Chapter 8 Flashcards
(35 cards)
Three basic forms of communication
- Sight
- Sound
- Motion
Lens components
- The camera needs several lenses called elements to duplicate the complex working of the eye.
- A lens is two prisms joined together.
- If the prisms are joined at their apexes they from a concave lens that converges the light to a single point.
- If joined at the base, they form a convex lens that converges the light to a single point.
Focal Length
- Distance from the optical center of the primary lens to the point where the light converges on the focal plane.
- Focal length determines the field of view of the lens.
- Short focal length has wide field of view is called wide-angle lens.
- Long focal length has a narrow field of view and is called telephoto lens.
Different Types of Lenses
- Wide Angle: 4.5mm to 25mm (allows more control)
- Normal: 25mm to 75mm
- Telephoto: 75mm or longer
Zoom vs Prime Lens
- Advantage of zoom lens over prime lens (fixed lens) is that the focal length can be set at any point with the parameters for that lens.
- Prime lenses are generally of a higher quality than zoom lenses and are used on DSLRs and high-end cameras.
Focal Plane
• The point at which the light rays that pass through a lens converge and are in focus
Depth of Field
- The range of acceptable focus in front of and behind the plane of focus
- 3 factors affecting depth of field: Focal length, iris opening, distance from camera.
- As focal length increases, the dept of field decreases
- As the iris is opened up, the depth of field decreases.
- As the lens is focused on objects closer and closer to the camera, the depth of field also decreases.
MOD
• Minimum Object Distance- The limit of how close a lens can focus.
Aspect Ratio
• 4:3 (analog), 16:9 (like our normal human way of seeing things)
Iris
- Overlapping metal leaves or fins that rotate to make the hole smaller or larger. Controls the amount of light passed on to the focal plane.
- F-stops are used to measure the speed of a lens.
- Fast transmits a large amount of light.
- Slow transmits smaller amount of light.
Optical Groups of Zoom Lenses
- Focusing group- gathers light into a sharp, clear image.
- Variator group- Moves inside the lens to change the image size from wide angle to telephoto.
- Compensator group- Moves with the variator group to keep the image in focus & reduce aberrations caused by the first 2 groups.
- Prime lens group- Focuses the image on the recording surface, such as film or a TV camera chip.
Lens Extenders
• 2x range extender- doubles the focal length however it is limited in low-light situations.
Light Quality Control
- Ultraviolet filter- protects the lens from scratches, dirt, etc.
- Hood- Prevents direct light from striking the front element.
- Lens Flares- Circular patterns or reflections in the lens
Lens Filters
- Color enhancement- change the perceived color of light
- Diffusion- reduce the sharpness and/or contrast of the picture
- Special effects- Do everything from creating multiple images to split screen. Most of these things can be done in post production.
Proper Lens Care
- Loose dirt or dust can be blown or brushed away with a soft photo brush or an air blower.
- Do not use your shirt, tissue, or mouth.
Filter Wheel
- The 1st thing and image passes through in a network quality camera.
- Contains basic filters (clear, color correction, and light reduction)
CCDS and CMOS
- CCDS more expensive, less susceptible to noise in the picture, require more battery power
- CMO (Complementary metal oxide semi conductors)
NTSC
- National Television Systems Committee- reference system used in the U.S. from 1940s until 2009.
- Used 525 lines of resolution and scanned at 59.85 fields per sec.
ATSC
- Advanced Television Systems Committee
* 16 x 9, 1080 lines of resolution
Camera Functions
- Power Switch- Gives power
- Standby- Used when you don’t need to operate it, but want to start up quick.
- Save on- Gives you a pic in the viewfinder, but prevents the VCR’s tape servo motors from coming up to speed.
- On
- Camera bars- Makes the output of the camera either the picture or the color bar generator contained within the camera.
- Gain switch
- White balance, black balance
Monitoring Pictures
- Viewfinder shows exactly what the recorder sees
* Can show Zebra bars, which appear over parts of the picture to display the exposure level.
Shutter Speed
- Normal is 1/60 of a sec
- Fast shutter speeds allow for slow-motion pictures & freeze frames, but show a strobe effect when playback at the normal amount of frames per sec
Waveform Monitor
• Needed to make adjustments on the electronics of a camera.
Vector Scope
- Checks the color or chroma of the TV signal.
* Ex: If reds don’t look right this will tell whether it’s the operators eye, the TV set, or the camera that is wrong.