1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
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 to color

  1. Jan 10, 2010 #1
    isn't that different intensity of black and white in an old B&W photo correspond to a particular color range of the source.
    Which can then be converted into its original color?
     
  2. jcsd
  3. Jan 10, 2010 #2

    russ_watters

    User Avatar

    Staff: Mentor

    No, different colors do no conform to different intensities - play with a color photo and a photo editor and this will become clear to you.
     
  4. Jan 10, 2010 #3
    My dad, who grew up watching black and white films, claims he can tell the difference between colors in a black and white movie.

    Whether or not I believe him is a different thing.

    Also I kind of like the contrast of black and white. I think it makes things crisper than a lot of color movies.
     
  5. Jan 10, 2010 #4

    russ_watters

    User Avatar

    Staff: Mentor

    You sure that isn't just for objects he already knows the color of?
     
  6. Jan 10, 2010 #5
    Edwin Land, inventor of the Polaroid camera, would sometimes demonstrate the recreation of an (apparent) color image from two black-and-white slide transparencies using two projectors. Each projector alone projected a B&W image, but both together projected a color image. Here is a website discussing his technique.
    http://people.msoe.edu/~taylor/eisl/land.htm [Broken]
    I saw Edwin Land demonstrate this in the 1960's, and was totally surprised by the result.
    Bob S
     
    Last edited by a moderator: May 4, 2017
  7. Jan 11, 2010 #6
    when a color photo is converted into B&W, could that B&W photo be similar to the same souce but with some color changes and converted back into B&W
    OR
    does any intensity of Black or White correspond to more than one color
     
    Last edited: Jan 11, 2010
  8. Jan 11, 2010 #7
    Part of it is the shade of gray, the other part is his knowledge that a banana is yellow, and not pink.

    As for colors of unrecognized objects, I don't think so...
     
  9. Jan 11, 2010 #8

    russ_watters

    User Avatar

    Staff: Mentor

    Interesting experiment, though your description is somewhat inaccurate. One of the black and white slides was shot with a red filter, then projected with a red filter. So it is truly a red image through and through. Digital cameras work the same way, by using alternating colored filters on a monocrhome CCD.

    He didn't prove you can see color in a black and white image, he proved you can see all 3 colors in a red and white image. I suspect, though, that a lot of the reason this works is that there are similar proportions of blue and green in that image. I'll check into it with Photoshop when I get home tonight...
     
    Last edited by a moderator: May 4, 2017
  10. Jan 11, 2010 #9

    russ_watters

    User Avatar

    Staff: Mentor

    As I said above, any color can have any intensity. It would help a lot if, as I said above, you play with a photo editor to demonstrate for yourself, but here is a brief description of how a color image is represented digitally:

    Each of the three colors is assigned a brightness level from 0-255 and the three are then combined in each pixel to generate a color image. So you can have a pixel with any combination of brightness levels for each color, giving 256*256*256=1.67 million different colors.
     
    Last edited: Jan 11, 2010
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook