Tuesday, October 20, 2009
Photography is so ordinary now-a-days that we find it hard to imagine how our forefathers, even in the past century, got along without it. In olden days British prison officers took a person's likeness in form of portraits. They have to wait for a long time for their portrait to get completed. Here is a conversation, “sit for your portrait, sir,’ said stout turnkey of prison. ”Mr. pick complied with the invitation, and sat himself down, when Mr. Weller, who stationed himself at the back of the chair, whispered that the sitting was merely another term for undergoing an inspection by the different turnkeys, in order they might know prisoners from visitors". "Well the artist will come soon” said Mr. Pick. The likeness has been taken in form of portraits and was completed and Mr. Pick was informed that he might now proceed into prison. Still earlier it was a list of "features" that did for such memorized "portraits". It was taken as short stature, and broad chest; one arm shorter than the other; the eyes are blue and hair ginger; a wart on one cheek and another on the forehead. Today we needn't do that; we simply provide a photograph instead.
Monday, October 19, 2009
Photograph was introduced in Russia, first as daguerreotypes-prints on metal plates that were called so after their inventor, Daguerre. It was a very inconvenient method; one has to pose for quite a long stretch- some twenty minutes or so. Some say even they have to sit for 40 minutes before the camera to get just one daguerreotype, from which, moreover, no prints could be made. still the chance to have one's portrait made without the artist's intervention seemed such a wonderful novelty that it took the general public quite a time to get used to the idea. Many still cannot believe that the daguerreotype acts by itself. The photographer begged one gentleman, who came to have his portrait to be seated, adjusted the lenses, inserted the plate, glanced at his watch and retired. While the photographer was present, the gentleman sat as if rooted to the spot. But he had barely gone out when the gentleman thought it no longer necessary to sit still; he rose, took a pinch of snuff, examined the camera from every side, put his eye to the lens, shook his head, mumbled. The photographer returned stopped short in surprise at the doorway, asked the gentleman why did you got up, you should have sat still. But the gentleman didn't accept the fact.
Sunday, October 18, 2009
The camera is based on the same optical principle as our eye. Everything projected onto its ground-glass depends on the distance between the lens and the object. The camera gives a perspective, which we would get with one eye. Now replace our eye to the lens. So, if you want to obtain from a photograph the same visual impression that the photographed object produced, we must, firstly, look at the photograph with one eye only, and, secondly, hold it at the proper distance away. When you look at a photograph with both eyes the picture you get is flat and not three-dimensional. This is the fault of our own vision. When we look at something solid the image it causes on the retina of either eye is not the same. Our brain blends the two different images into one; this is the basic principle of the stereoscope. On the other hand, if we are looking at something that flat-a wall, for instance-both eyes get an identical sensory picture telling our brain that the object we are looking at is really flat. Now you should realize the mistake we make when we look at a photograph with both eyes. In this manner we compel ourselves to believe that the picture we have before us is flat. When we look with both eyes at a photograph which is really untended only for one eye, we prevent ourselves from seeing the picture that the photograph really shows, and thus destroy the illusion which the camera produces with such perfection.
Saturday, October 17, 2009
Holding the photograph at the proper distance away from the eye is very important, or otherwise we get the wrong perspective. How far away should we hold a photograph? To recreate the proper picture we must look at the photograph from the same angle of vision from which the camera lens reproduced the image on the ground glass screen, or in the same way as the object being photographed. Consequently, we must hold the photograph at a distance from the eye that would be as many times less than the distance between the object and the lens as the size of the image on the photograph is less than its actual size. In other words, we must hold the photograph at a distance which is roughly the same as the focal length of the camera lens. A photograph tacked on a wall also seems flat because it is looked at from a still greater distance away. Only the short-sighted with their short focal length of vision, as well as people, who are able to accommodate their vision to see objects very close up, will be able to admire the effect that an ordinary photograph produces when we look at it properly with one eye, because when they hold a photograph 12-15 cm away, they get not a flat image but one in relief the kind of image a stereoscope produces.
Friday, October 16, 2009
Photograph can be enlarged so that people with normal eyesight are able to see them properly, without magnifying glass. It can be done, merely by using cameras having lenses with a long focal length. You already know that a photograph obtained with the aid of a lens having a focal distance of 25-30 cm will appear in relief when viewed with one eye from the usual distance away. One can obtain photographs that won’t seem flat even when looked at with both eyes from quite a distance. You already know that our brain blends two identical retinal images into one flat picture. However, the greater the distance from the object, the less the aid of a lens having a focal distance of 70 cm can be looked at with both eyes without losing the sense of depth. Since it is incommoding to resort to such lenses, let me suggest another method, which is to enlarge the picture you take with any ordinary camera. This increases the distance at which you should look at photographs to get the proper effect. A four fold enlargement of a photograph taken with a 15 cm lens is already quite enough to obtain the desired effect. Cinema goers have most likely noticed that some films seem to spring into unusually clear relief to such an extent at times that one seems to see real scenery and real actors.
