Musings on pinhole photography

If you’ve been reading this blog, you know that last week I returned from the 2023 Burning Man festival in northern Nevada. It was a terrific event, full of excitement and artistic energy – until it rained. Then it became a less than wonderful mud bog. We managed; we survived; we will return next year and try again.

My camp is called the Pinhole Project. Our artistic endeavor is to document the art installations at Burning Man using large pinhole cameras on photographic paper. For this we have 10 55-gallon Kraft paper barrels, each with metal plates glued inside, and each with a precision-cut pinhole aperture in a sheet of aluminum that is cemented into the side of the barrel. On top of each pinhole is a “shutter” made out of gaffer’s tape.

We insert a large sheet of photo paper into each barrel in our darkroom – built inside a 20-foot container cargo box – and hold that paper in position with magnets. We then put a steel lid on each barrel, making the entire thing light-tight. Once loaded with photo paper, the cameras are ready for the field.

Every morning we hold a public workshop in our gallery. Interested people show up, sometimes in surprising numbers. We explain how the cameras work, how we develop the photos, and how we re-photograph each finished photo for our digital archive. At the end of the workshop, we invite those present to join us on the Playa to make new photographic images. We have a big pick-up truck for transporting the cameras.

The photographic paper we use is made by Foma in the Czech Republic. It’s designed for use under an enlarger in a darkroom, so the ISO is not published. But we have a Weston Master V light meter and we have used it to estimate the paper’s ISO at about 0.3. This requires a long exposure in the bright sunlight of the Black Rock desert. Our typical exposure time is about 45 seconds.

If people will be the subject of a pinhole photo, those people must stand still for 45 seconds –which is very difficult. We do our best, and the results are very impressive.

One day I took the group out onto the Playa to make photos. I had an idea I wanted to explore. There was a huge sign erected on the Playa saying “NO DANCING” – and I decided to take a large pinhole photo of a bunch of people dancing in front of that sign. It was a simple photo to organize, moving people into place, moving the camera to the right spot. We use wooden camera supports that look like medieval torture devices; each is a plywood piece with teeth on each side. There are two level edges for each tooth so that the large barrels can be placed in a number of positions on the support. We often add a bungee cord to stabilize the camera in wind.

The No Dancing photo turned out very nicely, and I am very proud of it.

A couple of days later I went back out on the Playa with a friend and we took three more large pinhole photos. Mine was a horizontal portrait of three inflated spheres of the Earth, the Moon and Mars that were on the edge of the Playa. These works were exceptional. They were printed on Mercator sections of fabric, then sewn into complete spheres. Illuminated at night, they were a spectacular sight.

I set up the camera and took a one-minute exposure –it was slightly overcast. Then we moved on to take a couple of other images.

Back in the darkroom, we processed all that day’s images, and mine looked very nice. But Mars had an egg shape, a significant distortion of its otherwise spherical shape. I knew this had not been caused by wind, so I assumed it was a camera distortion. Occasionally we have a sheet of photo paper fall inside the barrel when a magnet isn’t placed correctly. This usually causes blockage of part of the image, but it doesn’t cause distortion.

I needed to understand why this distortion was there.

I have drawn two pinhole cameras here: one is the camera we use at Burning Man. It’s a Kraft paper 55-gallon drum with its pinhole aperture on one wall of the camera. The other is an idealized pinhole camera that has its aperture at an optical center that is equidistant from all points of the photo material.

The current camera is far from ideal in terms of its optical path. Light coming in on the edges travels slightly less than half the distance that light travels in the center of the image. I am pretty sure this explains the distortion. The light along the outer edges of the image is traveling much less than the light in the center, and thus, it is being distorted along one axis. The other axis is affected similarly, but to a lesser degree because it’s a smaller difference between the center and the edges of the photo paper.

The idealized pinhole camera would be pretty easy to make and test. I might try it by inserting a modified film plane into a barrel to normalize the distance that the light travels after it enters the camera through the aperture. With that I am quite sure that optical distortion would be eliminated on the circumferential axis.

I’ll keep you posted!