Building a Pinhole Camera

Discussion in 'Pinhole Photography' started by WGibsonPhotography, Jun 24, 2009.

  1. WGibsonPhotography

    WGibsonPhotography Member

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    After reading Cus's pinhole camera thread, I decided that I wanted to build a pinhole camera (or at least design one on paper and give up after the math required to design one kicked my butt). :smile:

    I printed out an article on Geocities that gave the pinhole diameter formulas, f/stop formula (which I already knew), and other calculations. This article gives aperture diameter formulas in inches and millimeters. I decided to use millimeters because I'm more familiar with the metric system. The formula for pinhole diameter in millimeters is.

    "Pinhole Diameter=0.0366(square root of focal length)"

    Since I'm not a fan of math, I decided to use a nice, even number. I stupidly picked 1mm as my diameter, not thinking of how big that would make the camera. I ended up with a camera 15.8 feet long :\

    If anyone is interested in how I (correctly ir incorrectly) came up with that, I'll type out my process.

    Pinhole Diameter=0.0366(square root of focal length) with a 1mm pinhole diameter

    1=0.0366(square root of x)

    1^2=(0.0366^2)(x)

    1=0.00133956x

    1/0.00133956=x

    x=746.5137806

    I rounded 746.5137806 to 746.5mm

    To get 15.8 feet, I multiplied 746.5 by 10 to get 74.65cm. I then divided 74.65 by 2.54 to get 29.38in.

    This is actually a lot more practical than the calculation I had before. It's amazing how one mistake can throw a measuremoent off that much :smile:
     
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  2. bdial

    bdial Subscriber

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    Your Metric to English conversion is off, to go from cm to inches you divide. 74.65 cm is 29.38 inches (74.65/2.54). Still pretty long but not so bad as 15 feet (4572 mm).

    If you have access to, or buy a machinist's caliper, you can just measure the needle, then using the formulas figure out what the FL would be. Cheap ones are around for 20 USD, or so.
     
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  3. Paul Cocklin

    Paul Cocklin Member

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    I'm afraid the math is incorrect. You shouldn't multiply your cm to get inches, you should divide. A quick look shows that 746mm is less than 1 meter, so it's got to be under 3 feet. Notwithstanding this, it would still be a big camera. :smile:
     
  4. Christopher Walrath

    Christopher Walrath Subscriber

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    Wirelessly posted (BlackBerry9000/4.6.0.167 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102 UP.Link/6.3.0.0.0)

    Mike your needle and multiply by 300 (edit) to get your focal length () and you should have a great aperture.
     
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  5. BetterSense

    BetterSense Member

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    I think you mean focal length.
     
  6. DWThomas

    DWThomas Subscriber

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    As long as the needle has a good sharp point, the dimple-and-sand method can produce a pinhole smaller than the needle diameter. You don't push the needle through, you just raise a bump and use fine sandpaper to remove enough material to expose a hole. (I use #600 wet-or-dry wet.) That process also gives the hole some approximation of a knife edge. Then you can work your way up to the desired diameter. The trick is being able to measure where you are. Purely by accident, I have a little 50x hand-held microscope with a direct measuring reticle built in, which works for me, but I know some folks are pretty successful using a [whisper] scanner [/whisper] to come up with a measurement.

    I would be inclined to pick the "focal" length and then work up the pinhole size. But that's partly because my efforts to date have involved making adapters to fit existing camera gear.

    DaveT
     
  7. WGibsonPhotography

    WGibsonPhotography Member

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    I actually thought that very same thing as I was driving around in my car just a while ago. Apparently I shouldnt be doing metric to english conversions early in the morning :smile:

    I'm suprised it was the conversion that I screwed up and not the actual focal length formula. A pinhole camera just under 30in is much more doable than a 15 footer. I wouldnt be able to fit something 15 feet in my car :smile:
     
  8. WGibsonPhotography

    WGibsonPhotography Member

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    I have one more question: Would balsa wood be an appropriate material to make a pinhole camera out of (painted, of course)? I think I can get sheets of it at a local crafts store.
     
  9. BetterSense

    BetterSense Member

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    Take a high-powered flashlight and hold it right up against the material, and hold it right next to your eye while sheilding it with your hand. If you can't see the light at all when you turn it off and on, it should be good. I doubt balsa wood will be light-tight enough.
     
  10. WGibsonPhotography

    WGibsonPhotography Member

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    that's a good idea. Balsa wood is pretty thin, and I doubt it'll be good enough unless I paint it. Even then, the paint might be good enough. I should be able to find something at Hobby Lobby that'll work, even if it isnt balsa wood :smile:
     
  11. DLM

    DLM Member

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    At some of the art supply stores, Ive seen some of the balsa in thicker sheets, so that may be an option. I think I might look for some to make one, or just use foamcore since it's easy to glue together and is really light.
     
  12. Rick A

    Rick A Subscriber

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    I too have been bitten by the pin-hole camera bug. This is a project for my 11 year old daughter and self. we are using a left over Christmas popcorn tin- 9.5in.diameter by 10.5in. tall. By my calculations, we can get a 5x7 negative using the bottom for the pin hole and the lid for the negative . this is dictated by the lid size. However, we can get an 8x10 panorama using the side forour set up.
    Rick
     
  13. jnanian

    jnanian Advertiser Advertiser

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    if you want to do it the easy way ...
    go to pinhole resource . com

    or look for pinholebilly on eBoo they make custom laser cut holes ...

    the easy rule of thumb for pinhole coverage is 3 or 3 1/2" x ( relative) focal length of lens will tell you coverage / image circle.

    have fun!
    john
     
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  15. bdial

    bdial Subscriber

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    Yes, I found the Pinholebilly method much easier. For 25 or so bucks you get a stack of them in different sizes.
    You do miss out on the cutting up pop cans, or going to the hardware store and asking for "shim stock" and getting blank stares part.
    And the figuring out how to just dimple the metal and sanding it just right part.

