Low light CCTV?

For what point exactly? If something moves, I suspect you want to be able to see it?

Reply to
Jimk
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Hi all,

I was looking into a very basic domestic CCTV solution. I already have a variety of gear to play with (old cameras, external enclosures, DVR's etc) but am specifically interested in the very low light cameras.

I believe some here have mentioned the NiteDevil range but reading around seems to suggest that these sort of low light cameras (as opposed to high-end / military I suspect) achieve such with fairly long shutter times and so are prone to blurring / smearing on any moving objects?

If that *is* likely to be an issue, IR would be ok as there is nothing reflective, as could be basic PIR LED lamps to generally illuminate the scene.

I don't have a specific target / scenario in mind, just that the std IR illumination with colour during the day and b/w at night must be the norm for good reason?

Cheers, T i m

Reply to
T i m

I have a starlight camera and yes they blur on moving objects.

It doesn't use long shutter times but integrates many frames (512 max I think).

I don't use it as a security cam.

The PIR light is probably the best if the camera can switch to daytime colour fast enough.

Reply to
invalid

The sensors in digital cameras/phones can see IR up to around 1.1um although most may have a filter to exclude the near IR band. Point your phone camera at the output of your TV remote and press any button and probably you will see the IR LED flashing. Iphones may have a IR filter on the back camera but possibly not on the front camera.

Military IR cameras operate in the 3um to 5um band or the 8 to 12/14um band. Cameras fitted to the police helicopters are probably the latter. With these cameras no additional illumination is required. These cameras do not have glass lenses because glass blocks the IR in these bands.

The domestic CCTV cameras you can buy will be optimised for the visible band but have response into the near IR band (1.1um). IR has no colour hence B&W video output. So basically you are operating the camera just outside the visible band and in low light hence longer exposure times, frame to frame integration over a period of time or additional illumination (in the IR band)

If you have an old digital camera and you want to experiment

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or

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Try it on a very cheap web cam.

If you have any processed colour film negatives around the bits at the end that are completely black can be used as the filter instead of of the Congo Blue filters mentioned in the above article. You could use two bits(double thickness) of this black negative as a stronger filter.

Reply to
alan_m
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Thanks.

Sure ... but that worked as a practical overview of *why* it happens. ;-)

Ok.

... depending on how long the subject is there to view or how much footage (can I say that or should I say 'megabytes of video data' <g>) you have captured to review?

I would like a Starlight camera to play with but not sure if there any VFM models worth having (I believe my recorder (Alien MEGAHero) supports 1080p FWIW).

Cheers, T i m

Reply to
T i m

Nothing reflective that you can see with visible light. Vegetation reflects far more IR than it does red and blue light (which is why it appears green). Grass verges look snow covered under IR.

If the camera switches fast enough and you can get the light levels high enough. Also bear in mind any shadows or areas of lower illumination are going to be dark or just black.

IR illumination avoids any camera mode switching, though there will be a exposure issue if when you switch the IR on/off. Leaving the IR on at low light levels is best. The camera is running at or near maximum sensitivity so lower illuminated areas aren't completely black.

"Colour" is defined the frequency of the lightwaves, so as IR is outside the the range of frequencies of visible light it has no colour. One can of course transpose a range of IR frequencies into the visible range and create "false colour" images, as some thermal image cameras do.

How covert do you want to be? 850 nm (ish) ("near infrared") IR illuminators are visible as dull red glow. If you shift to 960 nm (ish) the source is not visible but the sensitivity of most cameras is noticably falling off by then.

Reply to
Dave Liquorice

Ones using Sony chips tend to have the lowest noise and best performance in the dark. Cameras intended for industrial machine vision or amateur astronomy have the ultimate lowest readout noise and dark sensitivity for a price - however you have to trade number of pixels to get it.

Starlight is one variety of Sony CCTV camera using the latest generation chips that will with the right fast lens come close to what you want. You will end up paying a lot extra for a fast wide angle lens to get the ultimate in low light video capability. To get an idea of what they can do have a look at this video:

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Skip to the second half for low light video performance of the various common chips (unless you enjoy mind numbing musak). One trick they often use is to bin 2x2 or 4x4 pixels to boost signal to noise in low light.

This one compares an iphone 6S, camera and two starlight ones followed by a random promotional video which may or may not be interesting.

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There are PIR near IR LED illuminators as well as some security LED lamps that are sufficiently not far IR that I can see them by their ~700nm tail of emission which the eye can see as deep red.

You can trade signal to noise by averaging over the pixels to get a better monochrome image instead of a poxy looking noisy colour one. Same applies to stereo vs mono audio when the signal is marginal.

There are certainly sensors about now when coupled with the right lens that will give colour video images by the light of the moon. This is one area where you do get what you pay for (although overpriced tat exists).

Reply to
Martin Brown

It's because there's little or no light.

and the sensor isnl;t sensitive enough to 'see' the light.

Star light camera to me, means the 'camera' has to have an image intensifier attached to it, these can be expensive, the sort of thing you'll get in military binocluars and gun sights. Modern smartphones can use clever algorithims to artificaly lighten a subject.

The othe roption is to illuminate the subject with a IR lamp, this is the sort of thing they use for security cameras.

Not sure which would be easist to set up for what yuo want to do, but here they do describe things a little better than purhaps I have.

