The international photographer (Jan-Dec 1934)

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March, 1934 The INTERNATIONAL PHOTOGRAPHER Nine size, as in the case of looking through a doorway, window or a porch. The proper perspective is then figured hy measuring from the full size to the miniature. SIDE ELEVATION 5 = " . «■ HiNIKTURg //V F4ACTiOA/f of AFOOT 0 =■ DlSTAUCt FROrl L CHS. To FULL S'Z f tfJ F££ T ft oiSTAvcr rnon lcns to mini^turc m re ft NO 3 -* /V04 -* no. 5 -*■ N o D N D NO S D — 25x100 t-iS s 250 S = 10 ft. N =50 I 3. N 12' Fig. 2 For instance, we are photographing an interior. Through the open doorway we should see a certain group of buildings which, according to the locale of the picture, would be 600 feet distant. Owing to small stage room and lack of space we have only about 30 feet in which to set the miniature, using Formula No. 5, N = SD. N = distance in feet from open doorways to miniature. S= scale of miniature in fractions of a foot. D = distance from doorway to full size of original buildings. We will now try the J^ inch scale and see how it 1 600 works out. N = — x . N = 25 feet. 24 1 We now know we can build the miniatures to the y2 inch scale and set them 25 feet distant, from the doorway to the nearest miniature and have the proper perspective. This same system can be applied to other groups of miniatures in a combined shot ; they can all be built and set according to the above system. When photographing miniatures not in the same shot with full size, this makes the layout a matter of building to any desired scale, and that alone, and setting the camera wherever desired for the perspective and composition. It is well to mention here, that the speed of moving miniatures, should be measured in the same ratio as the scale to which they are built. The next problem to be considered is that of a projected background. In this case we have a tree 100 feet high which we wish to project on a screen 25 feet from the camera lens. The proper size of the projected image should be considered. To find out accurately we can proceed as follows: Let S = height of projected image. 25 feet = distance from the camera lens to the screen. 100 feet = height of the object. 250 feet = distance from the camera lens to the object. O perspective to this same tree and man beside it, the same formula works, except we transpose it. S O N D = D NO Let s N O D D = S = 4 ft. = 25 = 100 = perspective, or distance. 25x100 4 Ten feet is the height of the projected image. See Fig. 2. We will now take the problem of giving a desired D = 625 feet. This is the effect it will show in the background. As a rule most process cameramen are satisfied to trust their eyes to give them the proper size and let the perspective take care of itself. Excellent eyesight and years of experience help them to do this without any trouble. But when in doubt, it's nice to have the rules of mathematics to settle an argument. To the readers who want to try a new system, on depth of field for a selected lens, we will take the problem of the hanging miniature and work out the lens stop and distance to be focused on for sharpness of field, the accompanying diagram will illustrate the fundamentals. (See Page 10.) X=144X12"=1728 inches = = far distance y= 12XL2"^ 144 inches = near distance f== 1.575 inches = focal length of lens d^ .002 inches = circle of confusion s= = stop number Dt= = distance focused on First we will solve for the proper stop which will bring in these separated points sharply, using a circle of confusion of .002 of an inch ; and using the following formula which is stated in terms we alreadv know: f2 (x-y) S = 2yxd— fd (x+y) Substituting in the values we have: 2.48 (1728—144) S = 2.X144.M728\002— 1.575\002 (1728+144) S = 3.97 which for practical purposes we can use stop f :4. Now we must find out which point to focus our lens on, to get best results. Using the following formula: f2 (x-y) D= + f dS (x+y) Please mention The International Photographer when corresponding with advertisers.