Pinhole (in)consistency

The trials and tribulations of using multiple DIY pinhole cameras to produce consistent exposures across a single project.

My ‘best’ pinhole images, in terms of how I perceive the way others appreciate them, have usually been made with my commercially produced Harman TiTAN Pinhole Camera. For myself, however, the images I find most satisfying to create are those made with DIY pincams created from boxes, cans and bits of card or foamcore with a true pin hole punched in foil or sometimes directly into the material of the camera.

Amongst the seemingly endless proliferation of commercially made pincams all with accurate, etched or laser-cut pinhole apertures the aesthetic of what I think of as true pinhole images is becoming lost in the quest for detailed resolution and sharpness. What I seek from a pinhole camera is a serendipitous softness in which light and time create something unseen by the naked eye.

However when multiple cameras are being used to create several discrete images which will ultimately be presented as one, the serendipitous nature of the DIY pincam has to be somewhat controlled in order to achieve a degree of consistency.

The 8xIllyCoffeePincam

For the past few months I’ve been working on the idea of using eight coffee cans to create what I imagine to be a circular, overlapping 360ยบ presentation of the images made in each pincam. The assembled 8xIllyCoffeePincam is shown above.

Each can is fixed to a circle of plywood which has a tripod quick-release plate bolted through its centre. The interior of each can has been sprayed with flat black paint and the lids have been lined with a strip of black felt. The cans are made of steel and two holes have been punched directly through the side of each with a regular dress-making pin. Exposure time is controlled by a strip of black electrical tape. One aperture is positioned centrally on the vertical and the second is one third up from the bottom. This second aperture enables a raising of the horizon line (or lowering if the camera is positioned upside-down!) recorded on the image, i.e. the same effect as lowering or raising the front standard on a large format view camera. Because the media (paper or film) in the can is curved, using the lower aperture will also cause the horizon in the image to bow depending on the width and curvature of the media.

My idea is to select a position to locate and level the camera and then to evaluate and record individual images, one at a time, with each of the eight pincams. I’ve experimented with the camera before, each time resulting in a few tweaks and a refining of my technique as a result. Now I need to know if these refinements are enough for success.

For this outing I had the camera positioned fairly centrally in Aberdour Harbour at low tide on a bright afternoon. Each pincam was loaded with a 5×4 sheet of Harman Direct Positive paper mounted vertically and the lower aperture was used to raise the horizon and include more foreground than sky. I used the Pinhole Assist iPhone app to determine each exposure, assuming that the aperture in each can was around f/150 and by holding my iPhone directly above and perpendicular to the central view of each pincam.

Here are the eight images that I recorded. Although each exposure was measured in a consistent manner, it is plainly obvious that my assessment of the size of each aperture was far from consistent. Only one or two (E and SE) were anywhere near accurate and even so they are underexposed by at least a stop.

To resolve the problem, I need to do two things:

  • Reassess and adjust each aperture to get all of them as near as possible the same.
  • Review how I measure each exposure.

Starting with the pincam used for the ‘E’ image, I took a standard dressmaking pin and marked it with some tape at the furthest point it penetrated the pin hole. I then went round each pincam to make comparison and was actually quite surprised at the range and amount of adjustment needed on each pin hole! The aperture on the pincam used for image ‘N’ was by far the smallest, confirming the almost non-existant image produced.

Having made the necessary adjustments I then had to establish the actual diameter I now have in each can. For this I took a piece of aluminium drinks can and with the same pin punched a hole up to the marker. I scanned this alongside a metal rule at 9600dpi and made relative measurements of the full size image on screen. On screen, the pin hole measured 25mm in diameter and a 5mm section of the rule measured 217mm. Simple arithmetic then determined my actual pinhole diameter to be 0.576mm. Measurement of the paper in the can showed the projection distance to the centre as 80mm. This produces an effective aperture of f/138 centrally.

For future outings with the 8xIllyCoffeePincam I will assess exposure using a spot meter to measure the deepest shadow in which I want to record detail and reduce the exposure given for that by two stops thus placing the shadows on zone III with mid greys falling on zone V. (NB: This is a very much simplified implementation of the Zone System and should not be followed without greater understanding of the system’s complexity). For convenience I will base the exposure on f/128 with a bit added for the sake of serendipity!

Now, confident that this time I’ve got it right, all I need is another fine day to go try it all out, again.