148 



PHOTOGRAPHY 



material which, while ixmsessing the t rans|iarency 

 "I glass, should be of a lew tirittle nature, and 

 among the** Mr WiMMllmry in 1K76 produced Hiich a 

 compound frcnii collodion, castor-oil, and Canada 

 lialsam. Tliis mixture, aftr bein^ allowed to dry 

 on a sheet nf glass, wan coated with an cmul-ion 

 wnsitive to light, anil after again licing driiil was 

 Htrip|Mil fniiii its sup|Kirt iiiul nit into suitable si/es 

 for the camera. It is noteworthy also that the 

 inventor at tin- -HUH- time proposed that micli films. 

 lieing|>erfectly flexible, might lie rolled and nnrollcd 

 ( panorama bullion ), so that successive lengi hs 

 mi^lit In- siil, mined tn llie liiininiius image, and 

 tliun the whole business of changing plates lie 

 accomplished hy the turn of a handle outside the 

 apparatus. The same iilea was taken up by War- 

 nerkc :i few years later, and his patented roller- 

 stale liecame obtainable commercially. Warnerke 

 also made a sensitive dry colliKlinn Him for use in 

 his apparatus, but its coat which \vaa at the rate 

 of a penny per square inch limited its use to a few. 



To Messrs Morgan & Kiild of Kichmoiid belong 

 the honour of having first applied a gelatine emul- 

 sion t<> paper. This paper is now made by many 

 dealers, and is commonly called bromide paper. 

 It* principal use is for enlarging, but at the time of 

 its introduction it wast used for negative work, 

 the |Mi|M-r lieing rendered >emi transparent by an 

 after-operation. It must also ! noted, tun. that 

 for this work the inventors employed a roller-slide 

 of tin- kind suggested by Wood bury. The Eastman 

 Company next took up the matter, introduced a 

 i oiler slide, together with a paper Him of very 

 reliable quality. This pajier is sold in spools, 

 reaily wound, so that the buyer had merely to take 

 a siiool from its case, insert it in the roller-slide, 

 and he immediately had material ready for reeling 

 off forty or fifty negatives, to lie subsequently 

 separated by cutting, develo|ied, and rendered 

 transparent with a preparation of vaseline. These 

 films were objected to by some on account of the 

 trace of grain from the pa|M-r which was left on 

 tin- picture printed from it, and a stripping film ' 

 was next adopted as previously proponed by the 

 I'cv. W. Palmer. Hy this modification the sur- 

 face In-aring the image could \>e stripped from the 

 original paper and transferred to a stiff sheet of 

 insoluble gelatine, which liecame its final support. 

 Film photography hits recently lieen brought tn still 



greater perfection by tl mployment of trans- 



|>arent and flexible celluloid in sheet form. It is 

 ciiiious to note that this substance, invented by 

 1'arkes aliout IS-Vi, was long ago proposed as an 

 efficient sultstance for use in photography, and it 

 would doubtless have been so used if collodion, 

 when applied to it. hail not had a solvent action. 

 Hut OH it is quite insoluble in water, it forms a per- 

 fect siip|Mirt for a gelatine lilm, and, now that it can 

 be manufactured nearly as clear as glass, it repre- 

 sents the best thing yet ini induced. Its general 

 use is limited by its cost, which is greatly in excess 

 of glass, but it presents so many advantages that 

 it is very largely employed. The material is now 

 made thin enough to lie wound on spools and used 

 in roll-holders. Itcvond the advantage of light 

 ness, portability, frec<l<nn from breakage, reilured 

 cost of carriage. \-c., which the films undoubtedly 

 |.,,..i ., theie i one gain in their employment, of a 

 I.- lniic.il nature, whieh is important enough to 

 receive recognition here. They an 1 free from hala- 

 tion. Halation is apparent in negatives taken 

 u|ion glass plate* as an encroachment of the light 

 part" II|H.II tho Hark (Mirtions, and is seen in its 

 most aggravated form in the bluriinu out of 

 windows in interior views. It is caused ehiclly by 

 reflection from the l>ack surface of the glass. 



