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A stenopeic camera is basically a dark box with a small hole in one of its sides and a photosensitive material in the opposite side. The mechanism of this box is very simple. The hole is responsible for selecting a single ray of light from the many that the subject reflects, so that the others are rejected and only one reaches the photosensitive surface, forming a point of the image. The possibilities to create a stenopeic camera are very varied. They can be made from very common elements, preferably with shapes similar to a prism or a cylinder, such as a shoebox, a can of cans, etc. We can also build it from a camera that has been removed from the optical system. The basic elements to build our stenopeic camera are not the same as those of a conventional camera. To build it, we will need a shoebox or similar, of a different size. Depending on this size, we will get different viewing angles. The viewing angle of a camera is called the coverage angle. We can also use a metal box, such as this cookie box, which will give us a coverage angle of 360 degrees. We can use wooden boxes, very useful if we want our stenopeic camera to last a long time, can of cans or gift boxes. The important thing is the rigidity of the camera and that it is, if possible, black. To make our stenopeic camera, in addition to a box, we will need matte black paint in spray or brush. The important thing is that it does not generate shine. With it, we will paint our box to prevent the light from bouncing inside. Scissors, cutter or cutting material. A meter, a ruler to make measurements, as well as a calculator. We will also need brass, aluminum or baking trays. From them we will cut a small piece that we will use to make the stenope. We will also need a metal sandpaper and black insulating tape. Finally, we will use tape to insulate windows, which will not be very useful to block the light in those boxes that are not very rigid or in places with risks of light entry. Later we will paint it, as well as the box, with black paint to make sure that no ray of light is filtered. For the manufacture of the stenope we will need hypodermic needles or sewing needles. The hypodermic needles are very functional, as they are calibrated surgically. You can buy them in any pharmacy, ranging from 0.4 mm to 1 mm. Sewing needles are calibrated with a number. Each of these numbers corresponds to a thickness in millimeters as shown in the table. They are not highly recommended, since most of them are imported from China. These numbers do not fit too well to the millimeters. To make the stenopes in more rigid materials, we will use a drill for models of the Dremel brand or similar. A 0.4 mm drill or the size necessary to drill metal. Finally, to check if the stenope is well made, we will use a thread counter with which we will be able to appreciate the quality of it. The first thing we have to do before making the stenope is to decide where we are going to make it. Keep in mind that a box has multiple sides in which we can place our stenope. Depending on where you place the stenope, the camera will have a different coverage angle. The coverage angle of a camera will determine the information that this sample shows. Being the cameras with a very narrow coverage angle, telephoto lenses. And the cameras with a very wide coverage angle, wide-angle lenses. The coverage angle will be determined by the focal distance of the camera, which is the distance between the stenope and the focal plane of it. The focal distance is inversely proportional to the coverage angle. The greater the focal distance, the smaller the coverage angle. A camera with a long focal distance will be a telephoto lens. On the contrary, a camera with a short focal distance will have a very wide coverage angle. It will have a very wide coverage angle, in this case we will have a wide-angle lens. If the camera were square and the focal distance the same as the width of the focal plane, the coverage angle would be 45 degrees, which we call a normal lens, more or less the vision of the human eye. Once we have decided where to place our stenope, we will have to draw the geometric center of that side of the box. We will draw a vertical line and another horizontal line, using a ruler or a meter. Then we will mark a window of approximately 2 by 2 centimeters or 4 by 4 centimeters. We will use a cutter to make the cut of that window, trying not to leave cardboard burrs on the edges of the cut. If necessary, we will sand the profile of the box. Before painting the black box, it is convenient that we isolate the most critical areas to the light, using tape to isolate windows. If the box is black, it will not be necessary to paint it. To paint our box, it is best to use matte black spray and another larger box with which we will avoid staining. The spray must be applied uniformly, keeping the boat in a vertical position about 25 centimeters away. The boxes look very nice if they are painted on the outside, but let's not forget that the interior is the most important part, since it is there where the light can bounce. The stenope is undoubtedly the most important part of the stenope camera. A good way to do it is to use an aluminum tray for the oven. From this tray we will cut a small portion and on it we will draw a square one centimeter larger than the window cut in our box. In our case, our window measures 4 by 4 centimeters, so the square must measure 5 by 5 centimeters. To this square we will mark the horizontal and vertical, also looking for the geometric center. Later we will cut it with a cutter. Having cut the metal piece of 5 by 5 centimeters, the next step is the drilling of a stenope. The diameter of our stenope will be determined by the focal distance of our camera. We will continue to find it using the following formula. The optimum diameter of the stenope will be the square root of the constant 0.0016 times the focal distance. In the camera we are making, the optimum diameter is 0.5 millimeters. Before drilling the stenope, it is convenient to make a soft surface on which to support the metal plate, so as not to bend the needle. Then we go to drill the plate with our needle very carefully and keeping it in a vertical position. When we have drilled, we will gently pass a sandpaper on both sides, eliminating the metal burrs that may have remained. We can check the quality of the stenope made using a thread counter magnifier or by putting the piece against the light. To place the metal piece in the camera, we will use as a reference the vertical and horizontal marks of both the box and the metal piece. To hold the plate we will use black insulating tape. The shutter will also be made using black insulating tape, to which we will bend one of its ends in order to be able to open and close the passage of light through the stenope. Our stenope camera is already made, but to calculate the exposure of a shot we will need to find the number F of it. The number F will be the result of dividing the focal distance of the camera, in our case 220 mm, between the optimal diameter of the stenope, in our case 0.5 mm. 220 between 0.5 will give us 440. The number F of our camera will be 440. The exposure calculation will be done using a reflex camera with a photometer. We will position this camera with a point of view similar to that of our stenope camera, pointing to the measurement that it gives us. For this example, our measurement has given us a number F4, a speed of 1.250 and an ISO of 100. We will place the measurement made in the table of numbers F, times and sensitivities. In this way we will be able to easily calculate the necessary exposure for our shot. We must bear in mind that the sensitivity of our paper is 6 ASA, while the sensitivity that we have marked in the camera is 100 ASA. The difference from 100 to 6 is 4 negative points. To compensate for these minus 4 points, we will move the shutter time 4 positive steps. Since we were in a 1.250, we must move the time to 1.15, plus 4 points. Next, we must adjust the number F of the reflex camera to the number F of our stenope. The number F of the measurement was F4 and the number F of our stenope was F440. However, we will adjust to the number F closest to the scale, which is F360. From F4 to F360 there are minus 13 steps. To compensate for the current lack of light, we must add to the time plus 13 steps, starting from the position in which we were, 1.15. 1.15 plus 13 steps gives us 512 seconds, the final exposure time. Here is the number F, the time and the final ISO of the exposure with which we will make this shot for our stenope. www.ottobock.com