Thursday, October 15, 2009
Reproductions in books and magazines naturally have the same properties as the original photographs from which they were made; they also spring into relief when looked at with one eye from the proper distance. But since different photographs are taken by cameras having lenses with different focal lengths, one can find the proper distance only by trial and error. Cup one eye with your hand and hold the illustration at arm’s length. Its plane must be perpendicular to the line of vision and your open eye must be right opposite the middle of the picture. Gradually bring the picture closer, steadily looking at it meanwhile; you easily catch the moment when it appears in clearest relief. Many illustrations that seem blurred and flat when you look at them in your habitual way acquire depth and clearness when viewed as I suggest. One will even catch the sparkle of water and other and other such purely stereoscopic effects. It’s amazing that few people know these simple things though they were all explained in popular science books more than half a century ago. There is one more thing we must note. Photographic enlargements, as we have seen, are more life like; photographs of a reduced size are not. True, the smaller size photograph gives a better contrast; but it is flat and fails to give the effect of depth and relief. You should now be able to say why: it also reduces the corresponding perspective, which is usually too little as it is
Wednesday, October 14, 2009
While we see solid objects we see it as a three dimensional one. For several reasons, firstly, the different lighting of the different parts of objects enables us to perceive their shape. Secondly the strain we feel when accommodating our eye to get a clear perception of the object’s different parts that are at different distances from the eye also plays a role; this is not a flat picture in which all the parts of the object depicted are set at the same distance away. And thirdly, the most important cause is that the two retinal images are different, which is easy enough to demonstrate by looking at some close object, shutting alternately the right and left eye. Imagine now two drawings of one and the same object, one as seen by the left eye, and the other, as seen by the right eye. If we look at them so that each eye sees only its own drawing, we get instead of two separate flat pictures one in relief. The impression of relief is greater even than the impression produced when we look at a solid object with one eye only. As you see the stereoscope’s basic principle is extremely simple: all the more amazing, therefore, is the effect produced. I suppose most of you have seen various stereoscopic pictures. Some may have used the stereoscope to learn stereometry more easily. However, I shall proceed to tell you about applications of the stereoscope which I presume many of you do not know.
Tuesday, October 13, 2009
Suppose you have two absolutely identical drawings, of two equal black squares, for instance. In the stereoscope they appear as one square which is exactly like either of the twin squares. If there is a white dot in the middle of each square, it is bound to show up on the square in the stereoscope. But if you shift the dot on one of the squares slightly off centre, the stereoscope will show one dot, however, it will appear either in front of, or beyond, the square, not on it. The slightest of differences already produces the impression of depth in the stereoscope. This provides a simple method for revealing forgeries. You need only put the suspected bank-bill next to a genuine one in a stereoscope, to detect the forged one, however cunningly made. The slightest discrepancy, even in one teeny-weeny line, will strike the eye at once appearing either in front of, or behind, the banknote. When an object is very far away, more than 450 meters distant, the stereoscopic impression is no longer perceptible. After all, the six centimeters at which our eyes are set apart are nothing compared with such a distance as 450 meters. No wonder buildings, mountains, and landscapes that are far away seen flat. So do the celestial objects all appear to be at the same distance, though, actually, the moon is much closer than the planets, while the planets, in turn, are very much closer than the fixed stars. Naturally, a stereoscopic pair thus photographed will not produce the illusion of relief in the stereoscope
Monday, October 12, 2009
If we direct our tele-stereoscope at the moon or any other celestial object, we shall fail to obtain any illusion of relief at all. This is only natural, as celestial distances are too big even for such instruments. After all, the 30- 50 cm distance between the two lenses nothing compared with the distance from the earth to the planets. Even if the two telescopes were mounted tens and hundreds of kilometers apart, we would get no results, as the planets are tens of millions of kilometers away. This is where stereoscopic photography steps in. suppose we photograph a planet today and take another photograph of it tomorrow. Both photographs taken from the same point on the globe, but from different points in the solar system, as in the space of 24 hours the earth will have traveled million of kilometers in orbit. Hence, the two photographs will not be identical. In the stereoscope, the pair will produce the illusion of relief. As you see, it is the earth’s orbital motion that enables us to obtain stereoscopic photographs of celestial objects. Imagine a giant with a head so huge that its intraocular distance ranges into millions of kilometers; this will give you a notion of the unusual effect astronomers achieve by such stereoscopic photography.
Sunday, October 11, 2009
Science cannot give you or me a third eye, but it can give us the magic power to see an object as it would appear to a three- eyed creature. Let me note first that a one- eyed man can get from stereoscopic photographs that impression of relief, which he cannot and does not get in ordinary life. For this purpose, we must project onto a screen in rapid sequence the photographs intended for right and left eyes that a normal person see with both eyes simultaneously. The net result is the same because a rapid sequence of visual images fuses into one image just as two images seen simultaneously do. (It is quite likely that the surprising “depth” of movie films at times, in addition to the causes mentioned, is due also to this. If the movie camera sways with an even motion, as often happens because of the film- winder, the stills will not be identical and, as they rapidly flit onto the screen, they will appear to us as one three- dimensional image). In that case, a two- eyed person simultaneously watches a rapid sequence of two photographs with one eye and a third photograph, taken from another angle. One eye would get a single image, but in relief, from a rapidly alternating stereoscopic pair, while the other eye would look at the third photograph. This “three - eyed” vision enhances the relief to the extreme.