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[Travelmate]

Hi!

I'm using one of my 942L cameras for monitoring a narrow external corridor. Just tested the 942L with the mentioned external illuminators with a subject at 8m distance

1) 30m distance 850nm visible external IR illuminator. It glows like a red LED traffic light in the dark and the subject is clearly visible. However, if at about 4m away then the subject becomes too bright i.e. like looking at an overexposed photo

2) 25m distance 940nm invisible external IR illuminator. No red glow but subject not as bright and not clearly visible as the 850nm type at 8m distance.

Bought the 940nm IR invisible illuminator, which is more expensive, from below

http://www.camera2000.com/en/catalogsearch/result/?q=940nm+ir+illuminator&x=23&y=14


I believe I must have bought an underpowered 940nm IR illuminator. So, does anyone knows if I want to get the the same brightness as the 850nm type at 8m subject distance what equivalent 940nm should I buy i.e. should I buy one good at 50m or at 100m? Any link on the net to show the equivalent illumination power between the 850nm and 940nm IR illuminators?

Thanks  

[brian5]

Here is some general info that I've found, hopefully it's of use.  It talks a little about the response at different wavelengths.
http://www.cctv-information.co.uk/i/Infra_Red_Illumination

I would think you'd need detail about the cameras ccd itself to make a suitable choice.

[Travelmate]

Here is some general info that I've found, hopefully it's of use.  It talks a little about the response at different wavelengths.
http://www.cctv-information.co.uk/i/Infra_Red_Illumination

I would think you'd need detail about the cameras ccd itself to make a suitable choice.

Hi thanks for the link

I've read it but it's really beyond my comprehension. At any rate after searching the net for some simple answers I came across a simple rule which says you'll require 2 - 3 times the illumination power for the 950nm invisible IR over the 850nm visible IR.

Normally, those day/night IP cameras for home use come with the cheaper and more common 850nm red LEDs. And the 940nm invisible external IR illuminator will work best with the camera that's sensitive to the 940nm IR.

So, in may case, to extend the night visibility of my 942L (which is designed for 850nm) at a subject distance of 8m I'll probably need an invisible external IR illuminator of say 80m which is going to be big and costly too.

 

[JavaLawyer]

By popular demand, I drafted the following FAQ post to describing the basics of an external IR illuminator: DCS Network Cameras - Improving Night Mode with an External IR Illuminator

If you have additional information that could improve upon this post or see any glaring errors, please let me know and I'll make the appropriate changes.