Fine Cameras and How They Are Made
Tue, 10/29/2013 - 1:02pm
The Argus C-Four takes center stage in this promotional video for Argus Cameras. The narrator intones, "It takes three things to make a fine camera . . ." and with that launches into a highly technical and detailed description of every step in the camera-manufacturing process at Argus Cameras of Ann Arbor. Scenes of the scientists and craftsmen creating the Argus C-Four are interwoven with scenes of customers using the camera to take family photos and outdoor shots. The easy-to-use, lightweight Argus cameras revolutionized photography, essentially creating "popular photography." Enjoy this pre-Mad Men video, visit AADL's Argus Camera online exhibit and take a walk over to the Argus Museum for even more Argus history. 27:09 min. c.1953
- [00:00:00.00] [MUSIC PLAYING]
- [00:00:27.89] SPEAKER 1: It takes three things to make a fine camera. It takes a fine lens, an accurate range finder, and a precision shutter. This prize-winning photograph is an enlargement from a tiny image on 35 millimeter film.
- [00:00:45.84] A fine camera took this picture. Its flawless lens produces pictures that have tone quality, harsh highlights, no blocked up shadows. 35 millimeter camera should fit the hand nicely, be easy to focus quickly and accurately. They should have beauty, should instill pride of ownership.
- [00:01:13.44] The creation of fine cameras, as with all precision instruments, depends on thorough scientific research and talent, and on skilled craftsmanship. In this modern plant that Ann Arbor, Michigan, scientists, designers, engineers, and craftsmen all team together to produce a line of cameras that dollar for dollar are superior to any made anywhere in the world. The three most important features of this fine camera are an exceptional lens, ranking among the best that lens makers know how to produce, an extremely accurate shutter, and the most precise lens coupled focusing range finder.
- [00:02:04.59] Let's take up these features, one by one, beginning with the lens. The formula for a good camera lens requires a vast number of calculations to determine exactly the right radius of curvature for each surface and to suit the refractive index of the glass. A lens of good design is corrected for chromatic aberration, so that all colors of the spectrum will focus to the same point. A lens having insufficient color correction will bring each color to a different focus. Fully color corrected lenses give you color slides of exceptional definition, color slides that project crisp and clear and are sharp over all of the screen.
- [00:03:06.40] A poor camera lens may produce an image sharp only in the center, and out of focus in the corners and [INAUDIBLE]. A good camera lens produces an image sharp all over and having no distortion. This critically sharp and fully correct-- blanks of glass-- ordinary glass, but a special kind, called optical glass.
- [00:03:33.12] The test sample is ground and polished on one side and one edge, and sent to the laboratory, where it is tested for its refractive index, that is whether it bends rays of light exactly as specified. If the test sample shows that the glass in the batch is up to specifications, the blanks are ready for the lens-making operations. The first step is to spray a dark coating on one surface of each blank. Then the blanks are mounted in a special fixture known as a blocking tool.
- [00:04:10.51] Before the blanks are mounted, the blocking tool is heated in an electric induction heater. This is one of the very few lends blocking installations in the country employing the extremely modern induction heating method. Pitch is applied to the hot tool. Formally, pitch was heated in open pots and applied by hand. The resulting gas and fumes, and the many painful burns to workers, made the old method very inefficient. Production was about 1/3 less than by the method you are watching now.
- [00:04:44.66] The blocking tool then goes to a cooling bath, where the pitch hardens, thus assuring that the blanks are held securely. This particular type of blocking tool is suitable for grinding only one curved surface of the lens. The lens elements vary in size, and each has surfaces of different curvatures. Here are just a few of the many different sizes and shapes of blocking tools needed for grinding and finishing camera lenses.
- [00:05:19.41] The making of blocking tools, such as these, is only one of the many special operations involved in tooling up for lens and camera manufacturer. And one of the most important departments in this modern plant is where the special tools, dyes, and fixtures are made. These blocking tools are a very special kind, with recesses machined in the surfaces to receive the lens blanks.
- [00:05:50.14] Now, let's follow the lens blanks we saw a moment ago to the grinding room, where the lenses are put in the chuck of a precision grinder. Modern methods have replaced the old slow hand operations in lens grinding. This first grinding is called generating the spherical surface. It is done with a hemispherical wheel containing coarse diamond grit.
- [00:06:21.25] After the removal of rough stock with of coarse wheel, there follows another grinding with a wheel containing fine diamond grit. This is one of the few diamond grind installations in America. In this fine grind operation, the lens blanks are brought in a few seconds within tolerances, which formerly required several hours of painstaking hand grinding to achieve.
- [00:06:51.62] After still another and much finer grinding, the lenses are thoroughly cleaned. The surfaces have a smooth velvety appearance, and the radius of their curvature is accurate within 1/100,000 park of an inch. Now the time consuming polishing begins.
