NA TURK 



589 



THURSDAY, OCTOBER 18, 1894. 



THE OPTJCS OF PHOTOGRAPHY. 

 Handbuch der Photographie : II Theil : Das Licht im 

 Dienste der Photographie nnd die neueslen Fortschritte 

 der photographischen Opiik: By Prof. Dr. H. W. 

 Vogel. (Berlin : Robert Oppenheim (Gustav Schmidt), 

 1894.) 



THIS second part of Dr. \'ogers well-known hand- 

 book is the fourth edition, completely revised and 

 enlarged, as we are informed on the title-page. With 

 the inde.x it runs to 367 pages, and is embellished with 

 numerous figures and a coloured frontispiece illustrating 

 the Vogel-Kurtz process of printing in three superposed 

 colours. The result is very satisfactory, and the grapes, 

 pineapple, lemon, and other fruit appear very natural. 

 There should be a promising future for this chromo- 

 lithographic development of photography, which, it may 

 perhaps be not altogether unnecessary to state, has 

 nothing to do with the great question of direct photo- 

 graphy in natural colours. 



It is difficult within reasonable compass to give an 

 adequate notion of the wide range of subjects dealt with 

 in the present work. Everything likely to be of use to 

 the scientific and practical photographer is treated of 

 with more or less completeness. While the first part, 

 which we noticed in these columns some years ago 

 ( vol. xliii. p. 3), deals with the chemical aspect of the 

 subject, the instalment under consideration is devoted 

 to the optical aspect, using the term optical in the wide 

 sense of comprising the general nature of light regarded 

 as a chemically active natural force. The optics of 

 photographic leises finds a place in the present part in 

 the form of an appendix covering some ninety odd 

 pages, and copiously illustrated. The appendix covers 

 all that is usually comprised in this country under 

 the term "photographic optics," and it is treated in a 

 manner intended to be generally understandable ; the 

 actual German heading is, " Gemeinverst.'indliohe Dar- 

 stellung der Grundzuge der photographischen Optik." 

 The seven chapters forming the appendix deal with the 

 methods of forming images, lenticular refraction, faults 

 of lenses, intensity of illumination and " field," differences 

 in photographic objectives, the stereoscope, panorama 

 apparatus, and the principles of photographic surveying. 

 The seventh chapter is of especial interest because it 

 deals with the latest advances in the construction of 

 photographic objectives, and comprises, among other 

 things, a description of the teleobjectives of Miethe, .Stein- 

 heil, and Zeiss. The remarkable efficacy of this new 

 addition to the resources of the photographer is shown 

 by two pairs of reproductions of photographs of views 

 taken from the same spot, one with an ordinary, and the 

 other with the teleobjective. 



We have called attention to the appendix first, not 

 because we desire to follow the practice of certain readers 

 of fiction who form an opinion as to whether a book is 

 worth re iding by beginning at the last chapter, but 

 because it treats of that portion of the subject which we 

 here are too apt to regard as comprising the whole of 

 photographic optics. The main portion of the work 

 NO. 1303, VOL. 50] 



under notice treats of subjects quite distinct from that 

 of the properties and construction of lenses, but which 

 are of equal importance in modern photography. This 

 portion of the book consists of thirty-one chapters ex- 

 tending over 266 pages. A brief analysis of the contents 

 will give the reader a general idea of the scope : — 

 Intensity of light and Lambert's law, measurement of 

 intensity, the optical photometer, standards of light, 

 Weber's definitions, the brightness of transmitted and 

 reflected light for different substances, the photographic 

 photometer or sensitometer, photographic standards of 

 light, Miethe and Michalkes law of photographic 

 reciprocity in developed films, dependence of the trans- 

 parency of the negative on the period of exposure and 

 on the intensity of the illumination, the chemical inten- 

 sity of day and sunlight (Bunsen and Roscoe), intensity 

 under limited sky illumination, continuing rays and the 

 effects of previous and subsequent illumination, sources 

 of artificial light for photography, reflection, halation, 

 composition of light and photography of coloured objects, 

 chemical action and absorption, properties of optical 

 sensitisers, action of colouring matters on collodion and 

 gelatine plates, shifting of the maxima of photographic 

 activity (Wiedemann's law), relations between sensitive- 

 ness to light and optical sensitisers of the eosin series, 

 other optical sensitisers, action of simple and mixed 

 optical sensitisers on sensitiveness, ray filters {i.e. colour 

 screens), instruments for the study of the colour sensitive- 

 ness of photographic films {i.e. spectrographs), testing of 

 colouring matters and films for colour sensitiveness, 

 reproduction of natural colours by multiple photography, 

 direct photography in natural colours, colour perception 

 and complementary colours, observations on the colour 

 transparency of the atmosphere. 



To those who are acquainted with photography as a 

 science,' the headings to the various chapters will give 

 sufficient indication of their contents. There are, how- 

 ever, many topics of importance hidden away, as it .were, 

 among the mass of information contained in the book, 

 and to some of these we may direct the attention of the 

 general reader who, without being an expert, may wish 

 to ascertain the present state of knowledge with regard 

 to such subjects as are of physical or chemical interest 

 beyond their immediate application to photography. 

 Thus, with regard to the standards of light we learn that 

 preference is given over all others to the amyl acetate 

 lamp of Hefner-Alteneck— a preference which many in 

 this country will no doubt be prepared to dispute. Then, 

 again, with respect to the amount of light reflected from 

 various surfaces (chapter v.), some useful measurements 

 are given, partly from the author's observations and partly 

 from determinations by Kirschmann. The photographic 

 efficiency of various sources of light (chapter vii.) is also 

 a subject of general interest, apart from its practical 

 bearing. The enormous chemical activity of the light 

 of burning magnesium is well known, but the results 

 stated quantitatively will be startling to many. Accord- 

 ing to Eder (to quote a few examples) the light in a 



1 \Vc .ire much in want of some term to dislinguish the scientific student 

 of phot<graphy from the ordinary camera-carrying pictureta.er. the 

 relationship bmccn the two classes is much about thesameas th.it between 

 the bird and .inimal slulTtr and the '■ natur.llisl" w!io.e dcMjnation he 

 ad..pts. The deviKuation " luciicribe " is quite as .appl.cable to those who 

 piacti-c the art only, but it does not seem sudicienlly harmonious to suggest 

 Its adoption. 



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