Stuck in the Dark Despite the Light

Note to the Reader: I have combined three separate email letters and one response in this case. Not always easy to answer the first. As usual, I have also changed the name and location of the original mailer (in this case for good reason).

Dear Charlie:

Doubt that you remember me. My name is Dan Dan. I own X X X Security Consultants in the Midwest somewhere. I attended the seminar that you spoke at in Atlanta last February and I also met you at the ASIS Convention in St Louis, MO. It was there that I was introduced to infrared and it all seemed so simple :-)

Now for the problem. I have installed camera system that I am attempting to light by infrared. I bought a led system that supposedly lights up a 120ft by 60 ft area and am using it to light about a 30 ft by 15 ft area. I factored in a safety margin. Problem is this thing does not work. I suspect my cameras (notice plural) are not sensitive enough to 900 nm infrared ... though I was assured by the distributors that they were. The light when you view it through the camera looks like a bright flashlight in the picture..

Guess the question. Have you got a suggestion on a camera to use that would be sensitive to this range of infrared. A make and model is all that is necessary. Lacking that should I go to a lower infrared range? Hate to do this because we are using this to try to bust a Meth lab and it is imperative that the light from this thing is not seen.

Thank you for the prompt response to my questions. Good to hear from you. Actually what is happening is they are stealing anhydrous ammonia out of some tanks to process the stuff. They are basically putting it in quart jars and small coolers and hauling it away. My client (who is a good customer in other areas) wants to catch them before they hurt themselves or somebody else ... Police have their obvious motives. My problem is when I put this in I thought infrared was going to be a snap...ASIS seminar made it sound good, so, instead of making my mistakes in private, I made them in front of God and everybody and yes I feel like I am up against the wall on this thing...never paid much attention to ego, but this one has become a matter of personal reputation..

Note the questions:

1) It looks like a bright spot in the middle of a black void...you can see house lights and car lights in the distance but the scene I am lighting is black..

2) The only 900nm unit I could find that the company had in stock was from an outfit called Super-circuits. I originally ordered that Pelco thing, but, you could see the light and the size of this thing (!!!!!) made it stick out like a sore thumb. This one is in a halogen floodlight housing and works off 12 volts. I put a small supply on it for concealment purposes and noticed yesterday that it had pulled this supply down to 11.7 volts....going to try a bigger supply today. This light cost about 550 bucks and is supposed to be a good one...will get the exact model for you today but I think it is the DS-5..

3) Tried three cameras.. Sony sptm-104, A Panasonic WVP312 and then I called the Super- circuits people back and they sent me one of theirs...Said they used them all the time...I do not know exact model but will get it today too.. Cost of that thing was $89..

4) The light is mounted 28 feet high...the area I am trying to light is 32 feet long by about 15 feet (width of a farm anhydrous tank) wide, the light was supposed to light 120 X 60..I realize that is a rough estimate but I bought it so I would have some safety factor in the project..

I have a little more info that may help on this project..

This light I am using is an infrared light working at 940nm. it is made by Precision Engineering... The Model is the IR-4. The camera I am using is the PC-23C... That was the camera suggested by the distributor that I got the light from... I did get this thing on the bench where I can work with it and talked to the manufacturer...first problem was the camera is not sensitive to 940nm as it could be... Secondly I am using a pinhole lens which is apparently a serious mistake... I corrected the lens problem and it worked a little better...Surprisingly the manufacturer could NOT suggest a camera that is sensitive to 940nm..Have you got any major suggestions...

Guess the other question I have is it possible for a LED light to project out with a usable light 100 ft or so?? Does not seem possible to me..

Finally, are you familiar with this particular illuminator or company?? The engineer that I talked to seemed knowledgeable and helpful... But, you know how that can go...

Thanks for your interest and assistance. Any help you can render would be appreciated. A reply to xxxx.net would be appreciated. If this comes under the heading of consulting please let me know what the fee is. At this point I am getting a little desperate.

Sign me, Still in the Dark in the Midwest

Dear Dark Midwest,

To put things into perspective, I will now try to attempt to falter through some answers for you. I'm going to do my best to make some sense of all of this for you so I will need your feed back if I leave anything out or put something in that doesn't make sense. Oh well, here we go.

First, let's talk about light in general. With every camera, we have a sensitivity rating. This infers as to how much light (on a minimum) that the camera requires to make a minimal, but usable image (1vpp). This sensitivity rating is produced through testing using a light format that is primarily in the visible spectrum. Additionally, the manufacturers produce a spectrum response chart for each camera. The spectrum response chart demonstrates the overall spectrum of light that the camera will see or react to.

What most people don't realize or understand is that there is a sensitivity rating for infrared light as well as visible light. The spectrum response test demonstrate that the camera will see into the infrared spectrum, but does not demonstrate how much intensity of infrared light is needed to produce a usable, 1vpp image. Hence your using a pin hole lens being unsuccessful with your camera under infrared light. The Pin hole lens restricts too much light to be useful. Changing to a standard lens gave you better light passage and so better results under the infrared light. You would have had the same results under minimal visible light.

As for an infrared sensitivity rating for the cameras that you have tried, there is no such animal as printed or tested by the manufacturers. This is because there is a minimal market in this direction and they don't need to or feel like spending the money. They can tell you what range of light their camera will produce an image under (as based upon the spectral response chart), but once you leave the visible light spectrum, they can't tell you how much infrared light (in lumens per square yard) is necessary to produce an image. Consequently, you can have three cameras that are all sensitive in the 940nm spectrum, but each would produce a different amount of video image according to the amount of sensitivity that they have in the infrared spectrum.

As a direct result of the above, a camera may be rated to see 900nm or 950nm light, but no one told you how much light was needed to produce a minimal usable image. If you had this information, you could produce X amounts of lumens of infrared light per square yard to get an image. There is one gentleman in the UK however, that does produce such charts. He actually is the one that spear headed the research necessary to prove the point. I have given you his name and Canadian contact point below so that you can contact him to help you with your dilemma. Please let him know that I referred you when you contact him. Trevor Duffy is, in my opinion, one of the leading authorities in the world on infrared illumination and camera response.