Features
Digital Video Camera Features
This page describes some of the features that digital video cameras can have.
Zoom
Zoom is the ability to magnify the image that you are shooting. There a 2 different ways zoom can be achieved. Firstly optical zoom, where an optical lens is employed to optically modify the light that falls onto the CCD. With optical zoom, the full amount of the CCD is used, meaning you still get as many pixels in the image as you do without zoom. The second zoom method is digital zoom. In this case, the centre of the image falling on the CCD is extracted and digitally modifyed to occupy the whole. This means that only the central pixels of the CCD are being used. The result is that the image does not have as much detail as it would if optical zoom was used instead. When very high digital zoom factors are used the picture becomes very low quality.
Camera manufacturers often provide high digital zoom factors, which result in very poor picture qualities. When comparing zoom figures, it is important to compare the optical zoom factor.
High Definition (HD)
Some cameras have “high definition” recording capabilities. This means that the recorded images contain more pixels (dots of colour) than standard definition.
Image Stabiliser
An image stabiliser attempts to compensate for camera shake. When taking shooting camcorder pictures, it is normal to be holding the camera in your hand. This results in inevitable wobble of the picture you are shooting.
When you enable the image stabiliser in the camera, it only uses part of the CCD for recording the image. The part of the CCD being used is dynamically changed using some movement detection algorithm. If you wobble slightly to the left and back again, the camera compensates by using part of the CCD to the right, then back to the centre.
Optical image stabilisation is also possible, where moving lenses achieve the same effect. This is expensive and normally only used on professional equipment.
Viewfinder/LCD Screen
Digital video cameras have either a viewfinder, and LCD screen or both. A viewfinder is normally low resolution. An LCD screen can be built into the back of the camera, or fold out from the side. The larger and higher resolution the LCD screen, the better quality pictures you’ll be able to see. A large LCD can be beneficial to playback recorded material when you don’t have immediate access to a TV.
Photo Mode
Some camcorders include a photo mode, where a still picture is captured rather than a moving image. These tend to be lower quality than low end modern still cameras, so should not normally be considered as a replacement, more as a convenience.
Audio Dubbing
Audio dubbing is the ability to replace the audio track of a previously shot sequence. This can be easily achieved by modern PC editing software.
Manual Focus
Camcorders normally have automatic focus. Manual focus can be used if you want to achieve special effects, but most users will wan to use automatic focus most of the time.
Manual White Balance
Under different lighting conditions the human eye perceives different colour as white. White balance refers to the how the camcorder mimics this behaviour so that colour appear natural when played back. Manual white balance allows the suer to override the cameras automatic mode, sometime giving more natural looking colours.
Backlight Compensation
Where a subject is standing in front of a light background, perhaps in front of a window, they will often appear dark. Backlight compensation allows the brightness of the recorded image to be increased to avoid this effect.
3 CCD/ CMOS
A CCD or CMOS device is the part of the video camera that captures the image. A 3 CCD or 3 CMOS camera has 3 seperate devices, one for each primary light colour (red, green, blue). These give a higher quality picture, but are more expensive and tend to only be used on professional equipment.
Top Shutter Speed
The shutter speed represents how long the CCD is exposed to light before the image is read out of it. A fast shutter speed will allow faster motion to be captured without blurring.
Minimum Light
The minimum light performace of a video camera may be important. If you intend shooting in low light conditions, then you want a low minimum light figure. Video cameras often perform poorly in low light conditions, using digital gain to brighten the recorded image, with resulting increase in noise (speckles) on the picture.