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Reply to
whisky-dave

Are these the things you can hear clicking in and out if you put your finger over the light sensor?

Yup. Used that as a remote control basic functionality test many times. ;-)

I don't like / use iPhones.

Ok.

Although the SX-16 'Nightsun' could be handy?

Oh, so plastic then, something more exotic or no physical lens as such?

Check.

Check.

Interesting, thanks.

Good idea.

I should have some somewhere.

Cool, thanks.

Can you still get b/w cctv cameras and if so, might they perform better at night than yer typical colour / b/w camera?

Cheers, T i m

Reply to
T i m

More exotic - Germanium lens is common.

Reply to
alan_m

The shutter speed is limited by the frame rate. These cameras store successive frames then combine them. It's adjustable (everything on NightDevils is adjustable) so you can get optimum setting for your application. The most extreme setting gives still pictures in near total darkness that look like day, but anything moving faster than a council workman looks like a ghostly apparition!

Look at

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the picture captioned 'Although this shot appears to be well lit it?s actually quite dark out there!' That isn't an example of real extreme low light, but if you went out there you'd find it very dark.

Bill

Reply to
Bill Wright

Ah, that's true. Maybe I meant not synthetically retro-reflective, like a car number plate?

I have played a bit with a mates system with a mix of different cameras and you can see the system adjusting the light balance after say a car has gone past at night with it's headlights on.

Another good point. Mate has multiple IR LED equipped pointing in a range of directions so as long as the cameras aren't being swamped with light (car headlights) they seem to expose most areas pretty well.

I think mate discussed the idea of an 'IR floodlight'. Could that be better than using the IR illumination in the cameras themselves or could just turning them down be better?

OK.

Seen.

Not at all specifically, it was more of the thought of being able to determine colour (as our eyes define it) at lower levels of ambient light.

Noted (on my mates cameras and one I setup for our daughter [1]).

I wonder if you 'masked' an IR light with a visible one, would that help or hinder most CCTV cameras (at night obviously)?

By that I mean a fairly low level PIR Led floodlight alongside a higher power IR one (also on a PIR possibly)?

Cheers, T i m

[1] I had an old CCTV DVR and a couple of old colour CCTV cameras and I set one up looking out of a first floor flat window overlooking her car in the carpark. During the day everything worked as expected but as night drew on you could slowly see the IR LEDs surrounding the lens in the reflection in the window. So I cut some circular blanking rings and stuck them over the LEDS and because I believe they had Sony CCD's (that seemed to work well in low light), you could still see everything pretty clearly at night because there were a couple of bulkhead lights that were on dusk to dawn that were reasonably bright. ;-)
Reply to
T i m

I think that's what I have (as mentioned elsewhere) and they did seem pretty good (to my untrained eye) under pretty low light conditions. They were quite old so only low(ish?) res at 720 or so?

Ah, ok.

Interesting.

I assume they were all using their own built in IR LEDS and so I would have like to seen them side by side using a common external IR light source, so as to get a more accurate comparison of the actual lens / CCD etc?

Thanks.

Seen.

Interesting.

I guessed that might be the case. ;-)

Quite and something I'm keen to avoid and hence why I asked here. ;-)

For food for thought.

Cheers, T i m

Reply to
T i m

You might want to ask the question on sci.astro.amateur too and take a look at the unconventional use of webcams for astronomy on the QCUIAG site (true DIY stuff using and adapting cheap webcams)

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There is a lot of interesting low light stuff there.

Reply to
Martin Brown

Or *is* the frame rate in the case of these 'cameras'. ;-)

Makes sense.

Ah, that's good to know.

Hehe.

This one:

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I think I saw that before and agree that's a pretty good image. ;-)

So, for a scenario as per the picture linked above, would we be looking at something like this:

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CAM341 or 348 with suitable lens)?

Cheers, T i m

Reply to
T i m
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I like this:

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I do miss making up electronics projects. Some of that has been taken away via microcontrollers etc (and I'm better with a soldering iron than I am an IDE). ;-(

Cheers, T i m

Reply to
T i m

That would be a really big challenge because in order to see light as our eyes define it, that light has to be present in the light source illuminating the objects you wish to see. I remmeber it from physics regarding addictive and subtractive lighting, primary and secondary colours.

another option might be to have a low intensity search light on an automatic pattern of movement that covers the area you wish to view.

Reply to
whisky-dave

ambient

Which in the case of star or moon light it is. It's our eyes that can't work in colour at low light levels and transition from using the cones (colour) to rods (monochrome). Also bear in mind that the central area of our vision is exclusively cones so if you want to see something in low light levels don't look directly at it but 15 to 20 degress away so the image is formed on the retina where the maximum number of rods are.

See thes colour moon lit images:

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Yes the gamma has been tweaked but not the colour balance.

Reply to
Dave Liquorice

In astronomy the low intensity object is tracked so it always occupies the same pixel on the camaras sensor allowing for long exposures or for the combination of many frames. You can do the same with any CCTV camera attached to your house assuming that everything in the scene remains static.

Reply to
alan_m

So.

as I said yuo need light of teh corect wavelenghs in order to see colour.

You can''t just shine a IR floodlight and get true colour night photos.

But this wasn't taken by a CCTV camera was it ?

I;ve seen pictures taken by the hubble that have exposure times of 20 days.

Reply to
whisky-dave

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