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Theoretical Black and White Filter

  1. Oct 28, 2005 #1
    (hopefully I posted this in the right place)

    I am currently exploring the idea of creating a filter, with photographic application, that would allow for black and white images to be created without the use of black and white film.

    I am basically wondering if this is in fact a possibility, using a combination of colored filters (possibly red, green, and blue?) to make a single one. If it is in fact possible, and attainable, it would have numerous applications, from eye glasses to viewfinding filters for cameras.

    If anyone can steer me in the right direction, I would appreciate it. I only have one year of physics (adv. high school physics) under my belt, so I'm not exactly "in touch" with some of the terminology.

    Any help here would be sincerely appreciated!!
  2. jcsd
  3. Oct 28, 2005 #2

    Andrew Mason

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    White light has the complete spectrum (all colours). So you won't be able to get 'white' light by using filters. To get black and white images on colour film, take pictures of black and white subjects.

  4. Oct 29, 2005 #3


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    Your best approach, although it won't work for the sunglasses, is to use black and white film. Otherwise, Photoshop a coloured picture to greyscale.
  5. Oct 30, 2005 #4

    Andrew Mason

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    A colour blind person sees everything in black and white because his/her visual system distinguishes light intensity but does not distinguish between different wavelengths. So what you have to interpose between the object and the viewer is some apparatus that preserves variations in light intensity but does not distinguish between different wavelengths of light.

    If you want to create a 'live' image in b&w, you cannot do it directly with the original light using filters for the reason I gave above. You could, however, have a "red & black" image by filtering all but one particular colour of light. But this would mean that objects that reflect no red would look black and the objects that reflect red would appear in some intensity of red.

    To create a live black and white image for a non-colour blind person you would have to interpose a screen that responds to light of any colour by transmitting only white light whose intensity is proportional to the intensity of the incident light.

  6. Oct 30, 2005 #5
    Just a correction: true (black and white) colorblindness is rare, accounting for less than 1% of all colorblind people. The most common is red-green, followed by blue-yellow, then mono color (wherein one can only see one color), true colorblindness, and then progressive colorblindness (where one loses the ability to see color with age).
  7. Oct 30, 2005 #6
    A colour filter works by allowing certain colours through but not others. White light is a mixture of all colours and shades of grey are just due to variations in the intensity of the light.

    What you seem to be after is a filter that redistributes the intensity of the incomming light so that it is equally distributed amongst all the visible colours ( and is thus perceived as a shadw of white/grey ). This cannot be achieved through the use of separate colour filters since they only dimnish the intensity of some colours by a fixed proportion.
  8. Oct 31, 2005 #7
    Ok, I appreciate the feedback.

    Yes, I know that I can create a grayscale image using black and white film (i'm a B&W photographer), but yea, what i was getting at was creating a live image in black and white.

    So I'm getting that I likely cannot use colored filters to achieve this. But is there any way to do this without electronics or things of the like?

    The point of this is I want to make a filter that I could put over the viewfinder of SLR cameras (which do not have grayscale options) in order to create a preview, so to speak, of what the image would look like on black and white film (photographs in black and white can have worth when the same image in color is of no artistic worth, and this would allow to have a preview in order to see the worthy images without just guessing).

    So yea, is there any other conceivable way to do this? The project is not only for the result, but also for the process (as it is for a scientific research class, and I need a replacement project for my original engineering project).

    Thanks again!
  9. Oct 31, 2005 #8


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    The only other approach that comes to mind (although it does involve electronics), would be to retrofit a digital SLR viewfinder to your film camera and alter the circuitry to produce only greyscale outputs.
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