- [00:07:18.83] The lenses are still held on the same blocking tool, and polished on a lap of pitch. A mixture of water and the rare earth cerium oxide gives an extremely high polish. It requires craftsmanship of the highest order to assure that polishing reaches its ultimate perfection. Periodically throughout the polishing operations, the lenses are cleaned in preparation for testing the accuracy of the lens curve, using one of the most precise testing devices known, the optical test plate.
- [00:08:03.92] This [INAUDIBLE] ground and polished to the exact right-- these are like the contour lines on a map and enable the lens maker to know whether the lens meets rigid specification. The number and width of these Newton rings indicate the progress being made in the critical polishing process. Lenses that show many rings or decentered rings are not acceptable until they've past the Newton rings test.
- [00:08:39.56] But they must also pass close inspection for scratches and pits. After the lenses have passed inspection, and a protective coating has been sprayed over the polished services, they are removed from the block and remounted on another tool, whose radius of curvature differs from the first one used, because the curvature on one surface of each lens element is different from that of the other service.
- [00:09:09.55] Now, a brief look at the photographic lens, whose beginnings have been taking shape. In a lens system of this type, there are six surfaces to be ground and polished, and all but the two outside surfaces have a different radius of curvature. Hence, five different blocking tools are needed, each having its particular radius of curvature.
- [00:09:35.79] The coarse and medium grindings require 10 different wheels, two for each radius. And the final grinding requires five more, 15 in all. Then five different polishing heads are required. And finally, five different quartz test plates to check the accuracy of the various curves. Here is one of the finished lenses ground, polished, tested, and having a radius of curvature accurate to a few millionths of an inch.
- [00:10:11.19] Every lens must be centered so that its optical axis passes exactly through its mechanical center. At first, the small red cross reflected from its service oscillates. The operator expertly brings the lens into center alignment, until the cross remain stationary-- proof that the lens is accurately centered. Then a squeeze of cold water from the operator sponge sets the pitch firmly, holding the lens so that the edge may be accurately ground with relation to the established optical center.
- [00:10:58.43] The edges are ground so that the mechanical center of the lens is precisely centered with the optical axis. This is essential to the formation of good images. After centering, the lenses are washed and carefully dried. The lenses are given a beauty inspection for bubbles or surface scratches, chipped edges, and other imperfections. Even with the most precise methods, an occasional reject shows up, is immediately spotted, and marked in red to prevent its traveling further in the production process.
- [00:11:37.94] The next operation is the coating of the lenses to assure the finest performance. The lenses are placed in a large holder. A charge of magnesium fluoride is placed in the lens coating machine on an electric heating unit. Then the lenses go in.
- [00:12:15.14] After the cover is lowered, the air is pumped out to obtain the vacuum necessary for high-quality coating. The magnesium chloride is vaporized by the electric heater and deposits uniformly on the surface of the lenses. What happens inside the glass bell is depicted here by animation.
- [00:12:36.95] With the atmosphere exhausted of all foreign particles, the magnesium chloride vaporizes in the electric crucible. And the tiny molecules travel in straight lines to the lens surfaces. Critical control enables the operators to obtain a thickness of coating equal to 1/4 of one wavelengths of light, or about 1/5,000,000 of an inch. Should the coating exceed this thickness or fall short of it, there is a considerable drop in lens performance. Hence, great care is exercised in this phase of producing a fine lens.
- [00:13:24.52] After the bottom surfaces of the lenses have received their coating, they are removed from the machine. The lenses are then reversed for coating the other side. Among the qualities imparted to a lens by coating is to increase its speed by permitting more light to pass through.
- [00:13:47.62] Here, light is shown passing through an uncoated lens. See how bright the incoming light is, and how much dimmer the outgoing light. With coated lenses, the light that comes out has virtually the same intensity as the light that goes in. And coating a lens reduces flare, lets you shoot into the light.
- [00:14:13.47] An uncoated lens produces picture-spoiling flare. Besides improving the quality of pictures, especially color transparencies, lens coating helps eliminate flare or ghost images, such as you see here. A coated lens gives you this.
- [00:14:34.20] Lens elements, no matter how fine and accurate each one is, perform well only if they are mounted properly. Any decentering or misalignment of the elements in mounting, ruin the picture-making qualities of the lens. So the fine photographic lens needs not only extremely skillful craftsmanship in making the individual elements, but also the same high standards of craftsmanship in making the lens--
- [00:15:16.01] The lens elements and mounts are assembled by nimble fingers. Then comes the test for sharpness and focus adjustment. And to make sure that the lenses meet the established standards, they are carefully checked in the laboratory. Here on the optical bench, the lenses are tested for focal length, stigmatism, flatness of field, sharpness, color correction, coma, distortion, and a host of other things.
