Colour planes still existing after filtering

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    Colour Planes
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Discussion Overview

The discussion revolves around the phenomenon of blue and green color planes appearing in a photograph taken with a red bandpass filter. Participants explore the implications of using such a filter on color detection in digital imaging, focusing on the behavior of color-sensitive detectors and the characteristics of the filter used.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions how blue and green color planes can exist in a photo taken with a red bandpass filter, which is supposed to allow only red light through.
  • Another participant clarifies that filters and color-sensitive detectors are not perfect, suggesting that non-zero green and blue values can still appear in a digital image even with a red filter.
  • A further response indicates that the light passing through the red filter can still be detected by green and blue sensor pixels due to the broad nature of the Bayer filters, asking for specifications on the red filter used.
  • Another participant agrees with the previous points, noting that the spectral response curve of the blue and green sensors overlaps with the red part of the visible spectrum, allowing them to register a response.

Areas of Agreement / Disagreement

Participants generally agree on the idea that the spectral response of sensors allows for detection of colors outside the intended filter range, but the initial question about the presence of blue and green planes remains a point of exploration without a definitive resolution.

Contextual Notes

The discussion does not provide specific details on the characteristics of the red bandpass filter or the specifications of the sensors involved, which may influence the observations made.

vipis
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Hey. I am wondering how can blue and green colour planes exist in a photo, when I am using red bandpass filter while taking photos? Red bandpass filter let's only red light through. But when i analyze the photo, green and blue planes are still there. How can it be?

Thanks in advance
 
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What do you mean with "still there"?
Filters and color-sensitive detectors are not perfect (and they would not work as intended if they would be perfect) - even with a filter, you'll get non-zero green and blue values in a digital image.
 
vipis said:
Hey. I am wondering how can blue and green colour planes exist in a photo, when I am using red bandpass filter while taking photos? Red bandpass filter let's only red light through. But when i analyze the photo, green and blue planes are still there. How can it be?

Thanks in advance

If I understand your question, its because the light passing through the filter can still be (barely) detected by the green and blue sensor pixels- the Beyer filters are fairly broad, do you have any specs on your red filter?
 
I agree with Andy - the blue and green sensors will still register a response when exposed to red light because the spectral response curve partially overlaps the red part of the visible spectrum.

Claude.
 

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