September, 1926 INDUSTRIAL -4ND ENGINEERING CHEMISTRY 915

T R I C T L Y speak ing , i n S 1876 there was

no photographic in- dustry, while today motion pictures can be made by the ama- teur with as much ease a n d a s l i t t l e knowledge as the or- dinary s n a p s h o t s . The photographer of’ fifty years ago manu- f a c t u r e d h i s own materials and went> f o r t h t o t a k e his p h o t o g r a p h s very much as is shown in Figure 2, carrying on his back not only his

Fifty Years of Photography‘ By C. E. K. Mees

EASTMAN KODAK Co., ROCEIESTBR, N. Y.

Figure 1-Photographic Camp in 1876 Showing Photographer and His Assistant Carrying Out Their Operations

camera but also a portable dark room, which he erected in the field (Figure I ) so that he could prepare the sensitive plates for use, c’xpose them while still wet, and develop them before they had time to dry.

The process of that date was known as “wet collodion.” The photographer coated his glass with a solution of nitro- cellulose in ether and alcohol containing iodides soluble in alcohol, and immersed the coated plate in a tank containing silver nitrate solution, which precipitated silver iodide in the film. After exposure, which lasted a second or more in bright light, the plate was developed immediately with an acid reducing agent, which precipitated the silver upon the exposed iodide particles, and the remaining iodide was dis- solved in cyanide solution. After a brief washing, the thin film was dried rapidly and the negative was ready for me. For printing, the photographer either prepared his own paper or bought albuminized paper which had been coated with albumin containing chlorides and which he sensitized himself by flowing on a solution of silver nitrate. The supply of albuminized paper was the nearest approach to a photo- graphic industry which existed in 1876.

The photographic industry owes its development to the introduction of the gelatin process, in which the sensitive salts held in gelatin could be used in a dry state and therefore could be prepared by a manufacturer and supplied to the photographer ready for use. Wet collodion was thus sup- planted by ready prepared gelatin plates and the albuminized paper by paper coated with an emulsion of silver chloride in gelatin, which could be developed in the same way as the dry plate. For most purposes the dry plate wac eventually replaced by the flexible film.

At the present time the photographic industry employs some forty thousand people throughout the world, about twenty thousand of whom are occupied with the preparation of sensitive materials and the remainder with the manu- facture of cameras and the wholesale distribution of the products to the retailer. Photographic manufacture is organized chiefly in modern factories producing on a large scale and using specially designed machinery at every step of the process. I n the largest of these factories the output

1 Received April 9, 1926.

of motion picture film alone exceeds 150,000 miles i n a y e a r . X e a r l y 5 mil l ion pounds of cotton are used each year for the manufacture of film, and over 3 tons of pure silver bullion are used each week. The total power required exceeds 20,000 horse- power, and the con- sumption of coal is over 500 tons a day.

The industry owes its progress largely to t h e e f f o r t s of the chemis ts . This is particularly true of t h e p roduc t ion of

film, the preparation of the flexible support being one of the triumphs of chemical technology. The greater part of this flexible support is made by the nitration of cotton, the nitrocotton being dissolved and spread out to form the thin support. I n addition to the nitrocotton film, which is highly inflammable, a large amount of film is now made from cellulose acetate produced by the treatment of cotton with acetic anhydride and acetic acid.

It is onlv in the last few years that much progress has been made in the study of the fundamental theory of the photo- g raph ic process . This has been partly because of the secrecy which surrounds the a c t u a l processes of photographic manu- facture and especially of emulsion-making, but still more on ac- count of the complex nature of the chem- ica l r eac t ions in- volved. Only wi th the development of modern physical and colloid chemistry has it become possible to study the factors to which t h e sensi- tiveness of p h o t o - graphic emulsions are d u e a n d t o under- stand the nature of

Figure 2-The Amateur Photographer of 1876

photographic sensitiveness and the reaction which the photo- graphic material undergoes on exposure to light. During the last five years, however, great progress has been made in this field, and there is reason to hope that before long a clear and coherent theory of the photographic process will be avail-

