Margaret D. Andrews
The first camera was conceived as a sketching aid sometime in the early 1600s. It consisted quite simply of a dark chamber with a small hole at one end, through which light was projected onto the opposite interior wall. There an inverted image of the outside scene was formed, which an artist, working inside the camera, traced. The inventor of this dark chamber, or camera obscura, is not known but it is certain that Aristotle was familiar with the principle and Leonardo da Vinci made precise drawings of the camera obscura.
Later models were built on sedan chairs or on wheels for mobility. About 1660, a compact model was designed, with a lens instead of a hole and an interior mirror to reflect the image onto the ground glass screen.
Some 60 years later, in 1727, Johann H. Schulze, a German physicist, discovered that silver salts are sensitive to light. A century passed before Joseph Nicephore Niepce, a French scientist, made use of that discovery to take the first photograph.
Louis J. M. Daguerre, a partner of Niepce, went on to develop a more efficient process of photography which he announced to the world in 1839, it was called the Daguerreotype.
The camera obscura today is more important than a clever sketching device. A periscope, for example, is basically a form of the camera obscura, as is the viewing mechanism on a single-lens reflex camera. In its basic form, however, the camera obscura, with a sheet of tracing paper, provides an entertaining way of transforming even the most hesitant sketcher into an artist. And in the form of a pinhole camera, which today uses fast modern films, it furnishes an instructive basic aid for learning the fundamentals of photography.
The Camera Obscura
Materials:
heavy rigid cardboard
magnifying glass
small mirror
pane of frosted glass or plastic
black masking tape
ruler
pencil
craft or exacto knife
The dimensions of the camera obscura are determined by the focal length of its lens; so, in listing the materials needed, l can only approximate their measurements. More on the subject of focal length in a moment.
The magnifying glass should be round and no less than 2 inches in diameter. In general the bigger the glass, the brighter the image. If you already have a large, expensive glass, the ideal kind, you can use it as a detachable lens without damage to it or its frame. More practical, however, and nearly as good would be a smaller, drug store glass.
The mirror could be the nonmagnifying side of a small, round shaving mirror or something similar, 3 to 6 inches in diameter.
Use heavy cardboard to construct a solid, rigid box. Double or triple thickness matteboard is excellent.
A good glazier can supply the ground glass screen. Ask for ground glass or frosted glass, the kind that appears to have been sanded on one side. A fair size pane should cost less than a dollar. An acceptable substitute is a sheet of clear plastic frosted on one side.
Position the magnifying glass between some bright object, such as a lamp, and a sheet of paper. Slowly move the glass toward the paper. When the glass is close enough, it will produce an inverted image on the sheet. As the distance between glass and paper changes, the clarity of the image varies. When the image is at its sharpest, it is said to be in focus. This distance is the focal length of the lens.
In terms of shape, a camera obscura is a cube, each side of which is equal to the focal length of its lens (the magnifying glass, that is). Thus, before building a camera obscura, you must first determine the focal length of your glass. To do so, produce an inverted image as you did before, this time with a ruler placed as in figure A to measure the exact distance between the glass and the paper.
(figure available in print form)
Focus on an object about 12 to 15 feet distant. The focal length depends not only on the size of the magnifying glass, but also on the distance between the object and the sheet of paper. Because the camera obscura will be nonadjustable, it must be built with a compromise focal length as its basic dimension. An object 12 to 15 feet away will yield a workable average focal length.
You will probably determine the focal length of your magnifying glass to be between 6 and 12 inches. Whatever is is, you will use that measurement to determine the length and width of each side of your camera obscura, which, as I have noted, will be a cube. The focal length of my glass, which was 2 1/2 inches in diameter, was 8 inches.
I thus determined the dimensions of my camera obscura: 8 inches by 8 inches by 8 inches. If the focal length of your magnifying glass is different, the of your camera obscura will be different.
Of the six surfaces of the camera obscura, four (the two sides, the back, and the bottom) will be solid cardboard, with no openings. The fifth surface (the front) will also be cardboard, but will have an opening large enough to accommodate the lens. The sixth and last surface (the top) will be the ground glass screen.
Let us consider the four solid cardboard surfaces first. If you prefer working with individual pieces of cardboard, cut four squares, each measuring one focal length by one focal length (8 inches by 8 inches, in my case). If, as I did, you use one large piece of cardboard, cut out a patter of four adjacent squares, clustered in the form of a T. Again, each square should be one focal length by one focal length.
To facilitate fitting separate squares together, bevel edges with an exacto knife. If you cut out a T pattern, score the three edges of the center square that it shares with the three outer squares.
Fold the cardboard so that it assumes the shape of a square with two missing sides. Using black masking tape, first tape corners where edges meet; then tape the three folded edges for reinforcement. If you use four separate squares of cardboard, they are, of course, taped together the same way.
Cut a fifth square of cardboard, and determine its center by drawing its diagonals. If possible, remove the magnifying glass from its frame; place it over the center of the square, and trace its outline with a pencil. If you can’t remove its frame, trace the outline of the frame itself. Cut along the outline, and position the lens in the hole, taping it with small pieces of tape on both sides to keep it in place. Bevel the edges of the square, and tape it to the other three.
Measure the diagonal of a square; then cut a cardboard rectangle that length and slightly less in width (to allow for cardboards thickness) than one focal length. Tape the mirror in the center of this rectangle. Fit the rectangle into the box, with the mirror facing toward the lens. Tape it in place.
The ground glass screen, which should be the same size as the other squares, may now be placed on top, frosted side down. Before taping the edges, check the image by pointing the box at a lamp or window. If the image is dim, remove the screen and make sure its surfaces are clean. Painting the cardboard interior of the box flat black will brighten the image. When you obtain a satisfactorily clear image, tape the screen in place, and you are ready to trace the image you see.
