Video

Question 1

Advantages of video

Answer 1

Advantages
Shows real-time images
Monitoring diver safety
May be streamed via the internet to a remote location
Instant playback
Generates a permanent record
The video may be overlaid with telemetry Efficiency may be improved by topside specialists
Can be accompanied by a commentary Remote-control cameras deployed in hazardous areas
HD video is available, records excellent quality images

Question 2

Disadvantages

Answer 2

Disadvantages
Commonly, only a 2-D image is recorded (3-D camera systems are likely to be more widely used)
Image quality is not as high as a digital stills camera (Modern systems may produce acceptable images)
Analogue recording/copying degrades image quality (Digital recording systems record/copy in high fidelity)

Question 3

What are the basic components

Answer 3

 Underwater light - separate or combined with the camera.
 Light & video cables contained in the diver’s umbilical.
 Power supply/video controller - supplies the camera with a constant voltage supply & a variable supply for the light.
 Decoder/recorder will be part of the monitor, or a computer.
 Video typewriter & overlay writer.
 Picture-grabber & printer.

Question 4

Types of cameras

1 CCD explain

Answer 4

There are three types of camera commonly used underwater. Charged Coupled Device (CCD) Camera. CCD refers to the type of sensor used to capture the image.
 It is the same type used in digital stills cameras
 The most widely used type of video camera CCD cameras have the following features.
 Colour.
 Good resolution.
 Compact & lightweight.
 Solid state - no moving parts & are robust.
 Not damaged by bright lights or magnetic fields.
 Excellent depth of field.

Question 5

Silicon Intensified Target (SIT) Camera.

Answer 5

Silicon Intensified Target (SIT) Camera.
 Is an image intensifier – i.e. a low-light camera.
 Used for ROV navigation & long range viewing.
 Useful in turbid water, when the intensity of the video lights may be turned down to reduce backscatter.
SIT Cameras have the following features:  Monochrome.
 Lower resolution than CCD cameras.
 May be damaged by bright light.
 Generally larger & more bulky than CCD cameras.
 Often deployed by ROV.

Question 6

Near-SIT CCD Cameras.

Answer 6

Near-SIT CCD Cameras.
 Although these CCD cameras do not have quite such good low-light performance as a SIT camera, they do have very good low-light characteristics.
Have the following advantages over SIT cameras:
 Higher resolution.
 Lighter & more compact.
 More robust.

Question 7

Encoding

Answer 7

Images are encoded by the camera to form the video signal.
 The image is broken down into a number of lines, each containing a number of pixels.
 The number of lines is a good indicator of the picture quality – more lines, higher the quality.
There are two basic types of video encoding:
 Analogue.
 Digital.

Question 8

Advantages of a hat mounted camera

Answer 8

Advantages
Constantly active, for monitoring safety & efficiency
Shows the diver’s point-of-view
Diver can respond to topside camera commands
Diver has both hands free
Light & camera fixed to the helmet, so always aligned Diver or 3.4u can give a commentary
Diver has eyes on, can give a description of features & respond to questions

Question 9

Disadvantages of a hat mounted camera

Answer 9

Disadvantages
 Helmet may not be manipulated into small spaces.
 Parallax error must be managed by the diver.
The closer to the subject, the greater the parallax error

Question 10

Advantages of a Hand held camera

Answer 10

Advantages
May be manipulated into small spaces Diver or 3.4u can give a commentary
Diver has eyes on, so can give a description of features & respond to questions

Question 11

Disadvantages of a hand camera

Answer 11

Disadvantages
Not constantly active - on only during inspection
Parallax error Light & camera not on same platform, not aligned
Diver has only one hand free

Question 12

ROV mounted camera

Answer 12

Advantages
Vehicle not limited by fatigue or decompression
Safely deployed in hazardous environments
Powerful lights giving excellent illumination
Multiple cameras –best chosen for any condition
Multiple sensors may provide detailed telemetry

Question 13

Disadvantages of ROV camera

Answer 13

Disadvantages
Access may be restricted, e.g. by structure geometry or debris
Poor stability when operating in shallow water in rough conditions
ROVs are less versatile than divers
No human eyes on the subject view is limited by the quality of the video system

Question 14

Remote fixed camera advantages

Answer 14

Advantages
Constantly active
Safely deployed in hazardous environments
May have remote pan, tilt & zoom controls Excellent stability Ideal for continuous monitoring

Question 15

Disadvantages of remote camera

Answer 15

Disadvantages
Limited to one specific task
Requires regular cleaning
No human eyes on the subject view is limited by the quality of the video system

Question 16

Preparation of camera

Answer 16

Preparations for the dive will include:
 Inspect for damage.
 Lubricate any seals.
 Test any RCD’s or other safety features.  Function test the video system.
 Centre camera & light on their brackets.
 Prepare the video log sheets & recorder

Question 17

Post inspection

Answer 17

Post Inspection Actions:
 Rinse the camera in fresh water. 
 Clean the lens & fit the lens cap. 
 Inspect for damage. 
 Store in a dry, well ventilated place. 
 Complete the video log. 
 Finalise the DVD & label the disc. 
 Back up data on hard drive.