916 Vol. 18, No. 9

ahh!. A notable advance has been the discovery by S. E. apparatus and material3 have heen developed t o suit the Rlieppard that the high degree of sensitivoness conferred by requirements of this work. emulsification in gelatin as compared with tlie use of collodion Perhaps the largest field of applied plrotography is in the is due to the presence in the gelatin of smdl traces of organic preparation of engravings, and liere imtil quite recently the sulfur compounds which unite with thc silver bromide and wet collodion process, which was the standard process decompose, forming silver sulfide on the surface of the bro- in 1876, still reigned supreme. Even now by far t,he largest nride crystals. quantity of negatives used for photo-engraving is made on

In one branch of photography the hopes that our pre- wet collodion plates which tire photographer prepares and decessors in 1870 might just.ifiahly have entertained have develops exactly as he did in 18i6. The rise of the rotary not been realized. In 1861, Clerk Maxwell laid down intaglio processes and of photolithography is now threatening the hnsic principles of color photo and in 1909 the half-tone process and with it the wet collodion negative, Duros du Ilauron published a honk he discussed a.nd a t the present time large quantities of photographic all the processes of color photography which he could foresee mat,erial are used in connection with this and other repro- at, that time. Fifty years later, we ust acknowledge that, duction processes. Although direct color photography has

not develoned to anv meat extent,. color renroduction nroc- I esses hav; become ;e;y important, and coiored prints add to the amenities of our dailv life. the nrocesses used beine

Maxwell Lnd du Hauron, mad; of color-sensitizing

s has been made in the last thirty

otographic material ultra-violet region,

which materials are useful has been until it is now common to photograph

sible spectrum In the red and even be- iotorrraphic practice. while in spectro-

I - .

1 scopie work the infia re& 5s far as a u&e length o f one micron, can he photographed wit.hout difficulty (Figtire 3). Figure 3-Photographic Seneifivity Today

while we have been able to realize the proeemes which du Hauron suggested, we have made practically no advance beyond them, and that color photography is still so difficult in operation that there are only a very few workers in the art throughout the entire world; moreover, the processes which we are using do not show any possibility of developing in such a way that colur photography may have the wide- spread distribution that monochrome photography has at- tained. It is, indeed, generally considered by workers in photographic science that we shall eventually have to dc- velop some entirely new system of color photograplxy, depending upon principles quite different from those which du Hauron suggested or which have been proposed up to t.lre present day. Of such a system we have at tho present time, however, only a few slight suggestions.

The applications of photography a t the present time are extremely wide. Photogaphy is the handmaid and tool of all the sciences. The astronomer, who in 1876 would have

a1 observation, today would use spectroscopes of fifty years ago

nd textbooks; the modern spectro- ally. The microscopist is turning

to ilie photographic plate as a standard tool, and i t is not unlikely that in the near future the microscopist will expect to photograph what he cannot see and will use the eye chiefly as a finder for the camera.

Tlic discovery of the x-ray in 1895 opened a new field of photography which bas g rom to so vast an extent that a t the present time more films are used for radiography than for portrait photography, and it might almost he said that tlie aver%@ citizen is more likely to have a photograph taken of his stomach than of his face. The radiography of tho teeth is now very common, but probably in a few years radiogrirphie examination will not be a special operation but a routine procedure during dental surgery.

The application of aerial photography, developed to such great proportions during the war, to peacetime surveying presents considerable difficulties, nevertheless, a large amount of aerial photography is done in every country, and special

FiBvre 4-The Modern Amateur Photographer

The photographic industry, lrowever, would still be a sinall industry did it not include that extraordinary de- velopment-motion pictures. The first rcproduction of movement in the early nineties developed very rapidly until i t is now one of the great industries of the world and almost everybody goes to the "movies"-so that the photo- graphic industry, nonexistent in 1876, is in 1926 dwarfed by its child. It is not impossible that a still greater extension of photography will he found in the application of the princi- ples of motion pictures to amateur photography (Figure 4).