Best Way To Stop Light Changes!

[dsw]

Hi guys,

This might sound daft but can anyone recommend some good body cameras that work well under artificial tube lighting. The last lot of cameras we have installed (all sony chips) up to 520 TVL have had problems with artificial light. The picture goes from like a dark orange to a light white colour constanly changing but only under this type of lighting. Some cameras are worse than others. I know probably an expensive JVC camera would sort this out but can anyone recommend a camera at around the 120 pounds mark that wouldn't be so affected and produce a good steady image.

Paul

[Rich]

Have you tried different lenses?

[dsw]

Not really. Think they have all been the same. I will try different ones on next install.

[Guest stevey]

Not really. Think they have all been the same. I will try different ones on next install.

This is called hunting, if you play around with some of the advanced settings you can try to eliminate this. Else, baxall do cameras that have options for fluroscent lighting compensation as standard.

[dsw]

I have tried all advanced setting on cameras, agc/blc/awb..... and still cannot solve the problem. When you fastforward a recording you can see the colour changing quite dramatically. Think i will have to try some better cameras next time.

Does any one know how good the Cop day night cameras are. Am not sure wether to try merit lilin next or samsung. Can anyone recommend any cameras from experience at around the 120 is mark.(need to have reasonable low light performance and good res)

Thanks again

Paul

[Doktor Jon]

Jarv,

As a first step, it would certainly be worth trying Alarm Guard's suggestion of fitting a colour temperature correction filter. It costs next to nothing, and at the very least it will eliminate colour temperature as a possible cause of the White Balance circuits misbehaviour.

If it doesn't work .... I have a cunning plan ....

[Rich]

I remember having this problem years ago, and digging about the memory, I seem to recall being told that the frequency of the artificial light was bouncing inside the lense causing the colour unbalance and strobing effect, not sure if that is what is hapening, but I am sure that changing the make of lens corrected the problem.

[dsw]

Thanks again for all your help, i will try a different lens tomorrow.

[Matt the Teckie]

There is actually a very good reason for the camera performing in this way and it's nothing to do with the lens. I'll wager that you're powering the camera using 12vdc.

If this is the case, the camera will be running using its own internal trigger.

Essentially the fluorescent tube never emits a constant colour temperature. At different points on the mains cycle, it will emit a slightly different colour temperature, which in turn will reflected at different temperatures, after absorption by materials within the scene.

Have you ever watch one of those b&w movies where the wagon wheels seem to rotate backwards even though the carriage is moving forwards? This is because the wheel has moved nearly all the way round before the camera takes the next shot.

It's the same kind of scenario here. Each time the camera takes a shot of the scene, the colour temperature has changed slightly. If the video is formed at 25fps, the scene may "appear" to colour drift.

There are only two ways to remedy this situation. The first (and best) way is to power your camera using an AC supply, then line lock it. This ensures that the camera always triggers at the same point on the mains cycle. This being the case, the colour temperature being emitted by the fluorescents at the time that the camera takes the shot will appear constant. The alternative is to introduce some incandescent light into the scene. This method will only lessen the effect.

Hope this helps and good luck

B)

[ian.cant]

Matt i dont dispute or critisise your theory there at all, its not an explanation ive come across before and ive never seen a similar fault either which is where my question comes from.

If your theory is correct then how come it doesnt happen to all DC powered cameras in flourescent lighting situatuations? Ive fitted hundreds of DC fed cameras in such situations without problem?