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T351 Week 2

Agenda:

  • Cameras & lenses (Cont.)
  • Readings:
    • Week 1: cybercollege.com 10, 11, 12, 17, 19, & 20. (cameras & lenses)
    • Week 2: cybercollege.com 50, 51, 52, & 53

Misc. Announcements

  • No lecture this week (due to MLK Day)
  • Interview/Feature Story pre-production work (program proposal) is due by the start of lecture next week. Turn it in to the Oncourse/Resources/Interview Exercise folder. We'll share these in lab. You'll need to contact and schedule with your subject soon.
  • Think about your other projects as well. Please consider taking on a project for a real-world client. Planning and scripting these ahead of time is critical. Remember that the success of a video is determined in preproduction. If you think through, plan and coordinate your project, the production will be easy.

Camera / lens review:

  • CCD - Stands for Charge Coupled Device.
  • CMOS (Complementary Metal-Oxide Semiconductor)
    • CCD and CMOS sensors convert light to electrical energy. Lens diameters match CCDs, so a 2/3" lens would be mounted on a camera with 2/3" CCDs. The bigger the CCD, the more pixels you can fit on it. (The Sony Z1Us use three 1/3" CCDs, the Z7Us have 3 1/3" CMOS imagers, the Thompson cameras in Studio 5 use 2/3" CCDs)
  • Resolution (Horizontal resolution is determined by the maximum number of vertical lines resolved. Requires a test chart.) The studio camera heads can resolve about 700 lines. VHS tape can only resolve about 230 lines.
  • Gain (boosts signal and adds noise)
  • Focal length: (Don't confuse with depth of field!) the distance from the optical center of the lens to the focal plane (CCD or target) of the camera). When focused at infinity, a 10 mm lens will be 10 mm from the film plate or CCD.
  • Zoom lens - The focal length can be continuously varied
  • Angle of view (Telephoto lenses have narrow angles of view, while wide angle lenses have wide, or large angles of view.
  • Zoom ratio: Often (but not always) given in a ratio or two numbers (e.g. 12 x 10) The first number represents the minimum focal length in millimeters, and the second number the multiplier. A 12 X 10 zoom lens would have a minimum focal length of 12mm and a maximum focal length of 120mm.
  • Compressing distance: telephoto lenses provide the effect of compressing distance
  • Changes in apparent speed: Telephoto lenses also have the effect of slowing down Z motion. (The Z vector is directly in-line with the lens- as opposed to up and down or let to right.)
  • Perspective changes - Wide angle lenses can cause distortion
  • What is "normal”? A normal lens captures a field of view without visible distortion and that looks natural. To calculate the normal lens, measure diagonally from corner to corner. (e.g. a 50 mm lens would be "normal" for a 35 mm camera.
  • Lens speed - Lenses which let lots of light in (have large apertures or are capable of small f-stops) can be labeled as "fast". These usually cost quite a bit more than their "slower" counterparts.
  • F-stop - These numbers are inversely related to size of the aperture or iris opening.
  • Depth of field - the range of distance that objects will be in focus
  • Relationship between depth of field and f-stop - the higher the f-stop (smaller aperture) the greater the depth of field you will have.
  • Relationship between lenses and depth of field - wide lenses will have a greater depth of field than telephoto lenses.
  • Selective focus (related to rack focus and follow focus)
  • Follow focus
  • Rack focus
  • Macro focus
  • Auto focus (problems with)
  • ND filters - Neutral density filters don't influence the color temperature. They are gray and translucent. There purpose is to minimize the light coming into the camera.

Sensors

The lens focuses the light onto an imaging or pickup device. In the old days cameras used tubes, these days CCDs (Charge Coupled Device) or CMOS (Complementary Metal-Oxide Semiconductor) sensors are used. CMOS sensors are beginning to become more widely used as they are a bit easier to manufacture and use less power than CCDs. The tiny camera in your laptop or cell phone most likely uses a CMOS imaging device.

Most professional video cameras use a beam splitter, which consists of prisms. Some refer to this as the prism block. The incoming light is split into its primary components, Red Green & Blue and recorded onto three separate CCD or CMOS imaging elements. These elements are about the size of a postage stamp and convert the light energy into an electric charge. While the industry norm has been to use three imaging elements, a growing number, such as the Red One, are using a large, single CMOS sensors.

Here's a nice picture of a prism block from Adam Wilt's amazing and informative website:

prism block

Sensitivity

How much light does the camera need to operate? This is called minimum illumination or sensitivity. It’s measured in foot-candles (American) or lux (European) usually along with the required f-stop and gain needed to capture an image. For example Panasonic's AJ-SDX900 reported minimum illumination is 0.01 lux (F 1.4, +48dB +20dB gain).

F-stop

An f-stop represents the size of the aperture in an inverse manner. A large f-stop corresponds to a small aperture, or opening in the iris. A small f-stop represents a large opening. You should know your standard f-stops: 1, 1.4, 2.0, 2.8, 4, 5.6, 8, 11, 16, 22, 32. Increasing one f-stop will cut the light in half. Decreasing the f-stop by one will double the light.

The relationship between F-stop and depth of field: The larger the f-stop (or smaller the opening) the greater your depth of field will be. The smaller the f-stop the smaller/shallower your depth of field will be.

Think about this. You are on location shooting a MCU of your talent for an interview. The background is in focus and detracting from the subject. What can you do to make the background less distracting?

Aspect Ratio

Aspect ratios should be provided width to height. The two common aspect ratios of TV are 4:3 and 16:9.

