Tuesday, February 5, 2019

A 6x9cm Variable Cuboid

I wasn’t going to make a 6x9cm Variable Cuboid. My relationship with the 6x9cm format has been rather lukewarm, maybe because my early experiences with it coincided with the development of the 35mm Populist. I was besotted with the pinholey image quality from the smaller negative, which has the same aspect ratio. The 6x9s seemed a little dull. Looking back on those pictures, they’re not bad and lately 6x6cm has gotten to be an obsession so maybe another try is warranted.

One other thing that discouraged me is with 6x9cm format there is the option of choosing a vertical or horizontal format. In order to have a rising front (another infatuation) in both orientations, there has to be a third pinhole and shutter. That's how it is with the Pinhole Lab Camera with tape shutters and with Reality So Subtle cameras with precision engineering and manufacture. It's been done with flaps that swivel away on a screw to uncover the opening. Except for tripod mounts, metal fastener technology isn't part of my repertoire. The flaps might catch on something and bend and they seem a little fussy to open and close for a quick exposure. My standard cardboard sliding shutters are too big to be close enough to operate for three holes without making the rising distance a little too far up for normal use on that third pinhole.

Not to mention it would need another identical pinhole drilled.

The thought crossed my mind that my normal shutter would work if it could just rotate 90 degrees. Making something that rotates isn't that different than something that slides back and forth. The result is the same double shutter from the Evil Cube Template, with the corners rounded off to make a circularized shape mounted on a turntable of a larger radius, inset in a base with a hole the same size, which is then held down by a cover with a slightly smaller radius opening.Wherever it moves it's greased with pencil graphite.

The two pinholes have to be offset from the center because the on‑axis pinhole has to be, well...on‑axis so it’s in the middle whichever way it’s rotated. The top sliding shutter gets a little wiggly when it’s opened because the channel is now shorter on the top but it’s OK if you’re half-way careful when opening it.

Putting some stops at the 90 degree positions would make it really quick and easy to get it square when you turned it from horizontal to vertical, but then it occurred to me that it could now rotate all way over for a falling front in case you were high in a building and wanted to keep the verticals parallel on the building across the street. Oh well, it’s pinhole, so taking a few seconds to line the shutter up with a mark isn’t out of the question.

Another random thought about the 6x9 format was that it was the same size piece of film as two 4.5x6cm frames. Hmmm. Side by side frames. That sounds a lot like stereo. There could just be two pinholes (well, four with rising pinholes, but oh well) on a front separated by 4.5cm, with a septum running down the middle of the inside.

On my older stereo cameras there are two single Populist shutters connected by a bar so they opened at the same time, but that wouldn’t work if you had a rising front pinhole.The new one has a double shutter, with two openings on the outside, with a wide slider that has a slot in it which uncovers the second hole when the shutter passes the first hole and hits it’s stop.

I made a 55mm stereo front. For view finding it has a line of black card stock to define the image plane and beaded pins in the front to mark the pinholes. Something with depth makes view finding easier for me than just drawing lines on the camera.

For the whole 6x9 format with the rotating shutter I made a 70mm front.

One problem with the 360 degree rotating shutter is now there are three places on each side where there might be a pinhole. I was sick of covering the shafts of those beaded pins with tape on the inside of the camera and repeatedly sticking my fingers. The rising pinhole is 15mm from the axis, so instead this front has pieces of card stock 30mm wide, with a notch in the middle to show me where the pinholes could be.

The 55mm stereo has .3mm hand-drilled pinholes and .34mm for the 70mm. It was surprisingly easy. It's always been hard for me to hold the needle with my big fingers to prevent it from bending while drilling down and to keep it vertical. In another moment of what seemed to me as brilliance, I had the thought that the needle could be held straight by holding it stuck through a piece of foam core. It works great.

First up was the 55mm stereo front and the back loaded with Arista.edu 100.

The following stereo pairs are set up for crossed eyes, which is really easy because the negatives can be scanned together just as they come out of the camera, left image on the right and right on left. If you don't think you can do crosseyed stereo viewing, check out this exercise. You probably can learn to do it right away.

Here's an Amarylis in front of a mirror portrayed with the on‑axis set of pinholes. Try to line up the flowers.

Well, this is interesting. You'll note the left image is wider than the right.

I have to confess that I just made up the divider as I put it together. The result is a kluge of several odd pieces of foam core bracing the divider and making sure it was square. These parts don't extend all the way to the edge because they might block some of the image. Also, the front and back of the camera meet 10mm in front of the image plane and this septum needs to go all the way back to the film. The result is that it's a little flexible. When I put the front on the back it bent the divider one way by about 5mm. It went together easily and nothing seemed wrong until I saw the pictures.

You can still get it into stereo with crossed eyes, but it distracts from the 3D effect and I don't think it would work with a stereo viewer or anaglyph.

Next, the 70mm full frame front for this close up with the on‑axis pinhole.

With the camera oriented vertically and the shutter rotated, here's the First National Bank building with the rising pinhole.

Just down the block, the Oshkosh Public Library with the camera horizontal, again with the rising front which of course required the shutter to be rotated back.

Later the 55mm stereo front went back on to try out the rising pinholes. The divider didn't bend as much this time, but the left image is still a little bigger than the right.

The great oaks at the Merrill Soccer Field.

The passage between Merrill Elementary School and Gym.

The shutters operated well, the film transport was smooth and it was easy to change the fronts. I'll have to see what can be done about keeping that divider straight and give it another try.

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