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I understand Bayer filter is a type of color filter array used in digital cameras to create a color image. What happen to the digital image if I capture it without using any color filter arrays?

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    If you "understand" that the purpose of the Bayer filter array is "to create a color image", what should the consequence be if it is absent? Or do you have something else in mind when you ask "what happen[s]"?
    – xiota
    Jun 20 at 5:39
  • @xiota Will it show Black and White?
    – Josh Alex
    Jun 20 at 5:47
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    @JoshAlex What does the processing algorithm think? Does it assume the CFA is still there? Or has it been told a CFA is not there?
    – Michael C
    Jun 20 at 8:07

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Yes, the image you get will be black and white. "Generation" of colours in the image are based on Bayer (or Foveon or X-Trans) filter. The process is named demosaic.

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    Not unless the decoding software is aware there is no CFA. That is, if the CFQ is removed but the raw file is still processed by an application that operates under the assumption the CFA is in place, the result will not be B&W, but the colors will be bizarre and nowhere near what one would expect.
    – Michael C
    Jun 20 at 7:55
  • @MichaelC, that is true if we get in consideration many if's in the question.
    – Romeo Ninov
    Jun 20 at 8:05
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It all depends upon the set of instructions used to decode the information collected by the sensor. If you remove the CFA but don't tell the software used to process the raw data, you WON'T get a B&W image as expected, but you won't get a color image anything like you would expect, either.

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  • The image would probably also be overexposed, as the exposure controls of the camera would expose for a sensor with filters and without the filters much more light would reach the sensor.
    – slingeraap
    2 days ago
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    @slingeraap That assumes one is using an automated exposure mode. Also, due to the overlapping sensitivity needed to imitate human vision, the color filters are fairly weak and allow around half of all light that strikes the CFA to pass through, so at most it's only one stop.
    – Michael C
    yesterday
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In most cameras, a color filter array is necessary to reconstruct color from a single capture. Without the filter, the result is a representation of the intensity of light captured by the sensor, but the raw data still needs to be processed to produce a usable image. The typical result would be a monochrome image.

The sensor also has other filters, notably to block UV and IR. The photographer may also choose to use color filters for creative effect. Color can be reconstructed by combining multiple frames captured with color filters.

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  • You didn't mention what happen to the image.
    – Josh Alex
    Jun 20 at 6:25
  • "The typical result would be a monochrome image." But depends on how you process the raw. It's not necessarily "black and white".
    – xiota
    Jun 20 at 6:31
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This is not an abstract question. You can actually buy cameras which don't have a color filter. See the Leica Monochrom for instance (manufacturer's site). Monochrome camera's are used all the time for scientific imaging, especially when working with fluorescence. By eliminating the color filter, you effectively improve the spatial resolution.

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If there is no color filter array, then every pixel on the sensor has an equal (panchromatic) color response.

If the software processing the sensor data knows this, then the result is panchromatic black and white.

If the software processing the sensor data still thinks there is a color filter array (like if this was a radical mod to an existing color camera) then the result would be an almost-black-and-white image with color fringing in high-frequency high-contrast areas, as the demosaicing algorithm interprets the differences between neighboring pixels (which it thinks have different color responses) as color differences.

You don't actually have to remove the CFA from a sensor to see this: just look at what happens when a color digital camera without an optical low-pass filter shoots a high-detail black and white target:

color moire fringing on a black-and-white test pattern

(this is a 200% crop of a very small portion of the studio test image from DPReview's OM-System OM-1 review).

You'd probably also get a slight color cast (not true black-and-white) because the out-of-the-box white balance settings are tuned to the T-factors of the color array that isn't there, but that would be easily fixed with a filter in front of the lens, or pressing the Custom White Balance button while pointed at anything.

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