- [00:15:57.56] A fine lens is a jeweled embodiment of all the skill and care that has gone into its design and making. Just as important as a fine lens, which speaks the truth in the picture it makes, is a shutter, which speaks only the truth, when it makes the exposures. Camera owners like to be certain that the shutter speed is exactly what the setting indicated.
- [00:16:25.93] As you know, there are three principal types of shutters-- the between the lens, the behind the lens, and the focal-plane shutter. This camera is typical of those equipped with a between-the-lens shutter. These cameras have behind-the-lens shutters, whose mechanism is contained within the camera body itself. This behind-the-lens shutter, like a fine watch, typifies the highest degree of performance, accuracy, and dependability. The precision, which has been built into this shutter, is the finest that machining skill can produce.
- [00:17:09.73] The metal of which the parts are made must pass many tests for hardness, springiness, and other necessary qualities. Light, flexible Swedish steel is stamped into shutter leafs. Then skilled hands begin the assembly of the many parts of the shutter.
- [00:17:53.91] The shutter assembly goes on to the front plate. Then the objective lens. A most important operation is setting the shutter. The front plate and objective lens go into the frame. Then the lens mount barrel is installed.
- [00:18:57.64] The flash synchronizer is checked. The camera is nearing completion, as the range finder is installed. The range finder is carefully adjusted and checked for accuracy. Then the focusing barrel and diaphragm rings are attached.
- [00:19:58.17] The focusing scale is very carefully adjusted and set firmly in place. After the focusing scale has been set, the shutter must pass a final series of tests, a checking at every speed setting. This electronic equipment maintains ceaseless control on shutter accuracy and synchronizer performance. After assembly has been completed, all cameras are carefully inspected. The final step-- the camera receives its attractive durable covering.
- [00:20:53.81] Quality control is exercised in every single manufacturing step. The laboratory conducts continuing tests on shutters and lenses. This oscilloscope, like a miniature TV screen, affords a visual picture of shutter and synchronizer performance. In addition, it records it photographically for further study.
- [00:21:29.29] Here's a black and white oscilloscopic trace. The lower image, composed of tiny dots, each representing a predetermined fraction of a second, shows exactly how long it takes the camera shutter to open, how long the shuttle remains open, and how quickly it closes at the end of the exposure. The [INAUDIBLE] shows the flash duration with relation to shutter position. Good accurate synchronization produces a tracing like this, showing that the flash is occurring neither too early, nor too late to be fully utilized.
- [00:22:08.69] Next in importance to lens and shutter, is a finder that's easy to use. This camera has a brilliant reflex finder, enabling you to see clearly the picture you're going to get. This is a beginner's camera with fixed focus lens. Makes good pictures of subject 7.5 feet away and farther. Another type of camera with reflex finder provides for focusing, from the most distant subjects to those very close up.
- [00:22:46.52] Lens-coupled range finder focusing is the most convenient means ever device and the most accurate. Before focusing, the eye sees a double image within the circle. As the focusing knob is turned, one image moves until it merges with the other. Now the lenses is in focus.
- [00:23:10.73] The range finder is accurate over the entire focusing range. That has been assured by [INAUDIBLE] during assembly. With this combined-- range and viewfinder, you can even wear glasses and still get a large clear image. Precision in a range finder is essential, especially when shooting wide open. --camera having a built-in flash synchronizer adds to picture-making pleasure, particularly, if it's easy to plug in, and you have no dangling wires to insert. And if it has an easy injector to prevent burnt fingers.
- [00:24:05.06] Here's a well-known 35-millimeter camera with built-in flash synchronizer are and a plug-in flash unit. And here's America's most distinguished 35-millimeter camera getting ready for flash photography. This fine camera has a built-in flash timer, as well as built-in synchronizer to take care of all commonly used flash lamps.
- [00:24:36.84] And here is the convenient built-in delay switch, set at F, the fast or gas-filled bulbs with their 5-millisecond delay, are accurately synchronized. Set at M, or medium, the slower 20-millisecond delay bulbs function accurately. The convenient flash gun has a removable adapter, so you may easily use any flash bulb at any shutter speed in this camera. You can use any of these lamps with the shutter speed specified for each for perfectly exposed flash pictures in black and white or color. The film wind on this camera, in addition to winding the film for the next exposure, also winds the shutter and sets the exposure counter.
- [00:25:42.90] The real pleasure of owning and using a fine camera depends on the lens, the shutter, and the focusing mechanism. A lens, accurately ground and polished, coated, color corrected, and in a precise mounting. A finder that gives large, clear images combined with precise-coupled range-finder focusing. And a sturdy rugged shutter, built to the highest standards of accuracy and precision. And the reward for using a fine camera is the real pleasure and enjoyment its pictures provide.
- [00:26:22.46] [MUSIC PLAYING]