Figure A: This sketch illustrates the way to determine the effective focal length of your lens, the magnifying glass. The distance between lamp and lens should be about 15 feet. Distance between lens and paper dictates the dimensions of your camera obscura.
(figure available in print form)
Figure B: This is a cross section of the camera obscura, showing the diagonal mirror. The distance from lens to mirror, plus the distance from mirror to screen, equals the length of one side of the square, one focal length.
(figure available in print form)
The Pinhole Camera
Materials:
black masking tape
1” square of foil
number 10 sewing needle
extra fine sand paper
14” by 26” black matte board
ruler
glue
exacto knife
pencil
candle
A pinhole camera is nothing more than a cardboard box with a pinhole “lens,” covered with a flap which acts as a shutter and a frame in the back to accommodate sheet film. Yet if you build one with care and precision, it will be a device enjoyable in itself, instructive in the fundamentals of photography, and capable of taking great pictures.
Cut a strip of cardboard 7 by 26 inches. With the ruler and pencil, divide the strip into four sections, as follows: 7 by 7 inches, 6 by 7 inches, 7 by 7 inches, and 6 by 7 inches. This strip will form the body of your camera (see figure C).
From the remaining strip of cardboard, cut four rectangles, each 6 by 7 inches. Set one rectangle aside for use later at the camera back. In a second rectangle, cut a hole about 1/2 inch square. Be careful to place the hole in the exact center of the rectangle; this is the spot where diagonal lines drawn on the rectangle cross.
In the center of one of the other two rectangles, cut a rectangular hole, 4 by 5 inches; in the center of the other, cut a smaller rectangular hole, 3 1/2 by 4 1/2 inches. You now have two cardboard frames: one inch wide, the other 1 1/4 inches wide (see figure D).
Place the wider of the two frames (the one with a 1 1/4 inch border) on a flat surface. If only one side of the cardboard is black, be sure the black side is face down.
Coat one side (either side will do) of the narrower frame with glue. Then position this frame, glue side down, over the wider frame, so the outside edges of both frames coincide. Press the frames together, and apply pressure for a few minutes until the glue begins to adhere. Wipe off any glue that oozes out and apply pressure until the glue dries.
This double thickness cardboard will be attached later to the camera back and will serve as a holder for the sheet film.
Making the camera body is simply a matter of folding the cardboard strip (the one measuring 7 by 26 inches) into the shape of a box. First, cut V-shape groves along the three lines dividing the four sections, to make the folding easier, and bevel the two 7 inch ends. Grooves and bevels should be on the black side of the cardboard. Fold the strip, and tape all four corners for reinforcement.
Tape the film holder (the two cardboard frames glued together) to one end of the camera body. The indentation formed by the two glued frames should face outward. Position the camera back (the solid 6 by 7 inch cardboard rectangle) over the film holder, black side facing inward, and tape one of the 6 inch edges to the camera body to form a hinge. A small piece of tape attached to the other 6 inch edge will keep the back closed when the camera is loaded with film.
To the other end of the camera body, tape the camera front (the 6 by 7 inch cardboard rectangle with the 1/2 inch share hole in it). Again, the black side should face the interior.
Place the square of aluminum foil on a soft, flat surface, an old newspaper on a tabletop will do. Pierce the center of the foil with a No.10 sewing needle. Do so carefully and slowly. A piece of tape attached to each side of the foil will help in making a smooth, round hole; later, the tape is discarded. Sandpaper the dimpled side of the pierced foil to remove the tiny burrs. Then work the needle through the hole again, this time about halfway up it shank (see figure E).
Blacken both side of the foil by passing them over a candle flame. Position the pinhole, the dimpled side facing inside, over the center of the hole in the camera front. Tape the foil in place. Cut a 3 inch square of cardboard; center it over the pinhole, and hinge it along the bottom with a strip of tape. This is the shutter. A small piece of tape at the top will keep it closed when the camera is not in use.
Load the camera with 4 by 5 inch sheet film in an absolutely dark room or closet. When loading the film, be sure the notches in the sheet are at the upper left corner of the camera (Figure F); that way, you will know the emulsion side of the film is on the inside, as it should be.
To take a picture lower the front flap briefly. This exposes the film. In bright sunlight, with fast black and white film such as Tri-X Pan, try an exposure time of one to two seconds; in bright, overcast weather, increase time to two to four seconds. With color negative film, triple the time. If possible bracket an exposure by taking two more shots, one at half and one at double the initial time. At first, you will guess times; later, when you have developed your first photographs, you will have a standard by which to estimate exposure times accurately.
During exposures, keep the camera steady by taping or weighing it down. Still lives and landscapes are excellent subjects; they provide the soft, dreamy quality characteristic of the best pinhole photographs.
Figure C: A strip of cardboard, 7 by 26 inches, will be folded to form the camera body. Two 6 by 7 inch rectangles, one with a small hole in its center, will become the front and back.
(figure available in print form)
Figure D: Two 6 by 7 inch rectangles form the I film holder. In one, cut a hole 4 by 5 inches; in the other, cut a hole 3 1/2 by 4 1/2 inches. Glue the two pieces together, making a frame to hold the film.
(figure available in print form)
Figure E: Pierce the foil slightly at first; then sandpaper the burrs off the dimpled side. Next, work the needle about half its length through the foil to produce and even, round pinhole. Careful, precise work is critical because the pinhole acts as the lens for the camera. If the aperture is too large, the image will not be as sharply focused.
(figure available in print form)
Figure F: The notches in sheet film help position it in the dark: they should be at the upper left corner of the camera. In the field, use a large loading bag, available from a photographic supply store, when you load film.
(figure available in print form)