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I'm interested in trying out a bodycap style pinhole on my DSLR (a Nikon D3300 in my case).

Can I combine this with a macro extension tube to adjust the focal length?

Calculators such as Mr Pinhole seem to indicate that this would change the focal length and the viewing angle in the way I want, and reduce the amount of light reaching the sensor.

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Yes, you can.

But keep in mind that the optimal performance of a given pinhole is related to focal length used. More on the theme can be found here: How to calculate the optimal pinhole size?.

Using a macro tube extender will give you suboptimal results - the longer focal length of the "camera" would ask for a bigger pinhole than your bodycap.

On second thought: a small pinhole on a long tube will increase your exposure time considerably; possibly into area where noise caused by sensor heatup becomes an issue. This might be a bigger problem than diffraction.

But it will work.

  • True. However, if one were to create an ideal pinhole camera diameter for, say ƒ = 70mm, and using tubes allow ƒ to vary from 50mm to 100mm, then the deviation from optimal pinhole diameter will be less than the range of values for "optimal" diameter based on the constants given at the question you link to. That is, if C is chosen for around 1.71 and d is designed for ƒ=70mm, then when the tubes are at ƒ=50, the pinhole will perform the same as one if C=1.5. Similarly, when the tubes set ƒ=100mm, the pinhole will perform the same as one designed for C=2. – scottbb May 19 '17 at 23:31
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    Having tried homemade pinhole photography I know it will tolerate substantial departure from the ideal. Especially when using film (negative size matters; you do not enlarge as buch). But I felt the substantial work on the subject deserved pointing out :) – Jindra Lacko May 20 '17 at 8:00
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Can I combine this with a macro extension tube to adjust the focal length?

Yes, you can.

You can make some extension tubes with cardboard too to make some preliminary tests.

P.D. Just make sure you are buying the correct extension tubes. I am assuming you have a Nikon camera, as the link you provided is for Nikon.

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Making a pinhole camera with your camera body is easy. Just procure a set of tubes. Mount one and cover the other end with aluminum foil. Fix the aluminum foil in place using masking tape. Punch a hole in the center of the aluminum foil cover with a sewing needle. You can experiment with different size holes and different tube lengths. You can mount, painted flat black, cardboard tubes to adjust pinhole distance. For your camera, a pinhole distance to sensor of 30mm, should be your fist experiment. Next elongate the distance. Each time you double the distance, the light level at the sensor decreases 4X. Conversely, halving the distance yields a 4X brighter image. Aluminum foil and sewing needles makes for nice clean holes. You can experiment with different hole sizes.

You can convert your camera to a pinhole camera without buying tubes or lens cap. You Jerry-Rig a lens cap to fit over your existing lens. This is accomplished using aluminum foil and masking tape. Place a piece of foil over your lens and tape it in place. A neat way to do this is to cut a circle out of aluminum foil, just big enough to completely cover a UV filter. Puncture it in the center with a sewing needle. Use double stick cellophane tape to hold it in place. An alternate method; buy a sacrificial lens cover. Cut a ¼ inch hole in its center. Paste aluminum foil over this larger hole. Pierce this foil with a sewing needle.

This works because the center of the camera lens has little figure (its shape at this point is practically flat glass). A pinhole overlay acts as if the lens and its aperture (Iris) do not exist. Thus the pinhole acts as a pinhole.

Have fun.

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