  • 4 x 3 (or 1.33:1)
  • 16 x 9 (or 1.78:1) This is closer to 35 mm movies.

DTV (Digital TV)

The broadcast of NTSC (analog video) ended in Feb 2009. Broadcasters are now transmitting digital video using the ATSC standards (Advanced Television Systems Committee). Digital TV supports older 4:3 content and new, HDTV programs recorded in 16 x 9. The new ATSC standards also support a number of new frame rates. In addition to 60i we have 24p and 60p. Some of the new digital formats (standard and HDTV) use progressive scanning instead of an interlaced frame.

Progressive Scanning: The electron beam scans each line sequentially. It does not use two interlaced fields.

Common Digital TV formats include:

480p uses only 480 lines scanned at 60 frames per second (good but not HDTV)
720p uses 720 lines at 60 frames per second (HDTV)
1080i uses interlace scanning (each field has 539.5 lines) (HDTV)

ATSC HD delivery formats:

Horizontal lines

Vertical lines

Frame Rate

1280

720

60p, 30p, 24p

1920

1080

60i, 30p, 24p

Note that many HD production formats do not record the full pixel dimensions listed above. Some use few pixels horizontally, and then stretch the image upon output to the full pixel dimensions.

For instance 1080 HDV actually records at 1440 x 1080. Panasonic's DVCProHD 1080i uses 1280 x 1080.

Viewfinders

Why B & W viewfinder and not color?

The number of pixel elements in a CRT or LCD display determines the resolution. More pixels = greater resolution, right? Color monitors need phosphors for each of the Red, Green and Blue elements, where black and white monitors only need one. So given the same size CRT monitor or viewfinder, a black and white monitor will have 3 times more resolution than a color monitor. Since we are primarily concerned with framing and focus when we shoot, it's best to use the monitor or viewfinder with the sharpest display, which in most cases will be B & W.

Setting proper aperture

Monitors are nice but never trust them until you see color bars through it first. The same applies for viewfinders. Always check out the appearance of color bars through your viewfinder before manually adjusting the iris.

Waveform monitors and vectorscopes are used in both the studio and in the field.

  • Waveform monitors display brightness and timing information. The major setting to be aware of are:
    • ATSC (digital) black should be 0 IRE
    • NTSC (analog) black should be 7.5 IRE
    • The brightest portion of the screen should be no greater than 100 IRE
  • Vectorscopes show color information

While waveform monitors and vectorscopes are helpful, they aren't always available or practical in the field. This is one reason it's good to have the zebra stripe function on a camera.

Zebra Stripes

Zebra stripes are a visual aid that helps the camera operator set the proper exposure. (A switch on the Sony Z1Us and Z7Us will turn the zebra stripes on or off in the viewfinder.) Zebra stripes become visible when a certain IRE (brightness) level is reached. You can adjust the threshold brightness level through the camera menu. Don't use zebra stripes unless you know what they are set for.

Continuity Production & Editing

#1 rule: Don't confuse the viewer! This is why we strive to maintain continuity. Preserve the illusion of space & time. People and objects remain faithful to their positions (this can be tricky over days of shooting)

Edits must be motivated for the best continuity. When shooting think about how you will get from one shot to another. Will action motivate the edit? A sound?

Viewers create mental maps of where things are and expect time to progress forward.

An Establishing Shot or Master Shot, which is often a wide shot, establishes the initial relationship of people and things within a given scene or location. You can preserve this illusion by using the 180-degree rule when you shoot.

Review the 180-degree rule. (two people sitting at a table)

How to cross the line:

  • Subject changes attention or move gaze to establish a new vector.
  • Shoot down the line
  • Subject moves
  • Move the camera over line (dolly, crane etc)
  • Use a cutaway, then come back to your scene from a different vantage point

Viewers are getting more used to seeing the rule broken. (Which doesn't make it right.) Fox news (Bill O Reilly) is pretty good at breaking the 180 degree rule.

Insert shots – close up from a larger shot

Cutaways – cut away to something related (could be something happening simultaneously)

Technical Continuity

Unplanned changes in sound, lighting, video or setting is referred to as a technical continuity problem.

Moviemistakes.com has lots of fun examples of technical continuity problems.

A famous one is in T2, when the T2 liquid robot cop is chasing Ahnuld and little John Conner. The T2 is driving a semi, Ahnuld & John are on motorcycles down in a drainage canal. The T2 drives the semi off of the overpass down into the canal, and we can clearly see the windshield popping out. In the next shot of the front of the semi, the glass is back in the semi. That's an example of a technical continuity problem.

While your productions are not likely to suffer from an elaborate problem such as this, beware of common mistakes:

  • Changes in color temperature. Avoid mixed lighting locations and white balance whenever you change the locations.
  • Changes is light levels Keep lighting levels consistent within a scene.
  • Primary Audio - use the same mic, in the same manner when recording your talent. (Don't use a lav in one scene and a handheld on a stand in another)
  • Background audio - avoid abrupt changes within the same scene. Always record 60 seconds of ambient sound, which you can layer in to the audio mix.

Lab this week:

  • Cameras (Cont.)
  • Continuity techniques (Film style continuity vs. technical continuity)
  • Shoot storyboard / continuity sequence exercises. Don't forget to bring in 2 copies of your storyboards for next week's lab. Also bring your SDHC card to record your work.
  • Your Interview / Feature Story proposal is due in lab next week! Also think about your various projects. Planning and scripting these ahead of time is critical.
    • Art Video
    • Drama / Storytelling Project
    • Final Project

 

 


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