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Here's how to make a perfectly round pinhole for least diffraction. You need a copper coin, an old steel acoustic gramophone needle, a cork, a fine sharpening stone, and a hammer. Cut the cork down to get a slice smaller than the length of the needle. Push the needle straight through the cork with a pair of pliers until the tip has only just perforated through. Pull it back a tiny tad. Place the cork on the coin needle point down. Give it a good wallop with the hammer. Repeat until a dimple appears on the other side of the coin. Remove needle from coin and use the sharpening stone to smooth down the dimple until a hole appears. Keep going, if necessary with some more needle hammering, until you have the diameter you want.
By the way, not only can you use extension tubes to increase the focal length, you can also shift the hole about sideways or up and down to get a lens shift effect, e.g. to correct verticals. You don't need tilt because it's all equally slightly out of focus
But a pinhole has a huge image circle and absolutely perfect linear geometry, so you can shift as much as you like.
By the way, not only can you use extension tubes to increase the focal length, you can also shift the hole about sideways or up and down to get a lens shift effect, e.g. to correct verticals. You don't need tilt because it's all equally slightly out of focus
But a pinhole has a huge image circle and absolutely perfect linear geometry, so you can shift as much as you like.
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WPPD 2015_Forthill Park Bandstand
