It is now possible for any amateur photographer to produce first class work without great cost. Cameras, plates or films, papers and chemicals are now of high grade quality and reliability, and it is only necessary for the operator to use the best appliances he can afford and to expose, develope and print properly, to be certain of good results. Before exposing any plate or film the working of the lens shutter should be thoroughly examined and understood. The Iris diaphragm next should be clearly understood. The various openings of this may be marked in one of two different systems. In one called the inten-sity ratio system the diameter of the diaphragm opening is taken in relation to the focal length of the lens, i.e., if the diameter of the opening is one eighth of the lens's focal length, then that is marked f/8 and so on. With the same lens the light passed by the different stops is proportional to the areas of the different openings, and there-lore proportional to the squares of their diameters, anil therefore the exposures required are proportional to the squares of the denominators of the intensity ratios, that is to the square of the figures in say f/4 and f/8 equals 16 and 64 respectively. Which means that the exposure using stop f/8 requires 4 times the exposure that would be required if stop f/4 were used. In the Uniform System the different stops are denoted direct by numbers which show the relative exposures required. The connection between these two systems is shown by the following figures :-

U.S. No. 1, Intensitv ratio, f/4 ; 2, f/5-7; 4, f/8: 8, f/ll:3; 16, f/16 ; 32, f/22-6; 64, f/32 ; 128, f/45-2; 256, f/64.

It is of no great moment as to which system has been used in marking the stops, provided that it is clear as to which has been adopted and that the user is aware of it. Generally it can be arranged that for most subjects three different stops cover the range required, this simplifies the work of deciding upon what exposure is to be given.

On the question of diaphragm stops Messrs. Kodak, Ltd., say :-

" f.6.3.-For quick exposures of moving objects on ' Clear' days, use 1/100 second; occasionally for slower speeds on hazy and cloudy days ; also for portraiture (see pages 244 and 245).

f.8.-For instantaneous exposures, using 1/25 second, on ' Grey ' or hazy days, and use 1/50 or 1/100 second when the light is * Clear 1 or * Brilliant,' respectively. For scenes on streets that are narrow and somewhat shaded, use 1/5 seconds.

f.ll.-For ordinary outdoor work such as nearby landscape showing little or no sky, groups and street scenes, when the light on the subject is ' clear,' use 1/25 second.

f. 16.-For open views, when the sunlight on the subject is unusually 1 brilliant' and there are no heavy shadows such as views at the seashore or on the water, use 1/50 second ; for ordinary landscapes, in bright sunlight with clear sky overhead, use 1/25 second ; also for interior time exposures, the time for which is given in the table on pages 243 and 244.

f.22.-For instantaneous exposures of extremely distant landscapes, sea views, snow scenes and clouds only, in bright sunlight, use 1/25 second; for ordinary landscapes, street scenes, or nearby subjects when the light is 4 brilliant,' use 1/10 second ; also for time exposures.

f.32 and f.45.-For time exposures out-of-doors on cloudy days, the time for which is given in the table on page 244. For interior time exposures, see page 243. The smaller the stop the sharper the picture, see table on page 244. Total failure will be the result if stops f.32 or f.45 are used for instantaneous exposures.

Throughout these instructions, the exposures given for out-of-door subjects are for hours from 21/2 hours after sunrise until 21/2 hours before sunset. If earlier or later, the exposure required will be longer. For subjects in the shadow under porches or under trees, no definite directions can be given; experience only can teach the proper exposure to give."