A Non-Silver Manual: Pinhole photography

The chapter called “Pinhole photography” of Sarah Van Keuren’s book “A Non-Silver Manual: Cyanotype, Vandyke Brown, Palladium & Gum Bichromate with instructions for making light-resists including pinhole photography”.

Read the previous section of this book.

All non-silver processes require light-resists or negatives that are the size of the final image. A darkroom enlarger does not project enough actinic light through a negative to even begin to expose paper coated with cyanotype solution, no matter how long the exposure. The closest I have come to making a non-silver print through enlargement was by putting a black-and-white negative in a slide projector about 12 inches from paper sensitized with vandyke solution. After 40 minutes a faint image printed out.

A large negative suitable for contact-printing in non-silver can be made in one step using a pinhole camera of appropriate design.

There is little or no financial barrier to becoming a pinhole photographer. Anything that can be turned into a dark chamber will serve as the body. No lens is needed for a pinhole camera. Instead, a lensless aperture allows light into the camera obscura (dark chamber) to form a latent image on film or enlarging paper.

Pinhole photography demonstrates basic principles of photography such as how the shape of a camera affects the rendition of a subject on film. The relationship of film size to focal length can produce images ranging from extreme wide angle to extreme telephoto. (And then there are all the distortions that can occur when film or enlarging paper is curved, angled, folded or crumpled within the camera.)

The durations of pinhole exposures are usually measured in minutes instead of in the fractions of seconds we are accustomed to with lens cameras. These longer exposures seem like dashes rather than dots in the grid of time and space. When a person poses for minutes at a time, various expressions of the face and subtle movements of the body are conflated onto a single sheet of film. The resulting image may be more akin to a drawing or painting done over time than to a split-second exposure.

Against a dark background a figure can be recorded on film in a number of poses and slow movement can be seen as a blur. Fast movement is invisible except for specular highlights (such as light glinting off metal jewelry) that record as lines. The ultimate specular highlight is the sun, which can be used as a bold drawing instrument by moving the pinhole camera quickly in front of it in a sort of sun dance. The slow paths of the sun across the sky, day after day, can be recorded on extremely slow light-sensitive material, as student Nat Hamilton did a few years ago on paper sensitized with vandyke brown solution in a pinhole camera aimed upwards. Gaps in the paths indicate cloud cover and provide a succinct record of the weather — as long as the pinhole remains unobstructed by rain, snow, etc. Dominique Stroobant recorded the paths of the sun for as long as 6 months on one piece of film (see Pinhole Journal Vol. 4, #2, 1988).

If, during the pinhole exposure of a sunny landscape, a cloud floats in front of the sun, exposure time may have to be prolonged. The combination of highlights gilded by the sun and shadows illuminated by diffuse cloudy light can produce a negative with a sculpted fullness that sun or cloud alone could not reveal.

If no cloud floats in front of the sun, a hand mirror can be used to reflect the sun into areas that need illumination. And indoors, when making pinhole exposures onto panchromatic film that responds to yellow light, a hot light (such as a 500W tungsten or quartz lamp — with ‘barn doors’ to control the direction of the light) can be moved selectively over the subject. A mirror directing the reflected light of the sun onto parts of the subject outdoors and a hot light moving over the indoor subject are both ways of painting with light.

The soft focus and infinite depth of field in a pinhole negative tend to fuse figure and ground. There is no focal plane but instead a tapestry of tonal values out of which forms emerge. Sometimes it may enhance and even change the meaning of a pinhole image to hold a sheet of cloth behind the subject for at least part of the exposure. (In a print called ‘Passage of Time’ I held a light gray cloth in front of a bank of blooming flowers for a fraction of the exposure to boost flowers’ tonality into a lighter range of values but let withered foreground flowers that were past their prime receive normal exposure and thus print darker. To me this conveyed bright summer followed by autumn.)

