Optical character recognition

“ If a person gifted with the visualizing power in perfection should pose his eye in the place of the object-glass of the camera, would the generic image in his brain be identical with the photographic composite? (I am assuming, for argument's sake, that the photograph gives a true rendering of any optical image, which, in strictness, it does not.) ”

“ It is not always understood that the so-called magnifying power of a lens applied to the eye, as in a microscope, is derived from [Pg 4] its enabling the eye to approach more nearly to its object than would otherwise be compatible with distinct vision. The common occurrence of walking across the street to read a bill is in fact magnifying the bill by approach; and the observer, at every step he takes, makes a change in the optical arrangement of his eye, to adapt it to the lessening distance between himself and the object of his inquiry. ”

“ In the case of the illiterate man the perception of the optical properties is the total effect. But the literate man has something in his consciousness already, and this something combines, as it were, with the optical perception, and makes him aware of certain secondary properties of the printed characters. ”

“ For the world of external objects is a whole, and so is its image appearing in the camera. Equally, the light entering the camera is not a sum of single rays. Pure observation leads to the following description of the optical process.
By surveying the path which the light takes from the illuminated surface of the outer objects via the pin-hole to the optical image inside the camera, we realize that the light-realm engaged in this process has the shape of a double cone, with its apex in the opening of the camera. ”

“ Years ago, there was a little instrument of a similar kind, sold for a penny in the streets of London, which consisted of a morsel of looking-glass set at an angle, in a pill-box, and which gave the possessor the power of seeing all that was going on behind him. Persons who wear dark preservers are often in the habit of observing all that is going on behind their backs by the reflection seen in the corner of their glasses.
Such are the principal optical recreations founded on the reflecting and refracting properties of mirrors and lenses. ”

“ By inspecting a dead carcass we shall never discover the principle of life; by inspecting a dead eye, or a camera obscura, we shall never discover the principle of vision. Yet, though there is no seeing in a dead eye, or in a camera obscura, optics deal exclusively with such inanimate materials; and hence the student who studies them will do well to remember, that optics are the science of vision, with the "fact" of vision left entirely out of the consideration. ”

“ IT BEATS OPTICAL WORK OUT OF SIGHT. In optical work, as in refined drawing, the hand goes beyond the eye, and one has to depend upon the feel; and when one has once learned what a delicate affair touch is, one gets a horror of all coarse work, and is ready to forgive any amount of feebleness, sooner than that boldness which is akin to impudence. In optics the distinction is easily seen when the work is put to trial; but here too, as in drawing, it requires an educated eye to tell the difference when the work is only moderately bad ”

“ Of all the senses none is more frequently the seat of such deceptive judgments than that of sight; and in the science of physiological optics a very considerable share of attention is claimed by optical illusions. For the purposes of convenience, we may draw a distinction between these illusions, which are the direct result of certain properties or imperfections of the eye as an optical instrument, and those which arise from obliquities of judgment in interpreting the sensations optically impressed upon the retina of the eye. ”

“ The next care to be taken, in respect of the Senses, is a supplying of their infirmities with Instruments, and, as it were, the adding of artificial Organs to the natural; this in one of them has been of late years accomplisht with prodigious benefit to all sorts of useful knowledge, by the invention of Optical Glasses. By the means of Telescopes, there is nothing so far distant but may be represented to our view; and by the help of Microscopes, there is nothing so small, as to escape our inquiry; hence there is a new visible World discovered to the understanding. ”

“ The cause of colour-blindness is completely unknown; philosophers and physiologists are still in the realms of hypothesis concerning this peculiar optical defect. As yet, the most careful observation has failed to detect any difference between the eyes of those who are colour-blind, and the eyes of ordinary persons, that could in any way account for this singular affection of the sense of sight. ”

“ The most important optical instrument with which we have to deal is the projecting arc lamp and its optical system. The passage of light through this system of lenses is altogether different from that passing through a camera lens for instance. In a camera lens the picture is formed upon the ground glass screen by the light reflected from the object. From any single point of the object, rays of light strike all parts of the lens, pass through it, and are recombined or focused at some point behind it. ”

“ It was at one time the fashion to copy the images formed in the kaleidoscope as patterns for room papers, muslins, curtains, shawls, and other similar fabrics, but thanks to the spread of artistic taste in this country the decorative designer now relies more on his own talent than any aid he may receive from optical instruments. ”

“ For some purposes, as for instance in becoming acquainted with the general character of the spectrum, a feebler light, such as gaslight, or light from electrical glow lamps, may be employed, since the spectrum may be viewed directly by the eye without the intervention of a screen. They have two drawbacks for our object: one being the want of general intensity, and the other the feeble luminosity of blue and violet rays in their spectrum (see page 110) . The limelight we can also dismiss for want of steadiness. ”

“ Artists will be interested in the abstracts of five lectures "On the Relation of Optics to Painting," which were delivered in Cologne, Berlin, and Bonn. After the introductory he takes up successively the subjects, form, shade, color, and harmony of color. His point of view is neither that of the practical artist nor of the student of pictures and schools of painting, but it is that of the physiological optician who is master of a subject. He shows in various ways how a knowledge of the mode of perception of the organ of vision may be of importance to the artist. ”

