newbie need help selecting camera

[Hans007]

Hi folks, i have been reading this forum as quest for some time now. and now as a member, and need some help selecting the right camera.
my first idea was to buy unifi g3 dome camera, but after reading so much in here i feel in love with HIK DS-2CD2142FWD, but i can see that they have this camera in different lens sizes, so my question for you are which lens size should i select, by standard it has a 2.8mm but for the same money i can get them with a 4 or 6 mm lens.

 

[alastairstevenson]

Hi folks, i have been reading this forum as quest for some time now.

The choice is governed by the field of view that you need to cover, and the level of detail vs distance that you require.
For example - do you want to be able to identify people from facial views, or do you want to just want to see an overall view of activity?
Take a look through the many sample stills that members have posted for cameras with those lens focal lengths and you will quickly get an idea of what your choice should be.

 

[Kawboy12R]

Use the ipvm.com/calculator and plug in your cam's specs in and shoot for 100 pixels per foot where you need facial ID. The tool doesn't always match the real world FOV so if you can find the actual FOV from the manufacturer published somewhere then fiddle with either lens length or sensor size choice to make the tool's FOV match up to what is published.

Also, unless you really need a bubble dome and you'll definitely be using the alarm, audio, and/or wifi support of the 2142 then consider a turret format if it'll be used outside. The bubble causes IR bleed and reflection issues, limits the angle with which you can direct the lens and still effectively use the internal IR, plus the EXIR (single LED with a wide angle of dispersion) gives a better, more evenly lit scene at night. Nothing wrong with a bubble dome outdoors in a sheltered location with the internal IR turned off if you really really think you need the bubble over a turret format, but realize that you'll have to supplement with an external illuminator or a dusk til dawn light plus maybe motion lights.

I'd only pick 2.8mm for special close range situations with a wide open view. Particularly outdoors, 4mm is a better choice for higher quality face pics while keeping a wide FOV. I prefer a minimum of 6mm outdoors if I want decent face pics at anything over 15 or 20 feet from the camera. Basically any driveway situation covering cars unless your front bumper is basically touching the wall the camera is mounted on. In direct comparison, 4mm is pretty crappy vs 6mm at 30' at night. 2.8mm compared to 6mm? Forget it.

 

[zero-degrees]

Here is some real visual / real world examples. This may help you.