foggy image

[stuhar 0]

hi all I have been reading some of the postings and I need a bit of help with my cctv system, I have a 4cam system using a killer 4 channel dvr with a 1GB SAMSUNG HD istalled, 2 cams are of the bullet type with 48led and 480tvl sony ccd the others are ebay dome cams 420 tvl with 24 ir led ,

the problems is the dome ebay ones they give off a foggy picture at night and are basicly useless at night is there any way to rectify this,and is it the ir,s thats causing the problem ,would unpluging the ir board inside the cam have any effect, as we have a street light right where the cams are and maybe I dont need the ir's on, would the cam still work ok , cheers all

[cglaeser 0]

Could be OOF (out of focus). The focus for day light is different than IR. More expensive cameras either try and correct this in the lens or support auto back focus. It's more difficult to do on the cheap. If you can adjust the focus, you might try focusing at night and give up some of the IQ for day images.

 

Best,

Christopher

[tomcctv 188]

hi stuhar. it wont be the focus once focus is set its set. you say you have a street light by your camera ??? this could be a problem......cameras with ir also have to turn b/w at night the street light might just be giving your camera to much light to let it turn b/w ..........so it sounds like your camera is viewing ir with colour which will show bad pic as ir and colour is no good. another problem is over power check your power supply

[cglaeser 0]

it wont be the focus once focus is set its set.

 

How do you know the focus was set for IR?

 

Best,

Christopher

[stuhar 0]

I have set the focus in daylight and the image is clear its hard to do as you have to strip the unit down so you can acces the cam lens, the image at night does go B/W and this is when I get a foggy picture it looks like the lens has got marks of fog as like a refection,the cam body is white to go with the canopy its underneath may be this may be interfering with the spread of the ir's and refecting back to the lens I will try and put some black psu tape around the encloser of the dome to see if the housing is relecting ir light back to the lens.

[tomcctv 188]

like i said once focus is set it is set for day or night. you focus the lens. nothing to do with day or night opperation. so what your saying chris is after every install you have to go back at night to focus the cameras again.

[cglaeser 0]

so what your saying chris is after every install you have to go back at night to focus the cameras again.

 

What I'm saying is that different wavelengths of light have different angles of diffraction. That's why a prism makes a rainbow. The same principle applies to lenses. High-end SLR manufacturers deal with this all the time. The more expensive lenses have exotic multi-element lens designs to ensure that the red shirt is focused with the green grass.

 

However, red and green are relatively close compared to IR. Some SLR lenses have special markings to focus IR, which is different than the markings for visible light.

 

The same principle holds for security cameras. There are several ways to try and solve the problem, including more expensive lens designs and a back focusing system that focuses differently for daylight and IR. In cheaper cameras, you are pretty much on your own. If you have focused for daylight, then the camera will not be focused for IR. In addition, if you have focused for daylight but more to the UV side, IR will be even worse. You have several options. You can focus somewhere between daylight and IR and compromise both, or decide which is more important, sharp daylight images or sharp IR images.

 

My suggestion is focus for IR and see what you get. If you get relatively sharp images, you will know your options.

 

Best,

Christopher

[stuhar 0]

I dont think its to do with focus as the image I can see is foggy but focused there are patches that you can see in the image that are focused but mainly its a foggy apearance I will try and get some images of the dvr and post them to let you see what I am seeing. thanks for all your help I feel I have opened up a can of worms on my 1st post !

[cglaeser 0]

I dont think its to do with focus as the image I can see is foggy but focused there are patches that you can see in the image that are focused

 

Yes, sample images will help, but keep in mind that focus relates to a plane of focus and depending on the DOF (depth of field), you can't necessarily focus everything in a frame. Some areas in focus and some areas out of focus is consistent with the characteristics of focus. Also, OOF (out of focus) IR looks a bit different than OOF daylight. Post some photos for us to review and that should help.

 

Best,

Christopher

[kensplace 0]

back focusing/focus should be done with the iris opened, ie when dark, often people use nuetral density filters to help focus.

 

Is it possible is a reflection of the IR bouncing of the dome/glass?

 

Any chance of those sample pictures?

[mitstarion 0]

You mentioned a foggy appearance on the lens. Try cleaning the glass in front of the lens (part of the camera body) and the lens itself.

[stuhar 0]

I will post pics soon cant do anything on here tried to add them but ftp failed then tried to linki them to 4shared , not enought posts !!! to post link

[stuhar 0]

hopefully it will let me post at least the linkon the next posting

[fisherclive 0]

sounds like ir reflection to me, i've had this problem with domes before.

try using a good quality dome with a very low lux rating or use bullet style cameras