The great rapidity of modern dry plates allows a 

 photograph to ) taken in such a mere fraction of 



a second that the camera can IM- held in the hand 

 dining the o|>cratioii. Various hand eameias are 

 now made, and meet with extensive employment, 

 especially by tourist*, and are more or less dis- 

 guised as despatch lioxes ; hut they are becoming 



I so common that the disguise is more apparent than 

 real. 



The extreme sensitiveness of modern dry plates 



| has also given rise to what is known as thi-b -light 

 pictures, which are photographs taken by the 

 almost instantaneous flash produced by Muttering 

 jHiwdered magnesium into a lamp-flame. Man\ 

 ingenious forms of lani]>s have lieeii devised for this 

 pui|iose. They mostly consist of a spirit lamp in 

 conjunction with a receptacle for the magnesium 

 powder, with a pneumatic ball and tube at (ached. 

 Pressure of the ball urges a puff of air into the 

 powder, and carries it into the flame. This system 

 is much used for taking groups and po> trails at 

 night in private and public looms. The best 

 workers employ a branch tube from the ball, which 

 exposes the lens at the moment of maximum li^hi. 

 Lenses. The quality as well as the kind of Tens 

 used is of great importance. An explanation of 

 the different forms and projiorties ut I iven 



under that head, but it is necessary to say a few- 

 words here about the kinds used in photography. 

 They may lie divided into two classes portrait 

 lenses, and view lenses. The former are of large 

 aperture, but give a small image; while the latter 

 have a small aperture, hut give an image which 

 covers a far larger surface. In the portrait lens 

 rapidity of action has lieen the chief thing con 

 siilered. for it is used in a studio where the amount 

 of light available is always more or less limited. 

 A portrait lens unless of the 'doublet' form 

 is not suitable for view pur|Mises ; but a view 

 lens can well be used for portraiture under cci 

 tain conditions, and is one of the liest lenses to 

 use for groups, t'mler the head of view lenses come 

 a large number which have fanciful names attached 

 to them that are apt to mislead the tyro, but 

 which are all more or less alike. In the early days 

 of photography telescopic objii-tives were made to 

 do duly in the camera, but they gave a very small 

 field, and were in oilier respects unsuiicd to the 

 purpose. Then came (1841) the portrait lens 

 designed by I'et/val, and made by Voigt lander of 

 Vienna, an invention which marks an era in photo- 

 graphic progress. The single view lens, which is 

 the chca|>cst and for pure landscape is still un- 

 ei|iialled. bad its first improvement in the patent 

 aplanatie lens made hyCiriihhin IH.'iT. Although 

 called a single lens, il consists of a combination of 

 crown ghiss of concavo-convex form, cemented to a 

 flint divergent meniscus. The single lens was 

 modified later on by Dallmeyer, who subsequently, 

 in 1888, introduced a new form of view lens which, 



I--- lessill) (he ii n. il adv anla.ui -. I. ad tin- i|ilalll\, 

 lilheiio unknown ill a single landscape lens, of 

 giving an image free from curvilinear distortion. 

 The same feature had licen secured by I lallmcver in 

 his well-known triplet lens, which was invented in 

 IHAO, and which, as its name implies, c. insisted of 

 three combinations. This lens was serviceable for 

 copying, architectural subjects, as well as for land 

 scape, and was a great favourite with photographers. 

 It has now lieen superseded by the doublet lorni of 

 lens, which, under the name of rectilinear, symmeti i 

 cal, &c., is the most commonly used form of photo- 

 graphic objective. It generally consists of two 

 combinations of similar const ruction placed with 

 their concave surfaces facing one another, the 

 necessary slops or diaphragms for increasing defini- 

 tion and i educing spherical aberration lieing inserted 

 in a slit in the brass mounting tube midway ! 

 (ween them. These lenses are constructed to take 

 different angles of view, according to the require- 