    But there is plenty fun to be had in building the rest of the camera or fitting one of the holes onto a suitable camera body.
     
  16. WGibsonPhotography

    WGibsonPhotography Member

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    Thanks for all the replies. The more I think about building a pinhole camera, the more I want to do it. Hopefully I'll have a rough sketch of my camera and the dimensions later tonight :smile:
     
  17. Darkroom317

    Darkroom317 Member

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    Any idea what size pinhole I would need for 6 x 9 120?
     
  18. WGibsonPhotography

    WGibsonPhotography Member

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    I used the pinhole calculator here http://www.mrpinhole.com/holesize.php to find what the image circle and the f/stop would be. Using the focal length of 746.5 that I came up with earlier, the calculator told me the image circle diameter would be 1433mm and the f/stop would be 648. What caught my eye was the pinhole size. According to my formula (which I'll post at the bottom), the pinhole diameter should be 1mm. According to the calculator, the pinhole diameter should be 1.15mm.

    The calculator must be using a different formula than me. What formula is the calculator using, and is that more accurate than mine?

    the formula I use is "pinhole diameter=0.0366(square root of the focal length)"



    I know I posted my formula on my first post. If someone knew the answer to my question, I didnt want that person to have to go to page one of the thread to find it :smile:




    Edit:

    I played around with the focal length on the calculator to find what focal length I sould use if I have a pinhole of 1mm. The calculator told me 565mm. I know that would be a freaking huge pinhole camera, and I really have no intention of building one this big. I'll just use a smaller pinhole and make a smaller camera. I'm just using the measurments I came up with earlier as an example
     
  19. BetterSense

    BetterSense Member

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    I might pay 25 dollars for an assortment of pinholes, but pinholebilly isn't selling any on the auction site right now.
     
  20. jnanian

    jnanian Advertiser Advertiser

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    the other nice thing about a laser-cut hole
    is the pinhole is exact and "relative to f16" so you can
    take a light meter reading and figure out the exposure ...

    i am sure if you go to a completed auction
    and ask a question of the seller
    you can find out when his next auction will be ..
    or you can ask him what his email address is
    and buy from him directly ...

    making the hole is kind of fun, but billy makes it painless ...
    i bought mine from him pre-ebay .. he has been making
    these a very long time, and he is a very nice guy.
     
  21. DWThomas

    DWThomas Subscriber

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    Methinks accuracy is a somewhat subjective term here.

    One of the formulas often referenced is:

    d = c * sqrt( f * l)

    Where d is the pinhole diameter
    c is a constant (that's where the trouble starts)
    f is the focal length
    and l is the wavelength of the light (more trouble)

    Folks seem to use 0.00055 for the light wavelength (which might be a green) but the spectral sensitivity of the film could come into play. Ortho film would likely produce sharper results if one optimized for the appropriate wavelength.

    The constant --- oooh --- I think Lord Rayleigh, an early tinkerer with these matters, came up with 1.9. But I've seen people using numbers as low as 1.5. Obviously this cauld bend the results quite a bit. In my quick perusal of the MrPinhole calculator, I didn't see an indication of what he used, although it may be lurking there somewhere. Pinhole Designer defaults to .00055 for the light wavelength and 1.9 for the constant, but gives a user the option to edit those values.

    Edit: The 0.0366 is simply bundling numbers, the product of the constant, c, and sqrt( wavelength) for metric values; 0.0073 for inches.

    When one considers the issues of fabrication, pinhole cutting, reciprocity failure and possible film flatness problems, it's probably not worth doing three decimal place calculations here. :D

    DaveT
     
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  22. DannL

    DannL Member

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    Using the calculator at http://www.mrpinhole.com/calcpinh.php I plugged in the numbers shown below. The numbers were very accurate for the camera that I was designing. I was using paper negatives. The most difficult task (massive quantities of time spent) was designing a "serious pinhole". Thin brass plate seems to be the best material from my own experience and from reading the earliest articles on the subject. The angle of view using those parameters appear close to a normal viewing angle in contact prints made from the 4x5 paper negatives.
     

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  23. WGibsonPhotography

    WGibsonPhotography Member

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    Well all of that makes sense. I actually did some research on the subject and found an article mentioning Rayleigh and some of the physics involved, including wavelengths of light and the constant and what the constant meant. I had an allergy headache from mowing grass, so none of it really made much sense. I printed it out, and I'll read it again tomorrow.

    Maybe I shouldnt research too much on this subject. Perhaps I should just take the recommendations of the pinhole calculators, not worry about all the physics, and just have fun. :smile:
     
  24. Rick A

    Rick A Subscriber

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    Whatever happened to the simple oatmeal box pin hole camera? I made one in college a hundred years ago, and there wasn't all this fuss over all this rediculous math. All we did was paint the thing black inside, cut out for the "lens" cut the stupid steel beer can and drill it and tape it on the box. All the fun is wasted and lost fretting over the math just to get it PERFECT. My daughter is thrilled to be just making something that will show results , and allows her to EXPERIMENT with all the variables. IMHO we all spend too much time overcomplicating our hobbies and our lives by trying to be the absolute authority on any given subject(self included). My daughter remindes me daily what a ninny I am for this, when all she is interested in is the "fun" aspect of photography.
    Rick
     
  25. WGibsonPhotography

    WGibsonPhotography Member

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    You got a point there. I might just make one as good as I can without all the math, and then experiment later.

    Trying to figure out all this "rediculous math" is pretty cool, I think (even though math isnt my strong point, and I'm probably spending more time figuring it out than a smart person :smile: )
     
  26. DannL

    DannL Member

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