How Filmmaking Cameras Work
Movies don't move. A movie is a series of still pictures presented to the viewer so rapidly that the viewer's brain is fooled into thinking the images are moving. The eye holds the image of one picture for a moment after it is no longer shown until the next picture appears. This is called persistence of vision and allows movies to work.
Movies consist of 24 separate still photographs projected each second. This is just fast enough to generally convince the eye that the images are alive and moving.
Cameras use a lens to focus the light rays coming from the scene onto a small rectangular area of film or, in the case of video, onto an electronic circuit that is sensitive to light. In a film camera a shutter opens allowing light to shine on the film for a moment, then the shutter closes and the film is advanced to the next frame by a claw mechanism. Then the process repeats 1/24th of a second later. In a video camera light is gather by the electronic circuit for a fraction of a second then the brightness and color values are read out of the circuit for processing and writing to some form of memory.
Film consists of light sensitive chemicals coated on a thin, clear cellulose acetate or other flexible plastic film. The chemicals are color dyes and silver compounds (explaining the high cost of photographic film). Most high-budget, professional films are still shot on 35mm color film stock. 35mm film has been the common format since the very first movies.
When the film is processed it becomes a negative image of the original scene with the lightest areas of the original scene represented as black on the film, and the darkest areas of the scene staying light and transparent on the film. Colors are also reversed. A positive print has to be made from the negative in order to view the film correctly.
16mm is a lower cost alternative but somewhat lower quality. A few filmmakers experiment with super-8mm but the results don't hold up well in theater projection. All the world's theater projectors are 35mm so any other film size will have to be enlarged and reprinted onto 35mm at some point if it is to be shown in theaters.
Film can be shot in a variety of rectangular shapes called aspect ratios. A movie's aspect ratio is given as a ratio of the width of the frame divided by the height. The classic size of 35mm film and standard definition television is a width of 4 units and a height of 3 units giving an aspect ratio of 1.33:1. This aspect ratio is often referred to as Academy aperture after the Academy of Motion Picture Arts and Sciences which first defined and standardized it.
Although the Academy frame was standard for most of the early years of filmmaking a wider aspect ratio is now preferred. In America the most common ratio is a 1.85:1 widescreen ratio. Most European films are shot with a 1.66:1 ratio making them not quite as wide as American films project for the same height. The film is shot on the same 35mm film stock but the top and bottom of each frame is cropped by masking it off in the cameras and projectors. High definition video uses an aspect ratio of 16 to 9 units, or 1.78:1 which is very close to 1.85:1 widescreenand makes a transfer to film possible with only a small amount of cropping.
Another popular format is anamorphic widescreen having an aspect ratio of 2.35:1. It is sometimes referred to as scope after the trade name Cinemascope. Scope is also shot on the same 35mm stock and the extra wide aspect ratio is achieved by a combination of cropping the top and bottom of the frame and using a special anamorphic lenses which images the scene onto the film by squeezing the image more horizontally than vertically.
35mm cameras are generally very large, heavy and cumbersome pieces of equipment. They require substantial tripods and dollies and several operators to use them. Some newer cameras are small and light enough to be handheld or supported on a Steadicam, a support that is attached to an operator and keeps the camera steady while the operator walks through the scene.
35mm production is worth it when the budget is large enough as non of the current video formats can quite equal the quality.
A few productions are even shot using special 65mm or 70mm film and cameras. Films such as Lawrence of Arabia and the popular IMAX films have startlingly rich and detailed images.
Most film cameras do not record sound along with the image. The sound is recorded in a double system where a separate sound recorder captures the sound from the microphones which is later matched to the film during the editing process. For a long time sound was recorded on Nagra analog tape recorders. DAT (digital audiotape) recorders replaced them with their perfect speed and superior sound. Hard disk recorders and even direct to memory card recorders have pretty much taken over professional productions today. These recorders are essentially portable computers dedicated to recording sound.
Film cameras designed for making sound films have synchronizing crystal clock circuitry to keep the film moving at a precise speed and in perfect sync with the sound recording.
Much of the sound you hear in films today is actually recorded after the fact in a studio. Sound effects, music and even dialog are recorded and added long after the filming is completed.
Traditional film editing is a very mechanical process involving physically cutting and splicing a copy print of the master negative to sequence together the scenes of the movie. Each day's film is processed and printed onto positive film stock and shown to the director as dailies or rushes. Sound is transferred from the original media to 35mm magnetic sound stock to be matched to the image film.
When all the sequencing of scenes is done the same cuts are applied to the original master negative in a process called negative matching or conforming. Dissolves between scenes and color correction (called color timing) is done after the editing is finished by optical processes.
