is it the sensor or lens that picks up IR ?

[vibe 0]

Learning more every week now, thanks for all the help.

 

Here's my newest question:

 

Even if a lens isn't specifically built for IR, it should still allow a sensor to capture some IR right? As long as there isn't a coating to block IR?

 

Here's why I ask - I am trying out my first real box CCD camera - a low end, generic TDN camera. Awesome picture during the day. At night it definitely goes into B&W mode and definitely gives a better quality picture than my old board cmos.

 

But the old board cmos definitely picked up IR at night. People stood out, the white lines in the parking lot really reflected - foliage definitely reflected as white.

 

The box camera does not seem to see the IR. Right now I am using a lens that was probably meant for indoor use but it does not seem to have any coatings that would block IR.

 

Compare the two screen caps (sorry they are from the quad view so the res is low but you get the idea).

 

This lighter one is a cmos sensor 380-420 lines, see all the IR?

 

This darker one is the TDN with 480 lines. But no apparent IR?

 

 

Happy to learn whatever insight you can give me - does the TDN box just not have an IR sensor - or is it the lens? Shouldn't all sensors pickup some IR? Should I risk disassembling it to look for any additional IR filter even though it has a mechanial IR-cut filter?

[SEANHAWG 1]

Are you shining any IR light for the camera to pick up on? More than likely your old CMOS camera had IR leds surrounding the lens. It is possible that your newer box camera does have an IR filter on it it but the only way to tell is to put an IR illuminator in its field of view to see if it "picks up on that" You can always try using the lights on your old CMOS camera as a make shift illuminator for now.

 

And the IR is captured at the camera's CCD. IR lenses help but are not required for your camera to see IR. The main thing is if there is a IR filter in front of your CCD which would determine if your camera can see IR or not.

[Soundy 1]

CCD and CMOS sensors *always* pick up IR light... color cameras usually add an IR cut filter in front of the sensor to block the IR, because it can negatively affect exposure and color balance.

 

B&W cameras generally don't use cut filters because color balance isn't an issue, and they can take advantage of the extra light collected at night (there's all sorts of "ambient" IR lighting in many scenes, just as there is "ambient" visible light). That's why a B&W camera will usually have better low-light response than color cameras.

 

Cheap day/night color cameras usually have no cut filter, and merely correct the color (as best they can) electronically.

 

A "true day/night" camera uses a mechanically movable IR cut filter that sits in front of the sensor in "day/color" mode, and flips out of the way when the camera goes to "night/B&W" mode.

 

Lenses (particularly the larger C/CS-mount lenses, like on your box camera) typically DO NOT have cut filters. When you see an "IR lens", that generally means the lens is designed to be "IR corrected". Because of its wavelength, IR light focuses a little shorter than visible light - that is, when you focus for visible light, the point of focus of the IR light will be slightly in front of the sensor. As a result, when the camera goes to "night" mode and moves the cut filter out of the way, the IR portion of the light will be out of focus, resulting in a partially fuzzy image. "IR corrected" lenses, through optics or coatings, force the IR to focus at the same plane as the visible light.

[vibe 0]

I've been reading up a bit and it's plausible that the cmos sensor was picking up some IR light at a different wavelength from the streetlights (very old school, I am sure they have some unintentional IR in there)

 

Where the CCD only picks up IR much closer to visible light.

 

For now it's the only explanation I have.

 

I've put up a second camera with a different lens that gets far more of the streetlight so I'll see what happens tonight.

 

I'll say one thing, 480TVL with these big (made in japan) lenses gives me a much better picture than the old 380-420TVL and M12 lenses (even with a high quality M12 lens).

 

Can't wait until megapixel IP cameras are more affordable, all digital over ethernet is definitely the way to go, analog almost seems silly these days but it sure is cheap.

[vin2install 0]

Are you sure the ccd box camera you just bought is truly a TDN?

Do you see the ICR when you are looking at the sensor?

