Create the Video

Digital video requires several components to successfully provide a video file to a viewer. First, unless the video exists as a native digital video file, as created by a digital video camera, it must be encoded, or represented in digital bits, that can be read and operated upon by a computer processor. An important concept in video encoding is the pixel, or picture element, which is a two-dimensional base unit of programmable color, also represented in bits. A pixel is a logical rather than an absolute unit of measure, since its physical representation can vary based on a number of factors, such as the bit depth and screen resolution of the computer used to display the pixel. The color represented in a pixel is a blend of some component of the red, green or blue color spectra, since the human eye perceives colors in these spectra.

Colors in digital video are represented, like all digital information, in bits. The more bits employed to produce the color (8-bit, 16-bit, 24 bit, etc.), the more precise the representation of the blend or hue from the red, green, blue (RGB) color space of the original. Digital video works identically to analog film and video in that the technology involves the rapid viewing of consecutive, still images to create the illusion of forward motion and actions evolving over time. Just as in analog film and video, one or more synchronized audio and text tracks can be added to the video tracks to create a composite audiovisual file.

Working with analog video

If you are using an analog camera, such as a Hi-8 video recorder, you will have to convert the analog video into digital bits, using a video encoding card, which is inserted into an open slot on your computer chassis.

A video encoding card accepts inputs from an analog source, such as a VCR or video camera, and converts the analog signal to bits. A video encoding card also includes audio encoding and must be cabled for both audio and video inputs. Encoding software and hardware are available in a range of costs and offer a range of capabilities, including different levels of compression, integration with video and audio editing software, such as Adobe Premiere, support for multiple frame sizes, and support for multiple encoding formats, such as M-JPEG, QuickTime, MPEG-1, MPEG-2, MPEG-4, RealVideo, etc. An encoding card that creates M-JPEG files will give you the most flexible options for further editing.

Creating a native digital video

Step One: Select Equipment

There is a wide variety of equipment available for creating effective digital videos. This website does not recommend specific equipment, but instead describes some of the component pieces—hardware and software—that can be used to create digital video. Any hardware or software mentioned is for illustration only and does not constitute a recommendation. The component pieces are:

Digital video camera

A well-reviewed consumer-grade or “prosumer”-grade digital video camera (“camcorder”) can be used to create effective digital videos that are easy to distribute to students and fellow educators. There are many sources of reviews for digital video cameras on the Web. Features to look for include:

File format created. You can purchase digital video cameras that produce video in MPEG encoding formats that are optimized for CD-R (MPEG-1) and DVD-R (MPEG-2). MPEG-1 and MPEG-2 videos are very high quality but compressed in such a way that does not allow further editing. There are editable versions of MPEG-1 and MPEG-2, but these versions usually require special software. A camera that writes to the mini-DV tape format, or creates M-JPEG or native AVI or Quicktime video provides you with better options for editing. As you will see below, the ability to edit is important.

Export options for the video. Digital video should be readily exported to a computer for further editing and uploading to the Web. Digital video cameras may have a FireWire, USB or SCSI port. Be sure to select a camera that has export options to several versions of Windows (e.g., 98, 2000, XP and NT), and MacOS to provide maximum flexibility for exporting files to a computer. The ability to play the video directly on a television is also useful for viewing videos in the classroom. All necessary cables for transferring the video to the computer or viewing on a television screen should be provided or readily purchased as accessories.

Zoom. Digital video cameras will provide both optical and digital zoom capabilities. Optical zoom provides you with true zooming capability and should be at least 10X or higher. Digital zoom simply enhances the optical zoom image, to create the appearance (but not the reality) of further enlargement. The more that you zoom with the digital zoom capability, the greater the artifacts, such as distortion and pixelation, will be.

Focus. Prefer a camera with both autofocus and manual focus, which will allow you to selectively focus on a foreground image, while allowing the background to blur. This has the effect of emphasizing the main image and eliminating the distractions of a busy background scene.

Auto Exposure Pre-sets. The camera should provide a number of pre-sets for different lighting conditions, such as daylight, low light, high speed action, indoors, twilight, snow and sand, etc. These programmed exposure pre-sets can take the guesswork out of different video scenarios.

Low light capabilities. An infrared or long-shutter mode will let you capture images in dark settings. If you plan to create digital videos in natural settings, this is a useful option.

Front-mounted microphone. A front-mounted microphone provides the least interference for sound capture since the line from camera to sound is direct. An external mic is always preferred, so be sure that a connection for an external mic is provided.

Separate sound channels. A really good prosumer camera will provide a separate line in for recording sound on a separate channel for mixing later.

