Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

B&W Glass Filter

  1. Nov 7, 2006 #1
    Hi to all!

    I have a little question for you. Does a b&w glass filter exist?
    I now there are all kind of color glass filters, but I want to know if there are any possibilities to generate a b&w image without using your camera or your computer.
    I know about the monochromator device, but it acts on a single ray. I'm not sure if I could get an image using a monochromator.

    Any help would be appreciated!
     
  2. jcsd
  3. Nov 7, 2006 #2
  4. Nov 7, 2006 #3

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Not that I know of, no.

    - Warren
     
  5. Nov 7, 2006 #4

    Danger

    User Avatar
    Gold Member

    The problem that I can see here is that white light is composed of all wavelengths. As soon as you start filtering out colours, it can't exist.
     
  6. Nov 8, 2006 #5
    What if it is somehow possible to get equal value for R, G and B? I'm not sure whether this works in the real physical world, but I know that a color with a value RGB 50/50/50 (or simply said x/x/x) is a greyish color.
     
  7. Nov 8, 2006 #6

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Well, a "black-and-white filter" maps a color (R, G, B) to a colorless triple like (R+G+B, R+G+B, R+G+B). This filter involves adding frequencies together, which physical filters cannot do. All that a physical filter can do is remove frequencies from its input.

    - Warren
     
  8. Nov 8, 2006 #7

    Danger

    User Avatar
    Gold Member

    I just had me a thought here, but I don't know if it would work.
    Take one R filter, one G, and one B. Mount them side-by-side, then use lenses to correct for parallax and focus them all on one viewing area.
    Chroot...?
     
  9. Nov 8, 2006 #8
    Danger, I had a similar idea, too. But chroot said that a physical filter only removes frequencies from its input. I think that this will produce a totally white image. Am I right or....?
    I was actually imagining as if the picture passing thorugh a monochromator, it seperates the different colors, and then they're somehow equalized to the same value, thus producing a b&w image. Correct me if this doesn't make any sense :)
     
  10. Nov 8, 2006 #9

    Danger

    User Avatar
    Gold Member

    I'm going to wait for Chroot or someone else about this. I'm over my head.
     
  11. Nov 8, 2006 #10

    Mech_Engineer

    User Avatar
    Science Advisor
    Gold Member

    I think the 3-color filters method is how they capture images on spacecraft and the mars rovers... Combined they give you a full color picture.

    You can capture a black & white picture on B&W film, btw.
     
  12. Nov 8, 2006 #11
    Mech_Engineer, a b&w film works different. The film has some kind of grains on it, which are light-sensitive. As soon as the lighting strikes over them, they can't "reset" anymore. I want to be able to see through those filters or whatever it is, and see a b&w representation. I don't need a still image. Hope you understood me. Thanx for the tip, btw.
     
  13. Nov 8, 2006 #12
    Chroot, What do you think about Danger's preposition?
     
  14. Nov 8, 2006 #13

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Danger's idea would not work.

    Imagine that the image you want to pass through your filter has only the color red in it. Your desire a filter that produces a grayscaleB] output. In other words, dim red light would appear on the output screen as dim white light; bright red light would appear on the output screen as bright white light.

    Assume that you pass your red image through Danger's three-filter system. The red light would go through the red filter, but will be blocked by the green and blue filters next to it. The final image formed will be... red. Not white.

    - Warren
     
  15. Nov 9, 2006 #14

    Danger

    User Avatar
    Gold Member

    Warren, I think that I might not have expressed my intention properly, given your response. The filters that I proposed are beside each other, not in line. Lenses compensate for the parallax difference, so that each one 'sees' the same image despite their spatial orientation. You then have one red image, one green image, and one blue image all coinciding at the same viewing pane. It still might not work, but not for the reason that you cited.
     
  16. Nov 9, 2006 #15

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Danger,

    I understood your proposal perfectly well. You didn't understand my response.

    For example, the desired "black and white filter" would convert an image containing nothing but shades of red into shades of gray, based on their intensity. Your filter setup could not do this. If you pass red light through your side-by-side red, green, and blue filters, you will get a red image on the other end.

    - Warren
     
  17. Nov 9, 2006 #16
    Indeed, what it would need here is the opposite of a filter: a device that trasforms the energy of a specific frequency into the same energy equally distributed on the entire visible spectrum; instead of a "monochromator", a "multichromator"!
    Are there optical crystals which can have a similar property or, at least, which can broden the spectrum's range of a light source?
     
  18. Nov 9, 2006 #17
    So, you mean that you could simply need a B&W videocamera?
     
  19. Nov 9, 2006 #18

    Danger

    User Avatar
    Gold Member

    I'm going to have to bail out of this one, guys. It seems to be something that I know so little about that I can't even quite follow the explanations. I'll keep reading to learn more, though.
    Meanwhile, how about a night-vision device or a simple B&W TV camera?
     
  20. Nov 9, 2006 #19
    Chroot, you said that the filter should be able to add frequencies together. Is there any physical way to accomplish this? For example to seperate the image on 3 channels and then add their frequencies together?
     
  21. Nov 9, 2006 #20
    Danger: My initial plan was to create a mirror which will reflect a B&W image, instead of color. But I would be happy ig I could make a simple B&W image without using any electrical stuff.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?