[Soundy 1]

^This.

 

It's also possible the ICR isn't functioning. Most TDN cameras, there should a noticeable "click" when switching between day and night modes. (I'd meant to mention that earlier, but got distracted).

[mike_va 0]

I've put up a second camera with a different lens that gets far more of the streetlight so I'll see what happens tonight.

 

I'll say one thing, 480TVL with these big (made in japan) lenses gives me a much better picture than the old 380-420TVL and M12 lenses (even with a high quality M12 lens).

 

Can't wait until megapixel IP cameras are more affordable, all digital over ethernet is definitely the way to go, analog almost seems silly these days but it sure is cheap.

Using a low f number lens also helps.

 

MP (Arecont, Axis tried) don't have the sensitivity of the best CCD...yet. That is what I am waiting for. Hard to beat the Axis in daylight compared to analog, they are great at setting the exposure/shutter. It would be helpful if these vendors did not spec at low shutter speeds...or made clear what they were doing.

[rory 0]

Both images look horrible.

Are you sure the first one is not a Color IR camera? What type of camera is it?

Neither look like they have any IR in the image anyway.

2nd one is missing part of the bush on the right that would have some light on it as in the first image.

[vibe 0]

I can definitely hear the ICR kick in, it's a short little motor whirl sound as it goes from color to b&w (or back).

 

The m12 lenses were f2.0 but I think these CS ones are F1.6 (I think).

 

I'll try pointing a remote at the cameras tonight or this weekend and see it lights up on the IR (I also have a illuminator but it's a pain to hookup right now).

[vibe 0]

Both images look horrible.

Are you sure the first one is not a Color IR camera? What type of camera is it?

Neither look like they have any IR in the image anyway.

2nd one is missing part of the bush on the right that would have some light on it as in the first image.

 

Yeah part of the bad image is that it's a capture off the quad view and not full view, and it's off a TV capture card, so double the noise. Looks much better in person and recording playback.

 

The first one (board camera) is definitely IR because it's ghostly white during the day with super-muted colors. It can also see things at night like a person walking across a completely dark background.

 

I'll see what happens tonight now that I have two of the same to compare pointing towards different pools of streetlight.

 

Like I said before, my uneducated guess is there is different IR sensitivity on the CCD sensor where the streetlight IR spillover just isn't in the CCD's range. The CMOS was more sensitive to whatever wavelength that was. The only other possibility is that either the lens has an anti-IR coating (which I highly doubt).

[rory 0]

What I was trying to find out, what type of camera is the first one?

A bullet camera with Infrared LEDs??

 

The box camera is probably not a Day Night camera.

You could open it up and look for the IR Cut filter, but you could end up damaging at least the IR cut filter by removing it.

Some cameras will switch to BW but still have fixed IR cut filter so wont pick up any IR, those are not Day Night cameras, although they could be if they were left without an IR cut filter (washed out colors) or included the IR Cut mechanism (more expensive). Digital day night cameras have no IR Cut filter similar to a Color IR bullet/dome, they somewhat enhance the colors digitally.

 

If its a TDN camera the mechanism will be inside the camera casing.

Just because they advertise it as a TDN, doesnt mean it really is.

The switch to BW is separate from the IR Cut filter BTW.

[vibe 0]

Sun has set and tonight it seems to be working much better.

 

Right at sunset the motors whirled, picture banked for a second and then it was b&W.

 

Earlier I discovered I had white-balance turned off - turning it on seems to make a difference.

 

Old streetlight is definitely producing IR, the second camera is pointing towards it and objects directly under it are all glowy and there's enough light as if it's daytime (but b&w).

 

The second camera is also using a different brand varifocal lens. It makes me wonder if the first lens does indeed have some kind of mild anti-IR filter coating. I got these off ebay used and they are randomly selected from a batch, I am going to try to get more next week to experiment with.

 

Picture from both cameras are much, much more useful than my old m12 cmos board cameras.