1. Choose CCD chip
some guys like cheap Cmos chip camera. But as an expereiced security camera seller and installer, i suggest you to choose CCD chip camera. even 1/4' Sharp chip cam will be much better than Cmos. and Sharp is only a few bulks more expensive.
2. Choose the correct lens
to monitor the door entry, a wide view angle lens is more fitting. -- so , 3.6mm is better choice.
3.6mm -- 80 deg
6mm -- 60 deg
8mm - 40 deg.
3.6mm -- 90 deg
6mm -- 70 deg
8mm - 50 deg.
3. Day/Night cameras
with IR leds. -- still will not be able to work in completed dark -- besides it needs solid object to reflect the IR lights.
but most infrared cameras are good for home use. They are color at day time, turn to black/white when light is not enough
1. PC based record -- dvr card
software compression cards save money, but it depends on computer too much. Sometimes there are a lot of problems could not be resolved at all... kinda annoying. but if you are a computer geer, go ahead for this kinda stuff ;-) when you beat them, they delight you very much!
Hardware compression cards are good. But their price is almost equal to a standalone DVR.
2. Standalone DVR
not as expensive as before ^_^ . Most of the standalone DVR nowadays are for home use. There is no professional knowleadge required. Highly recommend for DIY fans.
Wired system are much better signaled. But to wire is troublesome to most of us i believe. To video wire the cam, to power leads the cam...
Now there is All-in-one cables -- siamese cables , or we say, video/power combined cables. That make things a little easy.
--- How about wireless system?
Remember the news that a mother received the NASA video from her baby monitor? That was the Wireless! Haha.
The signal is very easy to be interrupted. Unless there is more painful to wire than to receive what you dont want to see, we do like you to buy Wired system.