Electronics › Electronics › Difference between digital and analog camera › Not quite sure how far back
Not quite sure how far back you are going in history here! The original analogue camera is the one that uses film but that is not exactly what you are looking for here is it?
Basically, all electronic cameras are based on what is known as a CCD (Charge Coupled Device) and those are tiny circuits that are sensitive to light and in the colour versions, they also pick up the levels of red, green and blue light separately. The size of the chip physically, is not always a good indication of its sensitivity but generally cameras are now graded by the number of pixels they render from the image. It is that information that is digital and then processed to give a required output which could (and often is) analogue. Thus all electronic cameras are digital at the ‘sharp end’, that is the bit that does the sensing because light is actually an analogue waveform, the chip is an ADC (Analogue to Digital Coverter). For your purposes it would be best to have at least 5MP (Mega Pixels) if you want clear images although for close range you may get away with as little as 2MP
The output from a camera can be in digital or analogue format and most that are easily available are analogue output, often including a small microphone, with separate leads for audio (white plug) and video (Yellow plug) plus a power connection. It is possible to get wireless versions but the batteries tend to not last very long and as the whole purpose of a security camera is for it to be difficult to see or tamper with, changing batteries becomes a real problem! It is better to go for a hard-wired system. More expensive versions are split RGB and that can be either in standard analogue or digital, it all depends how much money you have to spend or burn!
For security monitoring, you really need to have a camera with the lowest possible ‘LUX’ rating. This is the camera’s ability to pick up images in low light and also they should be sensitive to infra-red light (IR) at fairly low level. All CCD chips are in fact sensitive to IR but not all do it well. Some cameras are now fitted with a halo of IR LEDs that are effective up to maybe ten meters but if you want to have better range than that at night, there are also IR LED flood lights that make the images look like it was daylight.
The lense is also a major factor. As in any photography, TV, Film etc., a good quality lense will make a lot of difference to the images but having said that, a pin-hole camera for short range is often perfectly adequate, I would use them up to 5 meters but much further than that, face or number-plate recognition requires some magnification and precise focus.
Bottom line? For cost effective monitoring, a good CCTV camera with a LUX level of 0.5, IR LED illumination and a simple video/audio output for a small area will give you a similar quality image to a basic computer web-cam. in fact, that is a digital output at the bottom end of the market and I have seen them used as simple shop CCTV cameras. If you want to use multiple cameras there are add-on boards for computers that will take the analogue camera inputs and record all at the same time. To be honest, it is better to get a dedicated recorder though. Again, here there are variations. Some record in AVI format which takes up a lot of disc space and some in MPEG which takes less space and gives more recording time. Then or course it is possible to have an analogue recorder using VHS tapes but the biggest problem with those is that people tend to re-use the tapes and quality falls dramatically to a point where the recording is pretty useless for any means of indentification. The heads wear, the tapes wear and the cost of maintenance is high.
It’s all really a matter of what the budget avaiable will afford. BUT just spending a lot of money on a top name brand does not mean you get the best quality or best value! Shop around and read the specifications carefully.