When the sequencing and color correction is done a sound mix (or rerecording) is done to get the final sound and it is all put together to create an answer print Necessary changes are communicated back to the laboratory from the director and editor. Eventually a release print is produced and the film is ready for distribution and theater screenings.
In the 1990s this process began to change as directors chose to capture images from the master negative into digital images in a computer and perform nonlinear editing of the digital images in a computer. When the edit is done the digital images are put back onto film stock for distribution. The process costs more but may make the edit go faster and usually results in a better quality film.
Video cameras, like film cameras, focus light to capture a series of still images giving the illusion of motion. They capture light onto a light sensitive computer chip, usually a CCD (charge-coupled device), instead of film. Unlike film which has a relatively continuous light sensitive surface, the computer chips records the scene as a matrix of individual colored spots called pixels. The number of pixels a video camera can capture limits the resolution of the final images. The resulting digital images are usually stored onto magnetic tape, or in some of the latest cameras, onto memory cards.
For the purposes of modern filmmaking one can eliminate all the older analog forms of video such as VHS, 8MM and Hi8 because they produce much lower quality images for about the same cost as digital video formats.
Standard definition (SD) video, such as mini DV, is not a good choice for making a production intended to viewing in a theater for several reasons. SD video is effectively limited to about 1/4 of a megapixel of resolution, or about 250,000 pixels so the images have poor detail when blown up to the size of a theater screen. The aspect ratio in most cameras is 1.33:1 rather than widescreen. SD also has a frame rate of approximately 30 frames per second rather than 24.
To make matters even worse the frames are divided into two interlaced frames every 1/60th of a second. The odd horizontal rows of pixels are made into a picture, then 1/60th of a second later the even horizontal rows of pixels are made into another picture. The two frames can't be combined because any movement in the frame results in two slightly different views so the moving objects seem to have fine comb-like edges. Very clever software is required to convert 30 frame per second interlaced video into single images every 1/24th of a second.
High definition (HD) video formats get around many of the issues with SD video. First the resolution is much greater with HD's resolutions of either 1 megapixel per frame or 2 megapixels per frame. Compression techniques reduce this resolution somewhat with many HD recording systems but HD is still startlingly sharper than SD.
Many HD cameras can record at 24 frames per second. A few can even record at a variety of frame rates making fast and slow motion filming possible. Some HD cameras also record entire frames at a time, know as progressive filming, eliminating the problem of interlaced images.
Unlike professional film cameras nearly all video cameras have the ability to record muti-track, DAT quality sound onto the same tape as the images, and in perfect sync. This greatly simplifies the production and editing processes of video filmmaking compared to film production.
There are three big caveats the beginning filmmaker needs to be aware of. First is that most amateur level video cameras have very low quality sound pre-amplifiers which means that the sound captured is 48khz, 16-bit stereo just like DAT, but will probably have hiss and distortion that would not by added by a professional level video camera.
Second is that most amateur level video cameras only offer automatic gain control. This means the camera is constantly trying to adjust the volume of sound capture based on how loud the sound is, resulting in possible distortion due to sudden loud noises and picking up too much background noise when there is little other sound to pick up. Professional production requires being able to set a sound level for capture and keep it constant.
Third is that the microphone built into the camera, even the most expensive professional camera, will not get good enough sound for filmmaking. The reason is simply that the built-in microphone will be too far from the actors to register the sound clearly without also picking up an excess of room noise and reverberation. Such poor sound quality is often the most obvious sign of a really amateur production. It doesn't work. You must have a separate, quality microphone that you can get as close as possible to the actors.
Video editing is easily done on relatively inexpensive personal computers. Digital non-linear editing allows the editor to experiment far beyond what what was ever possible with film editing, and the ability to apply digital enhancements goes far beyond what was possible even a decade ago, at any cost. Digital video editing will be covered more thoroughly in the postproduction section.
Film vs. Video, Video vs. Film
Not long ago an independent filmmaker working on a very small budget would shoot 16mm black & white film. The cost savings were significant over 35mm color film. Black & white film is actually more expensive than color film anymore so that isn't an option for saving money.
Today the choices of image capture technology are broader than ever but is it really any cheaper to shoot on video rather than film?
The quick answer is: No. Equivalent camera packages cost about the same amount to rent whether video or film. You will need the same number of crew members and the same selection of lights, microphones, etc. With film you will pay $50,000 for film and processing up front. With video the tape is cheap but someone has to pay $50,000 to get the film transferred to 35mm film before the movie can be shown in commercial theaters. In the end you've paid the same amount for an equivalent production.
