 What's the Difference Between Analogue and Digital?
Formally an analogue signal is continuously variable and a digital signal is quantised into discrete steps. We therefore get the concept of resolution, which is all about how small you can make the steps. An analogue signal has no steps, but will be subject to small random variations due to noise.
Which Means What in Practical Terms?Media production is technically a series of stages. From the time the image enters a camera until the time somebody views it there is inevitably various editing, post-production and distribution stages. This is an important difference in digital/analogue. So analogue has 'noise' (meaning tiny random corruptions to the signal) inherent in all these stages. When copying analogue from camera to editing facility, from tape to tape and so on this 'noise' inevitably creeps in. This means that the quality of the picture becomes compromised. More expensive equipment can compensate for some of this, but there is always some degrading of quality. So in an analogue system (e.g. vinyl record) the signal played back will not be identical to the original. It will be distorted, and it will include more noise at each stage of duplication and processing. Digital on the other hand, because it's signal can be represented (usually, but not always, in binary a.k.a 0 and 1) as numbers. As the numbers are being copied, error correction ensures that these numbers are exactly the same as the numbers that were recorded on the disk, back at the recording studio. This means the quality will remain the same with each copy.
So Why are DV Cameras Different From Normal Ones as They Both Seem to Use Magnetic Tape? The magnetic tape is exactly the same as analogue (VHS, Beta, V2000) tape. And the same as the coating on floppy disks and half-inch reel-to-reel computer tape from the mainframes of the 1970s, for that matter.
The way the recording is made differs in DV. A digital (binary, in this case) recording is made of the vast stream of numbers coming from the digital video camera. Once again, error detection and correction ensures that the exact same numbers are played back. In an analogue system, the played-back signal would be degraded by the introduction of noise and the slight distortions which are inevitable. However that said, you are now seeing cameras using alternative recording devices to recorded direct to a computer-compatible non-tape device, such as Sony's Memory Stick. So What Are the Advantages and Disadvantages of Each? | | Digital | Analogue | Quality | Digital provides a very high quality picture. Many modern cameras record at broadcast quality. Can be copied without quality loss. | 35mm Film still has powerful quality. While other format such as VHS have very low quality of image. Cannot be copied easily without quality loss. | Cost | Getting cheaper all the time. An entry-level camcorder can be purchased from $600/£800 or so. | 35mm is incredibly expensive, not just to buy - but to develop, process etc. Older technology such as VHS, Hi8 is now very cheap 2nd hand. | Knowledge Base | Being a new technology, many of the issues with it are still being ironed out. For example editing on a home PC can still be problematic as most computers are simply not powerful enough to cope. | An older technology, so knowledge about its use is available and easy to find. | Editing | An evolving technology with much promise. Once footage is in digital format allows non-linear editing, thus opening up more creative avenues. When footage is digital allows the creator to look to other digital avenues such as the Internet. | If edited in analogue, must be done linearly. It can be easier to get hold of basic VHS editing facilities, but limits the process. Most serious editing involves converting the analogue footage into digital
| Further Information Lecture Notes on Technical Aspects of the differences
http://www.chstm.man.ac.uk/teaching/hs228_61.htm
plugincinema on Digital Cinema by Philip Wood |
