Can a black box be used as a photographic tool?

Pinhole camera Pinhole camera, also called photographic camera box, is the prototype of the camera. Its basic part includes (1) a sealed camera box, followed by a focusing screen; (2) A small hole or a converging lens is arranged in front of the sealing box.

The light emitted by the object, after passing through a small hole or lens, produces an inverted real image on the focusing screen of the sealed box. The tiny space makes the light of each point of the object only reach its own image point without overlapping, thus obtaining a clear image. The smaller the pinhole, the less light passes through the pinhole and the lower the brightness of the image.

According to the principle of pinhole imaging, a pinhole imager can be made and a clear image can be seen on its screen. If you put a photosensitive film on the screen, you can take a clear picture and become a pinhole camera. However, this requires a "shutter" and a slot for loading negatives. In addition, the requirements for sealing are stricter than those for making ordinary pinhole imagers.

The structure of pinhole camera is shown in Figure10.6-L. The camera body is made of toilet paper and is divided into two parts: the front cover and the back cover.

manufacturing method

Draw it on the toilet paper according to the size of figures 10.6-2, 10.6-3, 10.6-4 (δ is the thickness of toilet paper), cut it along the solid line of each figure, and then gently carve it with a knife along the dotted line. Don't cut through, so when you bend, you will break a straight edge. Then paint both sides of each block black.

Bend the cut front cover outer layer development drawing (Figure 10.6-2) by 90 degrees along the dotted line to form a five-sided paper box, and stick it with adhesive tape. Then stick a piece of 120 film black lining paper on one side with a round hole, and tie a small hole with a diameter of about 0.4 mm on the lining paper in the center of the round hole with a needle (the diameter of 12 sewing needle is about 0.4 mm). Then, as shown in figure 10.6- 1, stick a paper slot on the edge of the small hole and insert a hard paper strip in the paper slot, which can be used as a blind and keep the small hole clean.

Bend the cutting development diagram of the inner layer of the front cover (Figure 10.6-3) by 90 degrees along the dotted line, make it into a square cylinder, and attach the joint (the tongue is attached to the inside of the square cylinder). Then, fold the trapezoidal tongue at the notch end into a paper frame, align the notch with the reinforcing frame (Figure 10.6-4) and stick them together. Cut a paper frame with cardboard according to the size of the reinforced frame, align the gap and stick it on the reinforced frame, and stick this paper frame with the square tube outside with adhesive tape, so that a paper slot is formed between the reinforced frame and the rigid paper frame, and the negative can be loaded or taken out from the notched side. This gap is designed to facilitate the loading and unloading of negatives. After the inner layer is finished, the outer layer should be glued, that is, each trapezoid uvula at the other end of the square tube should be bent 90 degrees along the dotted line, coated with glue, aligned with the gap, and inserted into the outer layer. At the same time, a piece of toilet paper should be inserted between the inner and outer layers of each face to ensure that the gap between the inner and outer layers of each face is the same. After the front end of the inner layer is bonded to the surface of the outer layer with circular holes, the inserted toilet paper is pulled out, and the front cover is completed.

As for the manufacture of the back cover, except that the side width is 80+26 mm and there is no hole in the bottom surface, everything else is the same as the outer layer of the front cover. You can refer to the development diagram and corresponding dimensions of the outer layer of the front cover to make it.

Application mode

1. The pinhole camera has a fixed image distance of about 64 mm and a fixed aperture of 0.4 mm, so the aperture is also fixed. Experiments show that the pore size is about 160. When the brightness of the subject is different, it can only be adjusted by exposure time. Because the aperture number of a general camera is about 22, it is impossible to find out the exposure time of aperture 160, so it can be determined according to the ratio of exposure time equal to the square of aperture ratio (that is, t 1: t2 = (f 1: f2) 2). For example, when shooting a scene, the exposure time of aperture 16 is 1/30 seconds, then the exposure time of pinhole camera aperture 160 should be 3.3 seconds. The best exposure time should also be determined by experiments.

2. When taking photos with a pinhole camera, the framing method is shown in Figure 10.6-5. Stick one eye at the midpoint of one side and look out at the opposite ends. Then, the part sandwiched at this angle is the range to be taken. Moving the distance between the camera and the scene can change the image size.

3. Exposure: Take a good picture, calculate the exposure time, open the cardboard covering the small hole and close it until the scheduled exposure time.

4. Film loading and unloading: a single 60×60 mm 2 film is often difficult to buy, so it needs to be cut with a large film. Film loading, unloading and film cutting should be carried out in a dark room without light.

Matters needing attention

1. Be careful not to leak light when making.

2. Pinholes should be round and smooth.

3. Due to the long exposure time, it is advisable to shoot still life.