Still, there are some important differences. Factors that favor video include:
- The least expensive video cameras that can give you an acceptable image for making a movie is a lot less expensive than any 35mm camera.
- Capturing sound in sync with a video camcorder is an advantage over the separate capture and post production syncing necessary with film.
- The smallest video cameras can get into places a film camera won't fit.
- Video cameras can shoot 40 to 60 minutes or more on a single tape without interruption compared to about 10 minutes maximum for film. This allows the actors to work longer on their performance, do longer and uninterrupted takes and not worry as much about mistakes.
- As soon as you yell "cut" you can review your shot. No film processing step. Editing can start at once without the expense of transferring from film to tape.
- The lowest possible budget video production will cost a lot less than the lowest budget 35mm shoot.
- You can defer the cost of transferring the video to film until your movie has been sold. If you end up going directly to DVD or cable then you don't have to pay to transfer to film.
Factors that favor film include:
- Film is more tolerant of wide difference in the brightness of light in a scene therefore can be easier to light. Video usually requires more careful lighting to achieve the same effect.
- Film is capable of resolving more detail than any commonly available video format, approximating an 8 megapixel digital image. HD is at best about 1 to 2 megapixels depending on format. However by the time 35mm film has gone through all the processing and optical copying steps necessary to get it to the theater its resolution is not much better than 2 megapixels.
- 35mm film give less depth of field compared to video cameras which allows greater control of what the audience focuses on.
- Unless video is captured in an uncompressed format, which is very expensive and technically challenging, compression artifacts and loss of color detail can become obvious compared to 35mm film.
- Most D.P.s are used to working with film so the techniques are well understood and the work flow is well worked out. Video workflows are still evolving so the crew is having to learn as they go.
- Film has a "look", because of the grain, non-linear gamma and other subtle factors, that create an appearance and texture in the images that audiences associate with movies.
The bottom line is that if you really want the look of film and your D.P. wants to shoot on film then find a way to shoot 35mm film. If there is a look you can achieve only with video, portability is a factor, you need to defer as many costs as possible, you are going directly to DVD, you are doing a documentary and must shoot hundred of hours of images or you just have no money but want to make a movie then shoot on video.
One is not better than the other. They are just different.
HDV seems to be the sweet spot for low-budget filmmakers at the moment. There are a handful of "pro" models that are especially interesting. Although they don't all use true HDV technology they all use a form of High Definition recording that will deliver a detailed image the equal of traditional 16mm film or better onto the big screen if properly handled.
- Canon XL H1 It's Superior Canon Optics and exceptional image processing give you a brilliant HD image. The XL H1 also features uncompressed HD-SDI (SMPTE 292M) and SD-SDI (SMPTE 259M) output, as well as Genlock input and SMPTE time code input and output for multi-camera shoots. The XL H1 features total Cine control, customizable settings and a well-balanced design for the creative control, flexibility and advanced capability your video work demands. The XL H1 is starting to ship for USD$9,000.
- Panasonic AG-HVX200 is the much anticipated replacement for the DVX-100. It supports recording the video directly to P2 solid-state memory cards. HD and SD video is recorded on the P2 card as IT-friendly MXF files that can be downloaded to a nonlinear editing system or server, or edited virtually instantly from the P2 card by connecting an IEEE 1394 or USB2.0 interface. P2 cards mount like a regular hard drive from a NLE system's point of view, which eliminates the time-taking task of digitizing footage. The AG-HVX200 is not an HDV camera. Panasonic has decided to go with their own DVCPRO standards instead. This revolutionary, hand-held P2 camcorder provides 1080i and 720p recording with the production proven image quality of 100 Mbps DVCPRO HD. The AG-HVX200 records on a P2 card in 1080 in 60i, 30p and 24p; in720 in 60p, 30p and 24p; in 480 in 60i, 30p, and 24p either in DVCPRO50 and DVCPRO. On the newly-announced 8G P2 card, the AG-HVX200 records for 32 minutes in DVCPRO or DV, 20 minutes in 720p/24, 16 minutes in DVCPRO50, and eight minutes in 1080i/60 and 720p/60. $6,000 without memory cards.