How It Works

Pinhole photography may seem a mystery until certain facts are understood. An illuminated object reflects light in all directions, including some light that enters the pinhole aperture. If the subject is a white tulip in a matte black vase, reflected light from the tulip that enters the pinhole will continue traveling in straight lines and will form a latent image on the film that, when developed, will be an almost opaque, dark, upside-down tulip rendition on the film. The matte black vase will not reflect much light and that absence of light will record as mostly clear film in the shape of an upside-down vase at the top of the sheet of film. It follows that light reflected from an illuminated landscape will enter the pinhole from all angles and continue through the tiny aperture in straight lines to expose film or enlarging paper in the camera. An inverted and laterally reversed image will be formed on the film, the same as in a lens camera.

Many people associate pinhole photography with images produced by the traditional cylindrical oatmeal box camera. These are wide-angle renditions that are further distorted by the curvature of the film in the camera so that the subject swells in the middle (where the light has the furthest to travel and the rays of reflected light spread the most) and tapers toward the edges (where it has less distance to travel and spreads the least). But it is just as easy to make a pinhole camera that gives a ‘normal’ view of the subject like the kind obtained with a 50mm lens on a 35mm camera. For instance, a cardboard carton loaded with flat 8 by l0 inch film (or enlarging paper) that is 12 inches from the pinhole would give such an undistorted view. The 12-inch pinhole-to-film dimension equals the diagonal measurement of the film in the camera. If the focal length were reduced, a view tending towards wide angle would result. An increased focal length would tend towards a telephoto rendition.

Building the Camera

A simple pinhole camera can be fabricated in less than 5 minutes. A very serviceable pinhole camera can be made out of a brown corrugated cardboard carton. If you are planning to expose ordinary black-and-white enlarging paper or an orthochromatic sheet film that does not respond to warm brown tones, you don’t need to paint the brown carton black inside, or line it with black paper. But if you will be using panchromatic film or paper, the interior should be matte black to avoid fogging from reflected brown light.

You will need to tape corners and cracks with opaque tape and fashion a lid (if the carton only has flaps) that generously overlaps the sides of the carton. Some sources recommend black electrical tape, rather than black photographic tape, to make a pinhole camera light-tight. This kind of tape is satisfactory under many conditions of moderate-to-low light, but if the camera is given prolonged exposure to intense light, the film inside it can be fogged by light leaking through the electrical tape. (To demonstrate the difference between the two, look through a dark tube at squares of electrical and photographic tape, side by side on a light table. While no light is visible through the photographic tape, there are so many tiny openings throughout the electrical tape that it looks like a starry night sky. It is worth using the more expensive black photographic tape or else use multiple layers of electrical tape.)

When making a shallow wide-angle camera, use about one square inch of pinhole metal and cut a window in the camera that is just a little smaller. This generous expanse of metal will allow rays of light entering the camera at oblique angles to travel straight to the film instead of being blocked by the relatively thick edges of your container (which can vignette your image with an amazing magnification of the container’s edge). With such a camera, especially if aluminum has been used, it is a good idea to darken the pinhole metal that faces inside to prevent light from bouncing off the film onto the metal’s reflective surface and back again, fogging the film. This can be done with black photographic tape, ideally before installation of the pinhole, pressing the tape down carefully and leaving just enough room around the pinhole to admit light from all angles.

Make a shutter for your camera out of black tape with one end folded upon itself to form a tab for easy removal. To keep the pinhole aperture free of stickiness and dust, place a small piece of the black tape face down on the sticky part of the shutter tape where it would actually touch the pinhole. Make sure that the rest of the shutter has enough tack to hold it down around the pinhole. I had the disappointing experience of making pinhole exposures on a mountain in New Mexico and then discovering that a piece of lint had been blocking the aperture. Now I am careful to take a peak through my pinhole to make sure it is unobstructed before each exposure.

Framing the Subject

Light travels in straight lines through the pinhole and onto the film. Therefore, going in the opposite direction, the pinhole photographer can ascertain what will be recorded onto the film by extending lines from the corners of film in the camera through the ‘pinhole plane’ and out into the subject. (The pinhole plane is the center of the front edge of the camera if the pinhole is in the center of the box.) If the subject is close to a pinhole camera mounted on a tripod, a rod may be laid along sightlines drawn on the top, bottom and sides of the camera and the rod can be extended into the space of the subject, actually touching points on the subject that will indicate the boundaries of the image. When framing a large subject such as a landscape, the photographer can look with one eye along drawn or studded sightlines on the camera to gain an idea of what will be included on the negative.

