Manual of Photography

Front Cover
U.S. Government Printing Office, 1896 - Photography - 112 pages
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Page 102 - A FEW REMEDIES AGAINST BLISTERING OF ALBUMEN PAPER. Do not dry the paper by excessive heat. Avoid acidity in solutions. Moisten the print before washing with a sponge saturated in alcohol. Immerse the print before fixing in a weak alum. Add a trace of aqua ammonia to the fixing bath. Add one-tenth part of alcohol to the ordinary toning bath.
Page 19 - R', which is the focus for all rays coming from R. The point R' is said to be the image of the object R, and when the two points are considered together they are called conjugate foci. If the incident beam is composed of parallel homogeneous light, the rays will all be brought to a focus at a point on the principal axis, called the principal focus of the lens, and the distance of this point from the optical center is the principal focal length, which is always a fixed quantity for any given lens....
Page 17 - ... (6) piano convex; (c) double concave; (d) piano concave; (e) converging, and (/) diverging meniscus. Those lenses which are thicker at the center than at the edges are converging or concentrating lenses, and those which are thicker at the edges than the center are diverging. FOCUS OPTICAL CENTER. The focus of a lens is the point where the refracted rays or their prolongation meet; if the rays themselves intersect after refraction the focus is real, and if their prolongations meet the focus is...
Page 48 - Mix in the order given / use cold. After exposure, soak the paper in water until limp ; then immerse in the developer. The image should appear slowly, and should develop up STRONG, CLEAR and BRILLIANT. When the shadows are sufficiently black, pour off the developer and flood the print with the CLEARING SOLUTION. Acetic Acid I dram.
Page 111 - To renew the charge, book must be brought to the desk. TWO WEEK BOOK DO NOT RETURN BOOKS ON SUNDAY DATE DUE Form 7079 3-5O 2OM S UNIVERSITY OF MICHIGAN...
Page 20 - ... the focus B', and thus obtain the image A' B', which is inverted and smaller than the object AB. The relative size of the image and object will be directly as the conjugate foci, and these can be found at once from the equation of the lens. SPHERICAL ABERRATION. If, however, we consider the form of the lens, we will find that all the rays emerging from one point on the object are not brought to the same focus, because the rays incident on the edges of the lens are refracted to a greater extent...
Page 19 - ... the image and object, respectively, from the optical center and /the focal length, from which we see that for all positions of the object from an infinite distance away from the lens to double the principal focal distance, the image will be on the other side, between a distance equal to the principal focal length and double this length. These are the limits of the image and object in the ordinary cases. If we place this expression in the following form : i = —,, and suppose the object to...
Page 17 - Double convex; (6) piano convex; (c) double concave; (d) piano concave; (e) converging, and (/) diverging meniscus. Those lenses which are thicker at the center than at the edges are converging or concentrating lenses, and those which are thicker at the edges than the center are diverging. FOCUS OPTICAL CENTER. The focus of a lens is the point where the refracted rays or their prolongation meet; if the rays themselves intersect after refraction the focus is real, and if their prolongations meet the...
Page 18 - D' and E by a straight line. The point O will be the optical center of the lens. Let us take a point R, on the principal axis as a source of light; the ray RD passes through the optical center and is not deviated. The ray RK on striking will be refracted in the direction KG toward the perpendicular to the surface KD in accordance with the law of refraction, as glass is denser than air. On emerging at G it is refracted away from the perpendicular to the surface CG, since it passes from a denser to...
Page 18 - ... of curvature of the two surfaces of a lens is called the principal axis and contains a point known as the optical center, which has the property by virtue of which, if a ray passes through it, the ray will not be deviated. The optical center can always be found by drawing two radii parallel to each other, one from each center of the curvature of the surface until the radii intersect their respective surfaces, then draw a line joining these two points. The intersection of this last line with the...

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