Replacement lens

[Omaha]

Hi,

I'm a novice, but have decided to use Hikvision Exir Turrets around the exterior of the house. The cameras I've purchased, though, all have the 4mm lens. I was curious if those could be swapped out for 2.8mm lenses? If so, can you point me to a source for the 2.8mm lenses? Thanks,

Om

 

[Kawboy12R]

Yes but don't. Novices tend to want hugely wide fields of view but then get frustrated when something happens and they can't get a good face pic because 2.8mm lenses are basically only good for "what's going on" rather than "who did it" unless the person comes right up to the camera. 4mm is better for ID and not much worse for FOV. You'd be best off picking a job for each camera and either adding the correct lens or, better yet, adding another cam with the correct lens for the job you want. For instance, I consider 6mm a minimum for covering a car parked very close (almost touching) your house. If you MUST get wider coverage from the camera and have a wider field of view, use a 4mm. Depends on the layout, but I have three cameras on the front of my house. One fairly wide angle (3.something mm) above the front door because the people I expect to need to ID with it will be walking right up to it but it also serves as a "what's up" camera for most of the front yard. Another cam on the upper driveway set at about 6mm to cover the one vehicle parked in it that's generally within 8 feet of the house. The front door cam can see that driveway but is absolutely useless for ID at 30-35' away. The lower driveway was good with a 6mm 4mp Hik turret covering a car that's usually parked with the front bumper about 12' from the camera but now has a PTZ covering that car. Lens length gets changed often but is almost always longer than the 5.1mm minimum adjustment.

2.8mm is a good lens if you're on a budget and just want to pay for a few cameras to use for footage to show your insurance company "Look, there it goes!" and give up much hope for a good ID shot. For anything much better, use www.ipvm.com/calculator and plug in the details for your cameras. Change lens lengths in the tool until you get 100ppf (pixels per foot) as a minimum. Also realize that most wide angle cams have a bad hotspot in the center from the built in IR LEDs. That tends to make faces outside the hotspot too dark and turns them completely white when the thief gets into the 100ppf range on a 2.8mm camera unless you have good supplementary lighting like bright floodlights and/or external wide angle IR illuminators.

 

[Omaha]

Kawboy12R,
Thanks for the detailed and well considered reply! This is precisely what I needed to know.

 

[Myllerman]

Yeah good nfo.Until autotracking with zoom is good enough i guess dual cameras is the only way to go for some locations. I have locations that need minimum 90 degree view to spot intruders but as Kawboy stated the resolution / foot aint good. Wide fov is also a pain to illuminate and the cameras dynamic range much cope with alot more so washout is a concern.