Image Resolution

With the pinhole camera there is no focal plane, no area in the image on film that appears to be more in focus than a closer or further area. This means that foreground, middle ground, and background are recorded with equal softness. Bundles of light of varying intensity enter the pinhole and these disks of light, that are known as ‘circles of confusion’, accumulate to form a latent image on film. The circles begin to turn into ellipses as the angle of entry of bundles of light becomes more acute around the edges of pinhole negatives, especially in wide-angle pinhole cameras.

The size of the circles and ellipses depends on the diameter of the pinhole and the distance between pinhole and film. Rays of reflected light travel in straight lines from the subject through the pinhole and onto the film, but once inside the camera these rays spread so that a long distance from pinhole to film will produce a softer image than a short distance using the same size pinhole.

Fabricating a Pinhole

The word ‘pinhole’ is really a misnomer since the average pinhole is made using a small sewing needle. Brass shim stock is the metal usually recommended for making pinholes, but it can be hard to obtain. The flat portions of disposable aluminum cookware work as well, the only drawback being that internal reflections from the cooler, bluer aluminum affect blue-sensitive orthochromatic film more than the warmer reflections of brass shim stock. This can be overcome by darkening the inward side of the aluminum as described in the previous section.

Cut a piece of aluminum that is about one inch square with an old pair of scissors (or with a utility blade and straight edge) and lay the metal on a scrap of matboard. Using a thimble or a coin, position the needle perpendicular to the metal and gently push it through the metal onto the scrap of matboard. This initial piercing of the metal will produce a sharp burr on its underside. Sand down the burr with #400 silicone or carborundum paper or crocus cloth or some other fine abrasive. Next push the needle through from the sanded side and sand down the minor burr that results on the unsanded side. Then twirl the square of metal on the needle to make the hole as round as possible.

Hold the metal up against a strong light source to see if it admits one small circle of light. With a loupe or some other magnifying lens, examine the aperture to make sure it is free of debris. To understand how pinhole cameras have such great depth of field, try the following: hold this page of text at a comfortable reading distance; then bring the page so close to your eyes that it is out of focus; now hold the metal with pinhole against one eye, shut the other eye, and read the page up close. The tiny pinhole is the ultimate ‘shut down’ aperture that gives maximum depth of field.

You don’t have to get too fussy about pinhole size, especially in the beginning. Part of the fun of making a pinhole camera is its low-tech simplicity and latitude. But for those who want optimal pinhole resolution, a table from Pinhole Photography: Rediscovering a Historic Technique (3nd Edition, 2004) by Eric Renner and Nancy Spencer (see Recommended Periodicals & Books in “Resources”) lists on page 162 the optimal pinhole diameters for different ‘focal’ lengths (the distances between pinhole and film). These optimal diameters produce circles of confusion that overlap by about 30%, an amount that is thought to give the best image definition possible with a pinhole.

It is fairly easy to make pinholes of different diameters with one tapering needle. To make an especially small pinhole aperture, approximately .15mm in diameter, pierce the metal with the tip of the needle from both sides and twirl it right on the tip of the needle. To make a larger pinhole, push the metal square onto the shaft of the needle from both sides and twirl it on the shaft. By using the tapered part of the needle, it is possible to make pinholes in sizes that fall between these extremes.

The diameter of a pinhole can be measured, crudely but effectively, with a millimeter ruler. Place the left edge of the pinhole aperture under a metric ruler so that it bisects the black line marking one of the millimeters. Using a loupe, estimate in tenths how much of the millimeter the pinhole spans. Write the aperture’s diameter on the square of metal. The metric system is more convenient in determining the f/stop or speed of your camera.

