Understanding Video Cameras: A Guide to their Components
The Video Camera
Optical Block
The optical system of a video camera is similar to that of any other camera. Key elements found in ENG (Electronic News Gathering) or EFP (Electronics Field Production) cameras include:
Diaphragm or Iris:
This has automatic and manual settings, often with remote control capabilities. Manual mode usually involves a key or button to switch between manual and automatic.Zoom:
Zoom can be automatic (with wide-angle ‘W’ and telephoto ‘T’ positions) or manual, controlled by a lever on the camera grip.Filters:
Two types exist: quality (color temperature) and quantity (neutral density). These are often combined in a single filter wheel. Color temperature filters are numbered, with higher numbers indicating higher color temperatures (e.g., No. 1 for 3,200 ºK, No. 2 for 5,600 ºK). Changing these filters usually requires a new white balance.
Electronic Block
This part transforms the optical image into an electrical signal, amplifies it, and processes it for transmission or recording. It consists of:
Electronic Capture and Sampling:
Older cameras used cathode ray tubes, but these have been replaced by CCD (charge-coupled device) and CMOS (complementary metal oxide semiconductor) sensors.Luminance and Chrominance:
The image signal is amplified and separated into luminance (Y) and chrominance (color difference signals U and V). This involves adjustments like pedestal and gain controls, gamma correction, detail enhancement, and PAL encoding.Timing and Control System:
This synchronizes the electronic block’s operation using a sync generator and timing generator.User Interface:
This facilitates communication between the camera and the operator. Important electronic controls include:Auto White Balance (AWB):
Adapts the camera to different light sources by referencing a white surface, ensuring all color channels produce the same signal level.Auto Black (AutoBlack):
Similar to white balance, but performed with the diaphragm closed, adjusting red and blue signals to match green and eliminate color dominance in dark areas.Gain:
Amplifies the video signal, measured in decibels. Each +3dB gain is equivalent to ½ f-stop. Higher gain increases sensitivity but also introduces noise.Shutter:
Electronic shutters control light exposure time, similar to mechanical shutters in film cameras. Different speeds are available (e.g., 1/60 to 1/2000 sec). Higher speeds reduce motion blur, flicker from fluorescent lights, and can compensate for higher f-stops.
Professional and industrial cameras offer additional controls for contrast, latitude, detail, and color response, accessible via buttons or menus. Some common ones are:
Contour Corrector (DTL):
Electronically sharpens the image by enhancing or smoothing edges.Dynamic Contrast Control (DCC):
Improves latitude in high-contrast scenes, reducing detail loss in bright areas.Master Black:
Adjusts the pedestal level, affecting the darkest parts of the scene and modifying contrast.