BRAIN TEASER Thursday Poll

Discussion in 'US Coins Forum' started by Insider, Apr 8, 2022.

?

Where should the light be placed to best see the hairline scratch?

Poll closed Apr 10, 2022.
  1. 12 o'clock

    4.3%
  2. 3 o'clock

    19.6%
  3. 6 o'clock

    0 vote(s)
    0.0%
  4. 9 o'clock

    50.0%
  5. Directly overhead

    26.1%
  1. charley

    charley Well-Known Member

    That was good.

    The strange thing is, I don't remember giving him a Club Membership Card.
     
    Cheech9712 and Dynoking like this.
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  3. Mr.Q

    Mr.Q Well-Known Member

    For a know-it-all you sure don't know how to say Next Thursday, duh. I will wait and vote next Wednesday at 11:59.59 PM. Just a little fun, good luck.
     
  4. Insider

    Insider Talent on loan from...

    Good humor is great but if you didn't take the time to think about this question...

    Want to think a minute and take a guess in public? A or B?
     
    Mr.Q likes this.
  5. capthank

    capthank Well-Known Member

    I always thought natural sun light was preferred to examine a coin.
     
    UncleScroge likes this.
  6. Insider

    Insider Talent on loan from...

    capthank, posted: "I always thought natural sun light was preferred to examine a coin."

    OK, where did you hear or read that?


    OK, no replies so 1/3 of folks voted 3 o'clock and 2/3 of the votes were for
    9 o'clock. Anyone wish to tell us why 9 o'clock is the best answer and why?
     
  7. capthank

    capthank Well-Known Member

    I believe at our coin club.
     
  8. ToughCOINS

    ToughCOINS Dealer Member Moderator


    Lighting in the top photo appears to be from the coin's 8:00 clock position.

    In the lower photo, the lighting seems to originate at about the coin's 4:00 position.

    Surface area perpendicular to the light source determines how concentrated and bright the reflected light is.

    1. Light directed along the length of the scratch will reflect in the direction of the scratch. One might expect the light reflected by the full length of the scratch to be very bright, but it will be diffuse because of the varying angle of incidence (think varying focal distance and / or depth of field for a lens) along the length of the scratch.

    2. Lighting from 6:00 or 12:00 would reflect out the far end of the scratch, and not perpendicular to it, as would lighting from 3:00 or 9:00.

    3. The scratch is not straight. Curved as it is, I'd expect the reflected light from 3:00 to concentrate more, as if reflected by a parabolic mirror, while light directed at the scratch from 9:00 should disperse somewhat, and be less bright.
     
    Last edited: Apr 8, 2022
  9. Dynoking

    Dynoking Well-Known Member

    I’m getting ready to go out to dinner. I don’t have time right now to defend my answer. (9:00). But I can say this. My summary of this very educational thread is its important to angle the coin under the light left to right, top to bottom then rotate the coin 90 degrees and again above it top to bottom, left to right. Bravo Mr. I!
     
    Cheech9712 likes this.
  10. Dynoking

    Dynoking Well-Known Member

    PS.
    A mime?! I would have paid money to see that!
     
  11. Insider

    Insider Talent on loan from...

  12. Insider

    Insider Talent on loan from...

    ToughCOINS, posted:

    Surface area perpendicular to the light source determines how concentrated and bright the reflected light is.
    So I guess you voted for 3 o'clock?

    1. Light directed along the length of the scratch will reflect in the direction of the scratch. One might expect the light reflected by the full length of the scratch to be very bright, but it will be diffuse because of the varying angle of incidence (think varying focal distance and / or depth of field for a lens) along the length of the scratch.

    On the right track. Members my wish to take a circulated brown cent and put a straight, light, scratch on it and do an experiment to see if this is true.

    2. Lighting from 6:00 or 12:00 would reflect out the far end of the scratch, and not perpendicular to it, as would lighting from 3:00 or 9:00.

    On the right track.

    3. The scratch is not straight. Curved as it is, I'd expect the reflected light from 3:00 to concentrate more, as if reflected by a parabolic mirror, while light directed at the scratch from 9:00 should disperse somewhat, and be less bright."

    This is out-of-the-box thinking that I never considered. It would make a nice project for an optical lab to confirm this.

     
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  13. ldhair

    ldhair Clean Supporter

    To make a scratch show, you bring the lighting in perpendicular to the scratch.
     
    Insider likes this.
  14. ldhair

    ldhair Clean Supporter

    To hide scratches and hairlines you bring the light in parallel and reduce the contrast. It's easy to hide problems with images.
     
    Insider likes this.
  15. -jeffB

    -jeffB Greshams LEO Supporter

    I was thinking to ask what difference there would be between 3:00 and 9:00. The important thing is to have the light direction perpendicular to the scratch, as @ldhair said.

    I can imagine that the scratch will look different depending on whether the light comes from the left or the right. The profile under the scratch is slightly angled toward the left, which makes me think light coming from the right (3:00) would throw the feature into higher relief.

    As far as convex/concave and focusing the light: I don't think that's a factor at all. The reflection that matters is from the direction of the light, outward from the coin's surface, toward the eye or camera. Whether the scratch curves left or right shouldn't make any difference.
     
  16. Mr.Q

    Mr.Q Well-Known Member

    I voted probably wrong but I voted.
     
    Insider likes this.
  17. Scott J

    Scott J Well-Known Member

    9:00 to create contrast, the high part of the scratch will cast a shadow.
     
    spirityoda likes this.
  18. ldhair

    ldhair Clean Supporter

    You can also play with the lighting to make something show more detail.
    Raise or lower the lights and angle the light is hitting the surface of the coin.
    It's fun to play with.
     
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  19. justafarmer

    justafarmer Senior Member

    You place the light at the same angle and from the same direction the force from the object that created the scratch on the coin initiated from. It doesn't matter whether you adjust the direction of the light relative to the coin or adjust the position of the coin relative to the light. Of course this assumes the direction of the light source and the direction one is looking is the same.
     
  20. green18

    green18 Unknown member Sweet on Commemorative Coins Supporter

    I voted 3:00 but I'm beginning to think the light source is 9:00 due to the 'hot spot' on Libertys' chin........
     
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  21. charley

    charley Well-Known Member

    The problem I have, is the candles keep flickering with the slightest air movement, whenever I look at the coin. I tried to stop breathing, but it didn't help. I blacked out.
     
    Cheech9712 likes this.
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