Calculating your f/stop

Calculate your f/stop by dividing the pinhole diameter into the focal length of your camera. (It is a nuisance to try to divide 9 inches by 1/64 of an inch compared to doing it quickly on a calculator with metric measurements.) The resulting number, usually in the hundreds, will be the f/stop of your camera with that particular pinhole. If you know the f/stop of your camera you can refer to a table on page 193 in Renner’s Pinhole Photography (3nd Edition) to get a rough idea of what your exposure time might be with films of various ISOs under various lighting conditions. Renner’s 2nd Edition has a more comprehensive chart on page 145 that ranges from noonday sun on sand or snow — to the dim light of dawn or dusk.

Speed of Film or Paper

At UArts, we are sad to have used up a donated supply of Commercial film, a slow black-and-white orthochromatic film (used with a red safelight) with rich continuous tone. Commercial film is still available through Ilford in 8 by 10 inch format for nearly $4 a sheet, but this is a bit steep for students. Less expensive Arista-II Ortho Litho Film (see “Making Enlarged Negatives” for description and also ‘Freestyle Photographic Supplies’ in ‘Resources”) works well enough in pinhole cameras rated as ISO 32 and is easy to use with the above-mentioned chart in Renner’s 2nd Edition. Enlarging paper is also an option. It is slower, usually rated around ISO 8 but in my experience it is somewhat faster than that. Resin-coated multigrade paper with a pearl or matte surface (less reflective than a glossy surface inside the camera) is a good choice. Since multigrade paper is sensitive to green as well as blue light, foliage is rendered with more detail than with graded paper. (Also, when printing in non-silver processes, exposures through rc paper are shorter than through fiber paper and can be made even more so by pulling the paper base away from the rc image.) It should be mentioned that all of these materials, used inside pinhole cameras, respond very slowly to incandescent light. (Artist Phil Simkin devised a project at the Philadelphia Museum of Art back in the late 70s in which wide-angle pinhole cameras loaded with paper negatives were given to museum visitors to take home and use to record their home spaces. The recommendation for an indoor exposure by incandescent light was for about 20 hours while for an outdoor home space illuminated by direct sunlight it was 15-40 seconds.)

Working by trial and error, you will develop a heightened awareness of the magnitude of light, perhaps even sensitivity to your pupils shutting down or opening up. This approach works best if you stick with one pinhole camera with one aperture. A useable negative should be obtainable in three tries without any charts. There’s a lot of latitude with pinhole negatives, especially if you are printing from them in gum bichromate.

There’s even more latitude with pinhole negatives now that ordinary people own flatbed scanners. Paper negatives are very easy to scan. Nearly invisible shadow details appear and can be strengthened in Photoshop. Even if you don’t have a transparency lid, film negatives backed by white paper can be scanned in the reflective mode. Digital negatives can be produced by a desktop printer (inkjet or laser) or by an imagesetter. See the ‘Desktop Negatives’ segment in the next chapter, “Enlarged Negatives”.

Desktop masks may be prepared to use in conjunction with original pinhole negatives to keep some areas from getting exposure as you print the other parts of the negative.

If you work in layers of color as a painter or printmaker, ‘Layers’ in Photoshop is suited to a way of thinking that you already grasp. You can produce a number of different digital negatives to print in different colors from a single pinhole negative, and you can view a rough approximation on your monitor of how they would print together.

Developing Pinhole Negatives

Paper developer works well for black-and-white pinhole negatives, both paper and film. It is more active than most film developers and provides the extra highlight density needed for vandyke and palladium.

At home in total darkness I develop panchromatic 8 by 10 inch Tri-X pinhole negatives for 21/2 – 3 minutes, in paper developer. Immersing and agitating each sheet of film in a tray of room temperature water before slipping it into the developer helps prevent developer lap marks, especially in gray areas. After fixing, immersion in a hypoclearing agent will shorten washing time. The refinements of presoak and hypoclearing are not practiced in our non-silver darkroom at UArts, I must confess, and most of the time the negatives are fine, but I found with my own Tri-X pinhole negatives of sky, sand and water that these steps produced better negatives. See “Enlarged Negatives” for more information.

Read the next section of the book.

Post a Comment

Your email is never shared. Required fields are marked *


WordPress SEO fine-tune by Meta SEO Pack from Poradnik Webmastera
%d bloggers like this: