Very grainy image in low light

[Numb-nuts 1]

I have two cameras covering my portico at home, one B&W and the other is colour.

At night they are supported by a lw ebergy light that gives sufficient light to see any

subject, but I have noticed the pictures are extremely grainy.

Both cameras give a sharp crisp picture in natural light.

 

Can anyone suggest what this might be due to and what I might do to improve the night vision.

I have already ordered a IR floodlight to cover the area beyond the portico and to add some light

in the portico but is there something else I should be trying?

 

Many thanks for any suggestions...

[ptzguy 0]

What's the brand and model#'s of the cams?

Do they have DNR/SSNR settings??

What is the Lux capability of them both??

[rory 0]

What are the lights/bulbs used?

What type of cameras are they?

[Soundy 1]

In general... the noise is caused by the camera electronically boosting a very dark signal. The noise is always there at a very low level, but with lots of light, you don't see it.

 

Adding IR probably won't help the color camera's performance, as it's likely got an IR cut filter (unless it's a day/night model).

[Numb-nuts 1]

The B&W camera is an Eneo VK-1317S Board Camera with 3.8 mm lens and fixed Iris,

I choose this because it has a 600TVL rating and the need for colour was overridden by the need for

a clearer picture, and so far it ha sbeen fine apart from the graininess in low light.

I have plans to add more light since the area it monitors is backlit by daylight during the day and street lighting at night.

 

I have to be quite honest that I have no idea about the other camera. It's a door-view camera not a cheap one,

with wide angle lens (2.5) and doesn't appear to have an IR cut filter because even in low light

there are traces of colour. I have plans to replace this with a high res 600TVL B&W bullet camera when I can figure out howI will

mount it.

 

It is interesting that the graininess (Noise) is always there but can't be seen during the day, presumably because of the quality of natural light?

You say it's the camera trying to boost the picture and being asked what the lighting is, I have a clue my problem is down to the lighting and wether or not it is sufficient for purpose? I suspect not.

 

I use a low energy light bulb in a bulkhead light housing through the night and suspect that this is not sufficient although it has worked

 

reasonably well so far. I will tray a brighter more a natural light bulb and report back the result.

 

Thanks for your responses so far guys.

[Soundy 1]

I have to be quite honest that I have no idea about the other camera. It's a door-view camera not a cheap one, with wide angle lens (2.5) and doesn't appear to have an IR cut filter because even in low light there are traces of colour.

That means nothing. Unless it's a "cheap" day/night camera, almost all color cameras have IR cut filters. "Traces of color" are probably compression artifacts generated in your DVR.

 

It is interesting that the graininess (Noise) is always there but can't be seen during the day, presumably because of the quality of natural light?

You say it's the camera trying to boost the picture and being asked what the lighting is, I have a clue my problem is down to the lighting and wether or not it is sufficient for purpose? I suspect not.

It's nothing to do with "quality of light," just the amount of it.

 

The noise is electrical noise - always present in the sensor, but at a very very low level (so it's normally "dark"). When the image is bright, the noise is at a minuscule *relative* level (you might see a bit if you zoom in on a black area). When the image is dark, the camera electronics compensate by boosting the signal level... which brings up the dim parts of the image, and the noise as well.

 

If you're old enough to have played with cassette tapes... imagine you're playing a blank tape, and normally you hear nothing, until you turn it up REALLY LOUD, until you can hear the hiss from the tape (small levels of latent magnetism, in this case). If your music is at a suitable level, you won't hear the noise, because you have to turn the overall level down... if the music is very quiet, you have to turn the volume up more, and you'll hear more of the hiss underneath the music.

 

This is almost exactly the same thing that's causing image noise in your camera at low light.

[rory 0]

The B&W camera is an Eneo VK-1317S Board Camera with 3.8 mm lens and fixed Iris,

I choose this because it has a 600TVL rating and the need for colour was overridden by the need for

a clearer picture, and so far it ha sbeen fine apart from the graininess in low light.

I have plans to add more light since the area it monitors is backlit by daylight during the day and street lighting at night.

 

I checked online and the specs say 2.1Lux, or 0.75 lux, which is not very low light either way, so it will be compensating under anything less. I will give an example of KT&C BW Bullets I tested briefly in a night club under dark conditions looking at the dance floor with no lights on the dance floor at all, and just some low powered lights behind the camera.

 

The lux levels are just an example, to give you the idea of how the high res, standard res, and exview chips vary in low light from BW cameras.

 

A-BW 600TVL 0.1 lux

B-BW 420TVL 0.05 lux

C-BW 600TVL Exview 0.03 lux

D-BW 420TVL Exview 0.003 lux

 

Basically © was not as grainy as (B), and was sharper.

(A) was the darkest, needs the most light.

(D) performed the best though was not quite as sharp.

Overall © is a good balance, but the camera is the same price of (D) and twice the price of (B).

 

Summary: (in this case)

The lower resolution camera of the same chip type and features will outperform the higher resolution under the same low light condition.

 

Once again, this is just from brief testing and may not be 100% correct, though if you check the specs of a 600TVL BW camera and its 420TVL version, you should see the 420TVL has a lower lux level, and this has been evident in testing. Eg. http://www.ktnc.co.kr/english/viewtopic.php?t=395

[Numb-nuts 1]

That is very interesting. I won't pretend to fully understand straight off, but if I take a little time

to read and understand that correctly, I am sure it will be of great help in understanding the problem.

[rory 0]

Bottom line, if you still want 600TVL BW, add more light or change the bulb, and/or get an Exview 600TVL BW camera.

 

Even then though if the light falls below the minimum lux level of the Exview camera, there would still be noise.

[Numb-nuts 1]

Ive had a bit more of a think about your tests and looked at the bullet cam I am going to replace my color door-view camera with.

It is a 600TVL with IR sensitivity of just 0.005 lux, the sensor is a 1/3 inch Ex-view HAD CCD.

Having read your post, I am confident it will at least be better than what I have now and stand

a good chance of giving me the best of all round performance in the circumstances.

 

With regards to my existing light. I have decided to move it's position slightly and to replace the bulb as suggested.

 

I have also bought a 12 LED IR board on ebay, and found a dummy dome camera in a thrift shop for £1.00

I have now fitted the board to the dummy dome and have a cheap IR illuminator. (Not very professional I know)

I can fit it on the portico ceiling and see what kind of result I get.

 

I originally wanted to fit the IR board into my corner camera housing but cannot figure our how to

effectively blinker the lens from the IR light so I didn't use it for that because the camera would see

only the reflection of the IR.

[ptzguy 0]

Hi again Numbnuts,

You have a supplier there in Manchester that sell ShadowView cameras, having installed them many times I can safely say they are quality.

 

Spec.

550TVL Sony CCD

True colour or Day/Night selectable

2.8-11mm varifocal lens

0.00045 Lux with sense up

On screen display (OSD)

Test video output

4 Masking zones

Aluminium external housing

Colour: Black or White

IP65 Weather proof housing

3-Axis rotation

Power input: 12v DC 95mA

C/W 800mm cable with BNC & DC jack connectors

Size: Ø 105 x 140mm

 

0.00045 Lux - if there's no twilight you only need a candle!