the sprocket roller. If there is, when the camera starts the take-up motor may snap the film taut, breaking it or causing the camera to "lose its loop" and become improperly threaded. There is usually some way of rotating the take-up roll to make it taut before you start to shoot. On the Arri SR cameras, for example, there is a button labeled "Test" that you are supposed to hit whenever you load a new magazine onto the camera. It gently engages the claw into a sprocket hole so that when you run the camera, you won't immediately damage a perf. On other cameras, you may want to manually inch the film through the movement to make sure that the loops are the correct size and that the claw is properly engaging the sprocket hole before you then trigger the camera motor.
Some magazines, instead of using a plastic core to take up the exposed film, use a metal collapsible core. Be sure not to send the roll to the lab with the collapsible core still in the center. When unloading a magazine, unclasp the collapsible core and gently lift up the roll with one hand on the inner edge and one on the outer edge. Do not let the center of the roll drop, which is called "coning" the roll and is very tedious to fix: you'd have to rewind the roll by hand in total darkness. Some magazines also have a center part that covers the spindle but holds the plastic core. Don't pull this center piece off and send it to the lab along with your film. This is very important. If you send this costly little piece to the lab, you will have trouble trying to reload the magazine without it.
Super-8 film comes in cartridges and cassettes. Not much can be done if a cassette jams, but you can help prevent jamming by making sure the cassette fits easily into the camera.
LensesBeginners in filmmaking are quite often confused by the various aspects of camera lenses. They are intimidated by the mathematical formulas that appear in many photography books whenever lenses are under discussion. But today the filmmaker's life is easier. Readily available tables provide all the information that previously required mathematical computation. Common sense is all you need to understand lenses.
The basic function of a lens can be explained as a pinhole phenomenon. If you removed the lens from your camera and replaced it with a piece of black cardboard with a pinhole in it, you could take a picture, provided the exposure time was long enough. The picture on film would be upside down and the sides would be reversed. This is the first thing one should know about lenses: they produce images that are reversed both vertically and horizontally. The advantage of the lens over the pinhole is that while a pinhole allows only a very small amount of light to reach the film, the lens collects more light and projects it onto the film. In this way, shorter exposure times and sharper pictures are achieved.
F-stops and T-stops
The maximum amount of light a lens is capable of transmitting depends on the diameter of the lens and the focal length. By focal length we mean the distance from the optical center of the lens to the film plane when the lens is focused at infinity. The focal length divided by the diameter of the lens gives us a measure of the maximum aperture. It's quite simple. For example, a lens 1 inch in diameter with a focal length of 2 inches will pass the same amount of light as a lens 3 inches in diameter with a 6-inch focal length, because the maximum aperture, or f-stop, for both lenses is f/2 (2 4 1 5 2; and 6 4 3 5 2 also).
We can reduce the amount of light by means of an iris placed in the lens. By closing the iris we reduce the effective diameter of the lens, thus reducing the amount of light passing through the lens. Now the f-stop equals the focal length divided by the new diameter created by the iris. Therefore, if a 2-inch focal-length lens has an iris adjusted to a 1/8-inch opening, the f-stop is f/16, because 2 4 1/8 5 16. A 4-inch lens with a 1/4-inch iris opening would also be f/16, because 4 4 1/4 5 16.
So the f-stop calibration is not merely a measure of the iris opening, but instead expresses the relationship between focal length and iris.
It is important to note that the smaller the iris opening, the more times it can be divided into the focal length. Therefore, as the iris opening becomes smaller, the f-stop number becomes higher. So a lower f-stop number means more light (a larger opening), and a higher f-stop number means less light (a smaller opening).
F-stops are calibrated on the lens. They are commonly 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, and 22. Each higher f-stop cuts the light by exactly half. For example, f/11 allows half as much light as f/8. Conversely,