- JVC GY-HD100U has many of the features professional videographers have been waiting for in order to migrate to HDV. The GY-HD100U utilizes three newly developed 1/3-inch CCD image sensors, each one featuring an array of 1280x720 pixels. The camera includes a standard detachable 16x Servo Fujinon HD lens. Other available lens options include a 13x (3.5mm) wide zoom HD lens, a wide-angle converter for the standard 16x lens, and an adapter allowing standard ½-inch lenses to be used on the camera. You also get 2 XLR audio inputs with independent controls for each channel. The GY-HD100U's unique compact shoulder design locates camera and viewfinder controls on the left side of the unit. The specially designed Fujinon HD lens provides automatic or manual iris control, with smooth servo zoom and backfocus adjustment. A convenient IEEE1394 interface permits simple, quick connection to an external dual media recording option, a PC or NLE for easy downloading, and editing or archiving. Under $6,000.
- Sony HVR-Z1U. 1/3-Inch 3-CCD HDV Professional Widescreen Mini Camcorder, Records and Plays HDV, DVCAM and DV Formats, HD and SD Down Convert, NTSC/PAL. Blurring the line between consumer and professional video cameras Sony has created the HVR-Z1U camcorder. It adheres to the HDV Consortium's specifications for 1080i recording on popular DV mini cassettes. The HDV video standard will provide about double the resolution of the old standard DV formats. It records and plays in DVCAM, consumer DV (SP mode), and the HDV formats. You may use the LCD screen simultaneously with the viewfinder. The design of the camera is aimed directly at the filmmaker, the most modern event video producers and even widescreen news shooters. Because it records in high definition and standard definition modes it can be used in a variety of production scenarios that may change from client to client or evolve over time. It is NTSC and PAL system compatible as well. $5,000.
- Sony HVR-A1U. Uses a single 1/3-Inch imaging chip. Professional HDV Camcorder with 3-Million Pixel CMOS Imager, DVCAM and Mini DV Recording Options, Professional Audio Inputs and Time Code. The Sony HVR-A1U is the entry level HDV camcorder that records high definition video as well as DVCAM and DV standard-definition video. The camera uses a single three million pixel CMOS chip to capture images. The use of a CMOS (Complementary Metal Oxide Semiconductor) chip allows the camera to capture amazing high quality images while consuming less battery power and making the camera smaller overall. The Enhanced Imaging Processor (EIP), a Sony created technology, enables the camcorder to capture and process high-definition video and high resolution still images with the highest levels of contrast and detail. $2,700.
For high-end digital filmmaking the choices are:
- Sony HDW-F900/3 Cine Alta. The HDW-F900 CineAlta camcorder is capable of capturing images at 24/25/30 frame progressive or 50/60 interlace at 1080 resolution. The HDW-F900h utilizes a 2.2 Mega Pixel FIT CCD and comes equipped with various gamma curves for superior imaging. The camcorder features dual filter wheels, comprehensive software adjustment parameters for superior image control. Memory Stick setup system saves and recalls various parameter settings. $91,100.
- Panasonic HDC27F Varicam. The AJ-HDC27 VariCam HD Cinema Camera brings variable frame rate acquisition to the DVCPRO HD product line up. This is the first high definition production camera that is capable of variable frame rate at the touch of a button. Individual frame rates may be selected from: 4-fps to 60-fps in single frame increments. Frame rates may be changed during recording. Designed as a high quality production camera, this native 720p camcorder can be used for 60-fps or the film-like 24-fps acquisition. When acquiring for 24-fps projects, higher than 24-fps operation can be processed for slow motion effects while slower than 24-fps operation can be processed to speed up motion. Additionally, the variable frame rates and related variable shutter speeds create some very interesting ghost like motion blur effects, warp speed zoom effects, and long exposure still shots typical of what one might see in music videos, sci-fi dramas and dream sequences. $65,900.
Which HD camera is best? Which HDV camera is best?
A recent article in DV Magazine compared four of the recent "pro" HDV cameras against each other and against the Panasonic HDC27F Varicam and the Sony HDW-F900/3 CineAlta. Surprisingly when tested for resolution, image quality and light sensitivity, the six cameras were more alike than they were different.
The two much more expensive cameras had better images than the much less expensive HDV units but the difference was much less than the hype would suggest. The four HDV cameras were also much more alike, in terms of picture quality, than they were different.
There are obvious differences in these cameras in terms of features, lens quality, ruggedness and suitability to purpose but the testers concluded: "We came away convinced that any of the cameras would do a creditable job in the hands of a skilled user, and that the choice of camera should be made more on features and ergonomics than on image quality."
Mini-DV equipment is available for filmmakers on an even lower budget. You may be able to get a deal purchasing or renting. Top models are:
- Panasonic AG-DVX100
- Sony DSR-PD150
For 16mm filmmaking some top choices include:
- Aaton A_Minima a small, light-weight super-16 camera just write for independent film production.
- Arriflex 16 SR3 has been around for more than 20 years but with the latest lenses this is a quality work-horse piece of equipment.
- Idonoskop A-Cam is an extremely tiny hand-held camera holding enough film for 2 minutes of shooting.
And for 35mm:
- Aaton 35-III
- Arri 235
- Panavision Millennium
Camera tripods and other camera supports
High quality tripods and tripod heads are available from:
For filmmaking it is important to use a very stable tripod and fluid head. Fluid heads use a sealed chamber containing oil or other dampening material to give the head a very smooth movement.
Your audio workhorse will be your shotgun microphone, boom and mixer. In this illustration the boom operator stands out of the way to the right while he suspends the microphone over the actors trying to get as close as possible without the boom casting a shadow or getting into the camera's field of view.
For outdoor filming a "long shotgun" is preferred. It gives the most directional pickup of sound to get the clearest reproduction of the actor's dialog while reducing the amount of ambience noise picked up.
Long shotguns tend to pick up too much echo when used indoors so a short shotgun or cartioid microphone is generally preferred.
Top long shotguns good for picking up clear dialog at a distance of 4-5 feet include:
- Sennheiser MKH816
- A/T AT4071a ($1000 list)
- A/T AT815a is less expensive
Top short shotguns good for picking up clear dialog at a distance of 2-3 feet include:
- Sennheiser 416 ($1040)
- A/T AT4073a ($850 list)
- Sennheiser K3U/ME80 ($500)
- A/T AT835B ($240)
The boom pole consists of the boom itself, generally made of fiberglass, a shock mount to isolate the microphone from handling vibration, a wind blimp cover and cable.
A lavalier microphone might be used if it isn't practical to use a boom, for example in a long shot where the boom can't get close to the actors without being in the shot. Lavaliers are tiny microphone that can be hidden in the actors clothing or taped to the side of their face away from the camera.
Most lavaliers have an omni-directional pickup so must be placed very close to the actor's mouth to get clean sound. They are also very sensitive to picking up wind and clothing noise.
Some industry standard lavalier mikes include:
- Sony ECM-55
- Sony ECM-30 is newer, cheaper and also very popular
- ECM-44B ($255list) is a good compromise of sounding good with voice but less bothered by wind and can be farther from the sound source.
For mixing with popular boom mikes:
- Sennheiser MKE-2 ($240)
- A/T MT830
- Sony ECM-77B
Other highly recommended lavaliers include:
- Sony ECM-77B ($465 list)
- AT MT830R ($155)
- Sennheiser K2 lav
- Shure WL50 lav
Radio, or wireless, transmitter/receivers are used, usually in combinations with lavaliers, when it is not possible to run a wire from the actors to the sound recording device. This can happen when the actors are walking and talking at the same time and a boom can't be used.
Radio transmitters are very sensitive to electrical interference and dropouts and are the last choice for picking up sound.
Lectrosonic wireless systems are generally considered to be among the best but most of the top microphone manufacturers make high quality wireless transmitters/receivers. Often a matching lavalier microphone is bundled with the wireless transmitter to make a complete solution.
Audio mixers balance and control the signal strength of the microphones as the sound is passed on to the recording device. Some recording devices have some ability to control the sound volume built in but it is always better to have a separate mixer that a dedicated sound technician can use.
Good mixers include:
- Samson Mixpad 4, about $200, battery operated
- Mackie 1202VLZ PRO 12 Channel Mixer with 4 Mic Inputs, about $300, requires A/C
- Shure FP-33 Stereo Mixer, about $1,300, battery operated
Companies manufacturing lighting equipment of interest to filmmakers include:
Also see the Production page on Lighting for the various techniques involved in film lighting.
Movie expendables and general supplies you might want to have on set
Use this list as a starting point for your list of expendables to have available at all times.
- Absorbents, paper towels
- Adhesive sprays
- Barricade ribbon "caution"
- Contact cleaner
- Dust masks
- First Aid
- Fluorescent light bulbs
- French chalk (talcum powder)
- Grip bags
- Hand tools, hammer, screwdrivers, etc.
- Heaters, electrical or gas/propane
- Janitorial supplies, broom, dustpan, rags
- Liquid wrench
- Oil absorbent
- Paper, brown kraft #40 roll
- Plaster, casting 20 minute
- Plaster, dental 6 minute
- Rain gear, ponchos and tarps to cover equipment
- Razor blades
- Snow, plastic artificial
- Stretch wrap 18"
- Tape, gaffers, masking, packing
- Tongue depressors