security cameras

[boily]

i am looking to buy a couple of security cameras but I have a query what does it mean when you have a 4mm lens and say a 9mm lens i am looking for a camera that does long distance and where abouts in the se of melb to buy them.
thanks

[watchdog]

depends what distance your taking about. I recently did one with x120 optical/ digital zoom. When we took it to the extreme (x120) it made a really good earthquake detector. This thing was mounted to a solid concrete wall but at those distances a truck driving by causes enough vibration to make the picture useless. Luckily we didn't need to operate it at x120

[boily]

I found a camera on the web there are 2 one has a vari focal lens 4-9mm the other has a vari focal lens 9-22mm which one would be better for long distance viewing
thanks

[global88]

Just be careful of the chineese waterproof cameras. Bought 2 infared ones, fitted them under eaves and first good hard rain a couple of weeks ago proved their not so waterproof.
They have dried out but still "shake" on screen.
The end result is the movement on screen causes over recording.

[konstask]

is there a camera that it's not made in China?
Now days it's hard to find a camera that it's all parts, made not from China.
But I don't have a faulty Chinese camera.

[global88]

yep konstask yourve got a good point there.

had a play with my system today only to find that i was wrong, my cameras are fine, its the dvr card. (made in china)

[intelliGEORGE]

I found a camera on the web there are 2 one has a vari focal lens 4-9mm the other has a vari focal lens 9-22mm which one would be better for long distance viewing
thanks

Lens' size mean nothing unless you know what you want to view.

The question is not which is better? Because for different scenarios each lens has its pros and cons, what you need to do is work out what you want to see.

When you have established this, you then need to know how far the object is and how wide or high the object is. For eg.

You have a 30 meter long drive way and the gate at the end you want to see is 4.5m wide and the camera you are using has a 1/3" CCD.

Apply this formula when the length and width are known;

F = 4.8mm (CCD Horizontal) X 30m (Length) / 4.5m (Width)
F = 32mm

Therefore the lens required to see the scene is a 32mm lens.

Apply this formula when the length and height are known;

F = 3.6mm (CCD Vertical) X 30m (Length) / 3m (High)
F = 36mm

A standard 1/3" CCD's dimensions are 4.8mm H x 3.6mm W.