Charged Coupled Device. The charged coupled device technology within the camera samples the image digitally for color and shape. The larger the image created, the greater the sampling. A high-end “prosumer” camera will provide three separate CCDs to capture each of the three RGB color spectra (red, green, blue), for the most faithful fidelity to the image color.

Battery and file storage. If you are recording a lengthy event or recording from the field, a long battery life and flexible file storage options are important. Removable storage will provide the best flexibility for lengthy taping sessions.

Size, appearance. The size and weight of the digital camera can be important if you will be carrying the camera for any distance. A good viewing screen is very important for setting up the video, establishing lighting and background, as well as previewing the file to insure that you have captured an acceptable video. Test the view screen in a number of settings, including indoors, low light and bright sunlight, before purchasing the camera.

Tripod

A tripod, with full pan and tilt adjustments, is required. It is impossible to hold a digital camera without creating some jitter, which really compromises the usability of the video.

Digital audio recorder

A digital audio recorder that creates audio in an editable format, such as WAV or AIFF, is recommended. In many cases, it is better to create the video without sound and to add an audio track later. A separate audio recorder can provide a number of options. If you expect to only capture speech, a good quality digital recorder for dictation or speech transcription is acceptable and may provide the added benefit of speech to text translation, using integrated speech recognition software. As with the digital video camera, select a digital audio recorder that can connect to your computer and upload audio files without requiring further encoding. The audio recorder should connect with a standard USB or FireWire connection. The digital audio recorder should be able to accept an external mic for audio input and headphones for playback. A digital recorder that is speech or sound activated can conserve recording space and may make editing easier, but may make it difficult to sync audio to video, so be sure that the sound activation mode can be overridden. Select a digital audio recorder that creates at least 22050 Hz (22 KHz), with 44100 Hz (44.1 KHz) preferred. 22 KHz creates CD quality sound, while 44.1 KHz creates DVD quality. For speech, 11025 Hz (11 KHz) is acceptable, but if music, sound effects or background noise will ever be captured, prefer a recorder capable of 22 KHz or higher. If you can afford it, a stereo recorder capturing 44.1 KHz is preferred. Multi track recorders for the prosumer music recording market may be available used or reconditioned at an acceptable price, but add a level of complexity that is not needed for creating science digital videos. A multi track recorder together with a mixer for combining multiple audio tracks may be available in your school’s music or media arts department. If you want to layer a music sound track to narration, a multi track recorder might be useful, but is overkill for most educational applications.

Microphone

A good microphone is essential for quality sound, whether you are capturing the sound simultaneously with the video through the digital video camera or adding a sound track later, using a digital audio recorder. There are two basic types of mics. Dynamic mics do not require an external electrical source, but instead have a small amount of on-board power. Sound is generated when the sound waves hit the diaphragm. Condenser mics are powered by electricity and are more sensitive to nuances of sound. Mics are also characterized by direction—unidirectional mics pick up sound in one direction only, which can minimize noise but also can create a sound that is artificial and flat since no background ambience is captured. For example, a narrated walk through the woods can sound very artificial if rustling leaves, bird sounds, etc. are not also captured. An omnidirectional mic captures sound in every direction without distinction. That same walk in the woods can be very confusing with an omnidirectional microphone, since the leaves rustling underfoot are captured equally and may drown out the narration. A cardioid microphone picks up a range of sound in a heart shaped direction, similar to a unidirectional except that the range of the mic extends in a heart or fan shape. The mic connection is also important. Most digital video cameras and recorders will accept a standard 1/8” or ¼” connector. A high quality mic will probably utilize an XLR connector. If you purchase a high end mic, be sure you are able to find an adapter and an impedance matching transformer. The adapter without the impedance matching transformer will not be adequate since the impedance of the microphone will be different from that of the recording device. It is probably best to purchase the best mic available that can connect directly to your audio recorder and video camera. If possible, choose a mic that is grounded to avoid picking up competing frequencies, such as radios.

Lighting

Lighting is discussed in step three, below.

Step Two: Establish the setting.

Setting is critical for good quality video. If you plan to share your video over the Web, you may need to further compress the video and reduce the dimensions of the video frame. Further compression can cause distortions to color, such as fuzziness or pixelation. You should to start with the sharpest colors and optimum contrast, to provide the most leeway when the video is reduced for sharing over the Web. Choosing the appropriate setting can be critical to create a video that maintains good quality when compressed for the web.

Prefer a neutral background with controlled ambient lighting. If you are filming indoors, you want to be able to control the indoor and outdoor lighting. Freestanding lights can be preferable to overhead lighting. It is very difficult to control unwanted shadows and light bounce from overhead lights. Light from windows should be controllable with good shades or lined curtains. The best background is a neutral gray color. Avoid filming against a white wall, since any light will bounce against the wall and may cause excessive back lighting. If people are being filmed, they should dress in solid colors rather than a busy pattern that can cause a moiré effect.

If you will be capturing audio directly, choose a location without background noise, particularly the hum of equipment, such as elevators, electrical closets or plumbing. Also avoid being near high traffic areas with phones ringing, conversations, feet tramping, etc.

Step Three: Lighting

Digital video cameras come with pre-set exposures for many standard lighting conditions. However, if you want to create digital videos that are good quality, effective, and reusable in a range of frame and file sizes, lighting is perhaps the most critical component for creating sharp videos with well-defined shapes and colors. If you want to create many digital videos on an ongoing basis, you may want to invest in a basic lighting setup for digital video. If you want to create a single digital video of good quality to reuse for many years and to share with others, you may want to rent or borrow a camera lighting set up. Your school photographer, local camera shop or photography studio should be able to assist you in determining your needs and locating a source to rent or lend a lighting set up. If you want to purchase lighting, you should be aware of the standard elements of a lighting design for stationary filming, such as a lecture or an experiment.

The cheapest alternative is to work with actual lights available in the room, such as ordinary floor lamps. If you purchase standard floor lamps for use, prefer lamps with adjustable cone shades that can be “aimed”. Paint the metallic cone shades a standard gray or black instead of any colors provided. You will want to use bulbs of at least 100 watts, or higher. You will also want to use reflectors to diffuse the light, to prevent the light from washing out the image, creating bright spots or harsh shadows and to direct diffused light where it is needed for illumination. You can create reflectors, to bounce and diffuse the light, by using white poster board or poster board covered in aluminum. Create both shiny and matt reflectors by using both sides of the aluminum foil. You can also use an aluminum dashboard protector or aluminum face tanner.

If you can afford them—for purchase, borrowing or rent, a good lighting kit providing free-standing front, back, and fill lights, as well as reflectors, is a good purchase, particularly if you intend to continue creating digital videos. A camera store can assist you with standard lighting. According to Steve Smith, a standard versatile setup is two 300w and one 50w fresnel lights [3] Consider adding a collapsible silver umbrella reflector and a set of gel sheets. Gel sheets can compensate for different light color, which varies depending on weather, time of day or type of light bulb in existing light. Direct sunlight has blue tones and indoor lighting can have orange tones. Experiment with red, blue or green gels to compensate for color changes provided by any unavoidable illumination.

Key light. This is the main light, which faces the subject, usually angled from the front. This is generally a focusable light source, such as a 300w fresnel light with barn doors to adjust the quality and quantity of light provided. The key light will be angled—about 45 degrees off axis for the subject’s face or other focal point.

Back light. A back light may be set behind and above the head or shoulders of the subject. It can also illuminate the background by throwing light to a white wall or reflector behind the subject or throw light directly at the subject from behind.

Fill A fill light insure that shadows are not too harsh by providing additional illumination wherever it is needed. Fill lights are often diffused to prevent so much light that the image is washed out. Fill lights can be diffused by bouncing the light off a reflector, such as a silver umbrella. A cheap alternative to the professional silver umbrella is to bounce off a white card, such as white poster board or a sliver dashboard protector for a car. A fill light may illuminate the subject directly but be diffused through the use of a gel.

Fill and backlights may be aimed at any reflector source, such as a ceiling or white wall. The goal is to provide enough shadow to add depth and dimension so that the subject is not flat but not to cast harsh shadows or wash out detail.

Examples of lighting effects:

Derived from Smith, Steve. "Video Lighting Part II" in The Digital Journalist, issue 12. http://www.digitaljournalist.org/issue0012/videosmith.htm

Derived from: Film & Video Lighting for Low-Budgets. http://www.exposure.co.uk/eejit/light

Step Four: Audio

For narrated events, where the video and audio do not need to be synchronized, you will prefer to create the audio track separately from the video. This is done for two reasons. To begin with, the actor can concentrate on performing the action, such as a chemistry experiment or mathematical problem. It is easier to perform tasks smoothly when you are not distracted by reading a script. It is hard to stay on track if you speak extemporaneously and perform sequential actions. Also, the clinking of glass and metal can compete with the narration. It is better to sacrifice some verisimilitude by eliminating the sounds of an experiment or activity or by adding a narration as a separate sound track that can be artificially enhanced to be heard over the activity sounds. In the case of a lecture or an interview, where the audio must be exactly synchronized to the video, it is best to conduct the interview in a sound proofed room or by selecting a room away from any mechanical or outside noises. Your options for editing sound quality for synchronized audio and video are very limited and consist usually of normalizing the sound so that all of the audio track is in the same dynamic range or volume level or amplifying the sound. Any editing, such as eliminating hiss or silences will generally cause the audio to lose synchronization with the video. For synchronized audio and video, it is best to use whatever adjustments are provided by video editing software. It is very difficult—perhaps impossible—to edit an audio track separately without losing synchronization with the video.

