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Making the hole for a pinhole camera

In search of the perfect pin hole


The front panel of a 5 X 7 box pinhole camera, showing the opening that is blocked by the pinhole plate. The pinhole drilled in the center of the plate is so tiny, it is difficult to see.
The front panel of a 5 X 7 box pinhole camera, showing the opening that is blocked by the pinhole plate. The pinhole drilled in the center of the plate is so tiny, it is difficult to see.

Three steps must be followed in making a perfect pinhole:

  • Determine the optimal hole size for the film-to-pinhole distance;
  • Create a perfectly round and smooth hole; and
  • Ascertain whether your pinhole is the "right" size by measuring it.
  • There are many published formulas for determining optimal pinhole size, some of which rely on complex mathematical calculations involving the wave theory of light. We're not going there! Instead, we'll use a formula from Eric Renner's definitive book: Pinhole Photography, Rediscovering a Historic Technique.


    Formula for determining optimal pin hole size, where the optimal aperture, in thousandths of an inch, is A, and the film-to-pinhole distance (or focal length) in inches is F,

    A= the square root of F x 55.
    For example, if the pinhole-to-film distance is 4 inches, 4 x 55 = 220. The square root of 220 is 14.8 thousandths of an inch. Voila! The perfect size.

    Another example: Say you want to make a camera that uses 35mm film and a focal length of 5/8 inch for an extra wide angle of view.

  • First, convert 5/8 inch to a decimal, which is 0.625 inches.
  • 0.625 x 55 = 34.38, the square root of which is 5.86.
  • Round 5.86 off to the nearest 1/1000, which is 6 thousandths of an inch - the optimal aperture for the 5/8 inch focal length.


  • That's pretty tiny, barely large enough to see with the naked eye. And that is the challenge - to make a perfectly round and smooth pinhole 6 thousandths of an inch in diameter.

    It's worthwhile taking the time to properly drill the optimal pinhole size. It may seem like a chore as you do it, but you will be rewarded with years of superb pinhole camera photographs, and the exacting care you took will be a dim memory.
    It's worthwhile taking the time to properly drill the optimal pinhole size. It may seem like a chore as you do it, but you will be rewarded with years of superb pinhole camera photographs, and the exacting care you took will be a dim memory.

    The pinhole must be perfectly round and smooth, and of precisely the right diameter for the focal length.
    The pinhole must be perfectly round and smooth, and of precisely the right diameter for the focal length.

    The secret to making such a small pinhole is to use a needle as a drill, not as a spear! Start with the smallest needle you can find (consult with your mother, which is a good habit in life).

  • Rough up a side of the shank, from the tip down about an eighth of an inch, with a piece of sandpaper or a sharpening stone. Use the finest sandpaper or stone you can find.
  • Now take a piece of brass shim stock, about an inch square, and tape it down on a piece of cardboard.
  • Place the needle between your right hand index finger and thumb and bring the needle lightly to rest, upright on the center of the shim stock.
  • Rest your left hand's index finger lightly on top of the needle and begin twisting the needle like a drill, back and forth.
  • Continue twisting this way for about a minute, then remove the needle, untape the shim stock and hold it up to the light for a look.

  • Can you see through the pinhole? You may need a magnifying glass to see such a small hole. Incidentally, the normal lens from a 35mm SLR camera or a dSLR, reversed, makes a great magnifying glass.
  • If you can't see through, resume drilling (you may need that magnifying glass to get the needle back into the hole).
  • If you can see light through the pinhole, take the square of shim stock and place it on a sharpening stone or piece of emery sandpaper (the finest grade you can find).
  • With your thumb pressing hard against the shim stock, right over the pinhole, commence rubbing the shim stock against the stone in a circular motion. This will remove any burrs and polish the edges of the pinhole.
  • Flip the shim stock over and repeat the process.
  • Now rinse the pinhole with water and hold it up to the light for another look.
  • Is the pinhole perfectly round, smooth and free of any debris?
  • If not, re-insert the needle, clean it out, re-rinse and look again, closely at both side of the pinhole with your magnifying glass.
  • Hold the drilled hole up to the light to learn whether you can see through your new pinhole. If not, keep at it; you haven't drilled through yet, or the hole is too small. Take your time, and check several times. Slow and steady makes a perfect pinhole.
    Hold the drilled hole up to the light to learn whether you can see through your new pinhole. If not, keep at it; you haven't drilled through yet, or the hole is too small. Take your time, and check several times. Slow and steady makes a perfect pinhole.

    The finished pinhole plate can be attached inside the camera using black vinyl tape to mask the edges so that no light can enter through the sides.
    The finished pinhole plate can be attached inside the camera using black vinyl tape to mask the edges so that no light can enter through the sides.

    But is the hole the optimal size? To answer that question, you will need access to a regular photographic enlarger and a thin, transparent ruler. (You can also use a slide projector instead of an enlarger. The procedure and principle are the same.)

  • Place the ruler in the negative carrier of the enlarger.
  • Turn on the enlarger and raise the head until one inch of the scale on the ruler is projected so that it measures ten inches on the baseboard.
  • Remove the ruler from the negative carrier and replace it with your pinholed shim stock, leaving the enlarger head at the same height.
  • Now your pinhole can be seen on the baseboard, enlarged to precisely ten times its size.
  • Measure it with the finest scale ruler you have and divide the result by ten.
  • Finally, convert this fraction to a decimal.
  • Is the pinhole too small? You can always drill it out to be a bit bigger.
  • If it is too big, unfortunately you will have to start over.

  • If you have trouble seeing whether your pinhole is accurately drilled, ask a keen-eyed consultant to check it out.
    If you have trouble seeing whether your pinhole is accurately drilled, ask a keen-eyed consultant to check it out.