Pinhole and Resolution

Discussion in 'Pinhole Photography' started by ced, Oct 11, 2011.

  1. ced

    ced Member

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    Just wondering if anyone at this forum has any experience with measuring resolution on film/paper with a pinhole system?
    What is the highest attainable resolution with medium iso film for example?
    What about DOF any interesting observations?
    My apologies if this has previously been covered here.
     
  2. Jim Noel

    Jim Noel Member

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    Resolution is dependent on the crispness of the edge of the pinhole and the size relationship between the pinhole and the distance to the film.
    DOF is essentially from a few inches in front of the camera to infinity.
    I am quite sure this has been covered in far more detail elsewhere on this and other forums.
     
  3. Jim Jones

    Jim Jones Subscriber

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    Maximum pinhole resolution is more a function of pinhole size than format size. Therefore, wide angle pinholes for a given size can yield sharper images in the center of a photo than can longer pinholes. As I recall, the maximum line pair resolution of a pinhole of optimum size is slightly better than the pinhole diameter. This is counterintuitive, but diffraction limited optics don't behave according to simple logic. Nor do pinhole photographers!
     
  4. ced

    ced Member

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    Pinhole Resolution

    Jim thanks for this info. My observation but not fully confirmed is that on a 77mm f.length with a 0.37 p.hole size the best I could get was 6+ lp/mm at a distance of about 2m and in front and behind that the dof was very shallow with 3-4m out of focus making me think that the hole should still be smaller. Anyone else have some clear observations regarding this post are welcome.
    The newer 3 images at this link without the vignette are with 0.37 and the older 2 with vignette are with 0.42 surprising such a small reduction making such a big difference.
    http://www.flickr.com/photos/67202854@N05/
     
  5. Jim Jones

    Jim Jones Subscriber

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    I sometimes use Pinhole Designer (a free download) with a user constant of 1.5 for determining pinhole diameter for maximum on-axis resolution. My tests confirm that there is a rather sharp increase in resolution at the point where the diffraction and geometric resolution curves intersect. A slightly larger pinhole improves off-axis resolution with a loss of on-axis resolution. This may be desirable in some pinhole photography. The below charts graphically show the effect of increasing pinhole diameter. I donated the improvised camera to Eric Renner at Pinhole Resource many years ago, and don't intend to refine the off-axis test. It would be much easier to refine the on-axis tests with today's digital cameras. Maybe someday . . .
     

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  6. ced

    ced Member

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    Jim thanks, so it looks like the best one could get res. wise was about 5.5+ lp/mm correct? Which is about as close to what I observed, wonder if it can get much better as some users on this site and others show images that look as if they achieve higher resolution in their work.
     
  7. Jim Jones

    Jim Jones Subscriber

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    The highest resolution in my example above was indeed about 5.5 lp/mm on-axis with the 3.5 inch focal length. Changing the focal length changes the optimum pinhole diameter and thus changes the resolution. A contact print from a short focal length pinhole camera can appear quite sharp at normal viewing distances, but we tend to look at such small images at a closer distance. An image from a long focal length pinhole can look quite sharp if viewed from the distance which provides correct perspective. One way to predict this is to look at the actual backlit pinhole at a distance equal to the image viewing distance. If the pinhole appears to be a disk, the image probably won't appear to be sharp. The longest pinhole focal length I've used was about 24 feet for a solar eclipse. The negatives were dismally unsharp at arm's length, but sharp enough at a viewing distance of many feet.

    Sharpness can be clinically measured with resolution charts, but other subject matter imposes other standards of sharpness. A subject that is more shape and shadow than detail may not require nearly the resolution that a subject with much fine detail does. Image size and personal preferences are even more important in determining the required sharpness.
     
  8. ced

    ced Member

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    Agfa Clack with f245 0.37mm

    Thanks Jim. Here is a sample of a Pinhole image I find on the neg needs higher resolution but after putting it through digital mechanics the details are not bad but the grain gets amplified too.
    As in the true tradition of experimental photography an image of our street from the attic.
    At this link you pinholers are invited to download any one of these charts and run a test with your system sticking to the convention of 25 or 50 times the focal length of your pinhole lens and let us get some interesting input to those that may find it interesting. Tripod and stability through the exposure is vital! Enjoy.
    http://picasaweb.google.com/110822971980574262127/RandomImages?gsessionid=PFNPTRWkt5IlGtmohk4WJw
     

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    Last edited by a moderator: Oct 18, 2011
  9. X. Phot.

    X. Phot. Guest

    Is there a lens in this camera?
     
  10. ced

    ced Member

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    No but there is a focal length that needs to be considered.
     
  11. X. Phot.

    X. Phot. Guest

    Just curious. I've experimented with .5mm pinholes on 4x5 and 8x10 cameras (FL=170mm ~ 300mm), but never achieved what appears as barrel distortion in your last image. It must be the short FL.
     
  12. ced

    ced Member

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  13. keithwms

    keithwms Member

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    If you look around, I think you will find a thread in which Ralph Lambrecht gave some very helpful comments. Basically, there is more than one way to define resolution.

    Ah yes, here it is:

    http://www.apug.org/forums/forum62/66078-quick-question-about-pinhole-size.html
     
  14. ced

    ced Member

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    keithwms Thanks for pointing this out to me and very informative it is too.
     
  15. ced

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  16. RalphLambrecht

    RalphLambrecht Subscriber

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    hreis my take on this:
     
  17. RalphLambrecht

    RalphLambrecht Subscriber

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    a pinhole is an ideal only(diffraction-limited) lenscalculate the diffraction limit to get the pinhole resolution
     

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  18. Jim Jones

    Jim Jones Subscriber

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    I googled for a quality download of the USAF 1951 reslution test chart, but only found small or jpg files. This gif chart, small enough to post here, can be replicated to assemble a large chart for comparative testing of pinhole images. Print it without resizing to prevent introducing artifacts. The finest bars will not print perfectly due to dot spread. Actual line pairs per mm can be calculated. This was not included, as it would restrict the versatility of the chart. Feel free to post or publish it elsewhere. This is the information age, and knowledge should be as free as practical.
     

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  19. ced

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  20. RalphLambrecht

    RalphLambrecht Subscriber

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    feel free:http://www.darkroomagic.com/DarkroomMagic/Camera_files/USAF_1951 TestPattern.pdf
     
  21. Jim Jones

    Jim Jones Subscriber

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    Thank you, Ralph. That's what I was looking for.