“ The peculiar appearances known as spectres in optics are certain illusions of vision in which an object is apparently presented to the view which does not really exist. In such cases either the brain, the retina, or the optic nerve are unnaturally excited, and made sensitive to an appearance that, physically speaking, does not exist. There is such a close connexion between the senses and the mind, that we continually, and without knowing it, transfer to the physical world that which belongs to the domain of thought. ”

“ If we look into another person's eye we may see there a picture of the whole field of his vision reflected from his lens. It is true that what we see is not what he sees, for that is on his retina, but the analogy of this with a photographic camera, where we see the picture on the ground glass, seems obvious and natural; and so we think of knowledge, so far as it depends on the sense of vision, as consisting in more or less vivid, more or less faded, copies of real things stored up by the memory. ”

“ If we take, for the sake of simplicity, not a picture, but a scale with four or five-tone gradations from light to deep black, the light tones will act more or less on the sensitive photographic plate according to their degree of brightness, but as the rays of light have to pass through the cross-lined screen interposed between the lens and sensitive plate, and as the rays can only pass through the transparent parts and not through the opaque, no homogeneous surface is obtained on the negative, but a tone produced by the cross-lines of the screen. ”

“ An artist who views color subjectively and is rarely familiar with the spectral basis may match a green leaf perfectly with a mixture of pigments. A photographic plate, a visual filter, or a spectroscope will reveal a difference which the unaided eye does not.
Some time before the Great War began, it occurred to the writer that colored filters could be utilized in aiding vision by increasing the contrast of the object to be viewed against its surroundings. [9] Studies were made of various filters, made with the object of the experiment in mind, in viewing the uniforms of various armies. ”

“ Other artists, both in portrait and in landscape, now avail themselves of photography, both as an auxiliary and a guide in their profession; but there are certain difficulties and imperfections in the art itself, and so many precautions required in its right application, whether we use its pictures single, as representations on a plane, or take them binocularly, to be raised into relief by the stereoscope, that we must draw from the principles of optics the only rules which can be of real services to the arts of design. ”

“ If two cameras are out of focus to the same degree, they will take two imperfect pictures exactly alike. If two eyes are out of focus to the same degree, similar impressions will be made upon the retina of each; but the impressions made upon the mind may be totally unlike, whether the eyes belong to the same person or to different persons. If the normal eye looks at an object through glasses that change its refraction, the greyness and blurring produced are uniform and constant ”

“ The object then forms an image in the interior of the eye, though small, just as a picture is represented on the table of the camera.
The optician's business is to make an instrument which is analogous to the mere mechanism of the eye, and he is well able to explain the mode by which objects arrive on the retina; but who can say how they communicate with the brain, and become a part of man's knowledge? ”

“ Doubtless the future will see the production of efficient light of many qualities or colors, but to-day many of the demands must be met by modifying the artificial illuminants which are available. Vision is accomplished entirely by the distinction of brightness and color. An image of any scene or any object is focused upon the retina as a miniature map in light, shade, and color. Although the distinction of brightness is a more important function in vision than the ability to distinguish colors, color-vision is far more important in daily life than is ordinarily appreciated. ”

“ Work built up on outline drawing to which has been added light and shade, colour, aerial perspective, &c., may eventually approximate to the perfect visual appearance. And inversely, representations approached from the point of view of pure vision, the mosaic of colour on the retina, if pushed far enough, may satisfy the mental perception of form with its touch associations. And of course the two points of view are intimately connected. You cannot put an accurate outline round an object without observing the shape it occupies in the field of vision. ”

“ Chalmers seated among his friends on the Moderator’s chair––we find an exemplification sufficiently striking of the laws on which this seemingly mysterious power depends. They are purely structural laws, and relate not to the mind, but to the eye,––not to the province of the metaphysician, but to that of the professor of optics. The lens of the camera obscura transmits the figures to the prepared paper, on quite the same principle on which in vision the crystalline lens conveys them to the retina. ”

“ The opposite illustration shows the most perfect camera obscura that can be imagined, namely, the human eye. Here we have a dark chamber, a double convex lens, and an image falling upon the back. Here the optic nerve comes into play, takes cognisance of the image, and conveys the idea to the{281} brain. With a little trouble, a real eye, say that of an ox, can be dissected out, and employed as a camera obscura, the operator seeing in the back of the eye, or “retina,” the same image which the ox would have seen if it had been alive. ”

“ For such investigations new instruments are needed, of unexampled powers and accuracy, some for angular measurements, some for mere power of seeing. Photography comes continually more and more to the front; and the idea sometimes suggests itself that by-and-by the human eye will hardly be trusted any longer for observations of precision, but will be superseded by an honest, unprejudiced, and unimaginative plate and camera. ”

“ If we throw the whole spectrum on the screen, and ask a person with normal vision to point out the brightest part, he will indicate the yellow, whilst a red-blind will say the green, and so on. This tells us that the various types of colour blind must see their spectrum colours with luminosity differing from that of the normal eye. The difference can be measured by causing both to express their sense of the brightness of the different parts of the spectrum in terms of white light, or of one another. Brightness and luminosity are here used synonymously. ”

“ The method which I intend to describe is not quite so simple as some others, but it has great advantages in the way of convenient manipulation, and affords the means of demonstrating a number of interesting colour effects in an easily intelligible manner. By the simple operation of moving aside a lens out of the track of the light, we can gather up and thoroughly mix together all the variously coloured rays of the spectrum and cause them to form upon [Pg 44] the screen a bright circular patch, which, though due to a mixture of a thousand different hues, is absolutely white. ”