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Insights Lenses and Pinholes: What Does "In Focus" Mean? - Comments

  1. Mar 29, 2017 #1

    stevendaryl

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  2. jcsd
  3. Mar 30, 2017 #2
    Great addition to our FAQs!
     
  4. Apr 2, 2017 #3

    kith

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    For an introductory article, I think it would be good to include a small paragraph why we need the pinhole in the first place.
     
  5. Apr 3, 2017 #4

    Drakkith

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    I like what you've done with figure 2. It shows that if you take 2 different rays from the same point, then they essentially help form two separate images of the same object at slightly different locations which may overlap each other. Taken to the extreme, this means that without a lens, there are an "infinite" number of overlapping images that wind up being a blurry mess. The smaller the aperture, the tighter the grouping of the images and the less blurred the overall image is.
     
  6. Apr 12, 2017 #5

    sophiecentaur

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    "It seems like a superior way to do cameras, because there is no need for focusing."

    Reference https://www.physicsforums.com/insights/lenses-pinholes-focus-mean/

    As a matter of fact, extreme depth of focus is not always an advantage. Limiting the depth of the sharp field is an important aspect of many photos for artistic reasons and also for emphasising and isolating detail. Binoculars can often allow you to see a bird behind a bush because the bird can be in sharp focus and the bush can be a blur. Also, of course, diffraction rears its ugly head with small apertures. If you want to image two closely adjacent stars, you will be needing a telescope objective of many (even hundreds of) cm diameter. It's horses for courses, as ever.
     
  7. Apr 12, 2017 #6

    Drakkith

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    I'm... not sure I know what that means, lol.
     
  8. Apr 12, 2017 #7

    sophiecentaur

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  9. Jun 9, 2017 #8
    After reading this , I understood what is exactly meant by " in focus".

    Thank you, thanks a lot for posting this insight post.
     
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