If an audio track is created separately, for voiceover narration, it can be edited to remove silence (when necessary), remove hiss, hum, and pops, normalize for uniform dynamic range and volume, equalize to amplify certain frequency ranges, smooth the audio to emphasize low frequency sounds, emphasize, to highlight the high frequency sounds, and apply a noise gate to remove excessive hissing or background noise.

Step Five: Filming

These recommendations focus on the scenario of documenting an experiment or activity illustrating a scientific concept or procedure. There are many web sites that provide advice on nature photography and videography. Filming multiple speakers, such as a two-person interview, usually requires two cameras with separate mics for each speaker. This website focuses on the single subject performing an experiment or activity, as a common science video scenario. Much of the advice can be applied to other science subjects, however.

Bear in mind that the video you create may ultimately be edited for a range of bandwidths available over the Internet—56 KB modem, DSL or Cable modem, and T1/LAN or higher. Video to be shared over the web will be compressed for streaming at lower bandwidths. In order to retain picture quality at low bandwidths, the frame dimensions will also be reduced. It is important to keep camera movement to a minimum, and to keep subject movements crisp and economical.

Your digital video camera will automatically balance white and black points for the available lighting. However, some video cameras will allow you to balance the camera manually against white and black color cards. You may also be able to insert RGB color bars at the beginning of the video, to support color correction later.

Always begin filming a few seconds before the experiment or activity starts, as well as a few seconds at the end. Otherwise you may lose a few seconds at the beginning or end, either because the camera is self adjusting for lighting level, resulting in a capture delay, or a few seconds may be lost when transferring the video into your computer.

Changing the visual elements between shots adds interest to the video. For an experiment, a standard storyboard might include the following:

Framing shot: Shows the person conducting the experiment, and the entire experiment area.

The experiment—one or more shots demonstrating each part of the experiment. Separate shots may occur if the experimenter moves from behind the desk to retrieve ingredients, thus altering the shot composition. For an explanation between experiment tasks, a shot may focus on a head or head through waist shot of the experimenter. As long as movements are smooth and economical, and ingredients are ready to hand, a single shot may document all the stages of the experiment. However, you may prefer to document each step in a single shot and freeze frame the end of each step, to emphasize the step. Experiment with the right length for creating a freeze frame with a still frame, to avoid poor pacing. After filming the experiment or activity, you may choose to end with a framing shot of the experimenter and the experiment area, or end with a text frame that might include a bulleted list of the experiment steps

Use a tripod for stabilizing the camera and controlling camera and lens movements to avoid the jerkiness inherent in handheld filming. A tripod should allow some movement to angle, pan and zoom the camera to move between the framing shot and a closeup of hands conducting the experiment. Sometimes it may be appropriate to film each shot separately rather than in a single filming, particularly if multiple takes are needed for each step in an experiment. If a video is separated into separately filmed segments or shots, you will want to plan for creating transitions between scenes or shots. Transitions may consist of a transition element, such as a cross-dissolve—between each shot. Transition elements are provided in video editing software, such as Adobe Premiere or Apple’s Final Cut Pro. Experiment with transitions on low bandwidth video files, at 7.5 frames per second. Most transitions perform very badly on low bandwidth files, although I have had good success with cross dissolve transitions on low-bandwidth video files, as created in Adobe Premiere. Fade to black can also be created by creating black frames that overlap and connect consecutive shots. Video editing software provides the ability to create black frames for creating black fades.

Step 6: Editing

Digital video should be imported into your computer for further editing. A computer should have significant RAM, or working memory (256 K to 1 Gb RAM) and sufficient contiguous storage. Before beginning to work with digital video, it is a good idea to defragment the hard drive to insure sufficient contiguous space (1 Gb or more) for each video file that you create. Generally, you should close every other application, including virus checking software, when importing and editing video files.

Editing software such as Premiere or Final Cut Pro will create a work area that shows a linear file broken into logical or actual frames. Frames are essentially still images that can be cut, pasted and copied. Applying a transition applies transition frames on a separate track. Black frames can also be applied. Each shot would be placed on a separate track to create the overlap needed for transition or fade to black between segments.

One editing task will be to cut the few seconds of necessary “dead air” that you created at the beginning and end of your filming.

You can also do some correction for hue, contrast and brightness to compensate for problems with lighting that were not corrected during filming.

Editing software can also transcode video files into multiple formats for sharing over the web. Media Cleaner Pro is an example of software that can transcode into multiple formats to provide end users with options for viewing the video over the web.

Transcoding videos for the Web are discussed in the next section, “Share the video.”