Subscriber Discussion

IR Cut Filter

UD
Undisclosed Distributor #1
Oct 15, 2016

 

why the image produced by the camera is good in the night time when set to B/W mode , compared to the color mode 

UD
Undisclosed Distributor #1
Oct 15, 2016

my explanation is that the camera blocks the IR filter in the color mode because of which camera cannot produce a good image in the night time ,whereas in the B/W mode the camera allows the IR filter to work ,so we get the good image in the night time ? is it correct ?

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U
Undisclosed #2
Oct 15, 2016
IPVMU Certified

Different wavelengths of light have slightly different focal lengths, even in the visible spectrum, e.g. blue vs red. IR wavelenghts continue where red left off and get even longer.

In the daytime, since IR and visible light are both present in large amounts, this results in not being able to set an optimally sharp focus.

The cut filter filters the IR so the focus can be sharper in the day.

At night we will take any light we can get though!

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UD
Undisclosed Distributor #1
Oct 15, 2016

i was referring to the following sentence from the article on lux (minimum illumination)

Color vs B/W

Cameras that support integrated cut filters (aka D/N cameras) will often list 2 lux ratings, the first in color mode, the second in monochrome. This difference is due to increased performance in monochrome mode due to ambient IR light which the IR cut filter blocks in color mode .

here i could not understand what is meant by ambient IR light which is allowed in monochrome mode but not in color mode

U
Undisclosed #2
Oct 15, 2016
IPVMU Certified

Ambient IR light is really just the IR light that comes from the same source as the ambient visible light, like the sun or moon or light bulb.

As opposed to IR illuminators, external or integrated.

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Avatar
Donald Dubuque
May 09, 2018

The day and night camera delivers colour images during the day. As light diminishes below a certain level, it can automatically switch to night mode to make use of near infrared (IR) light to deliver high-quality, black and white images.

The IR Cut filter moves as light declines.

Image result for ir cut filter

Avatar
xiaoxiao zhu
May 12, 2018
IPVMU Certified

the imager can receive the visible light and infrared light. the IR cut filter will block the IR light when set to day mode.

Only when set to black/white mode, the whole lights will project onto the imager. but if it is in color image, the whole image will shift to red in the day time or the image will burst lots of noise in the night time as the visible light is almost gone. so the camera(ISP) will drop the color element(UV) and keep the luminance element(Y), just as the black/white mode.

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