T351 Week 2/3
- Cameras & lenses (Cont.)
- Week 1: cybercollege.com 10, 11, 12, 17, 19, & 20. (cameras & lenses)
- Week 2: cybercollege.com
50, 51, 52, & 53
- No lecture 9/1 (due to Labor Day)
- Interview/Feature Story pre-production work (program proposal) is due by the start of lecture (9/9). 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
- 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
- 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
- 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
- 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.
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:
Image sensors come in many different sizes. The smallest, often found in inexpensive camcorders might have 1/4" sensors (measured diagonally). GoPros have sensor sizes of 1/2.5". The Sony NX5Us have 3 1/3" CMOS sensors. Our LDK4000 studio cameras in Studio 5 use 3 2/3" CCDs. Canon 60D and 7D DSLRs have APS-C sensor sizes, also known as cropped-frame. These are 22.3 x 14.9 mm, which is a little smaller than 35mm. Canon 5D, RED, Black Magic Cinema Cameras use full frame 35mm image sensors.
Here's an illustration showing many common sensor sizes.
The relationship between imager size and depth of field: The smaller the sensor, the greater the apparent depth of field will be. (Due to the physics of optics.)
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?
How to get video to look more like film
There are several reasons why films and videos have different "looks". The primary reason is related to the depth of field. Because video is captured on smaller sensors, it inherently has a wider depth of field. Video cameras also have servo zoom switches, which are absent on most film or digital cinema cameras. ANother reason is the frame rate.
In order to get the most cinematic look out of your video camera try the following:
- Shoot with the largest aperture possible (smallest f-stop). The will give you the shallowest depth of field.
- Exagerate the shallower depth of field with a telephoto lens
- Don't use the servo zoom lever
- Shoot in 24p
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).
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
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:
60p, 30p, 24p
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.
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
- 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 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
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
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)
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
- 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
- Background audio - avoid abrupt changes within the same scene. Always
record 60 seconds of ambient sound, which you can layer in to the audio
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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