1887 



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HO"W TO MAKE YOUR OWN DRAW^- 



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fKIENI) 1UK)T:— Accordinfi to my promise in 

 Gr^KANiNc.s, )). TvU. 1 will now give you and 

 jour i-eaders a dcsciiptlon of my camt'ni ob- 

 scura. This apparal us consists of two parts— 

 the camera-head, and ttic camera, or box. The 

 camcra-iicad, whicli is the principal jiart, is a box in 

 whicli the- lens and mirror are pla(!('d. The mirror 

 reflects the picture throujih the lens on to a sheet 

 of white paper placed or fastened on the bottom of 

 the camera (box). The mirror must face the object, 

 of which a picture is wanted. The artist must 

 therefore have his back to the object. A black 

 cloth or thick blanket is thrown over the top of the 

 i-amera (not over the canicra-head), and must cover 

 the artist's head and body, so as to exclude as much 

 liaht as possible. The darker the camera can be 

 made, the brighter and more distinct will be the 

 picture. The artist may sit in the shade, and this is 

 preferable, as it is liable to become uncomfortably 

 warm under the cloth: but the object must be in 

 clear sunlig-ht, to get a good pictui-e. 



In the " Artist's camera," which you used to sell, 

 the picture is a •' negative;" that is, what is on the 

 right hand of the object shows in the left hand in 

 the picture, and vice \ersa. In this camera the 

 picture is a " positive, "'and shows the object in its 

 natural position. cThe picture in this camera will be 

 about 10 by 12 inches. 



From James W. Queen \- Co., maiuifacfuters of 

 mathematical, oi)tical. and philosophical instru- 

 ments, '••24 Chestnut Street, Philadelphia, I obtained 

 a :}-inch, double-convex lens (focus 2(1 to 2(;i'/4 inches), 

 and a 4 X 6-inch mirror. The two glasses cost me 

 ^iM postpaid. From their letters T copy the tol- 

 lowing: 



"The mirror should be placed close to the lens, 

 otherwise the size of the picture will be reduced." 



"The lai'ger the lens, the greater the brilliancy of 

 the picture; and the longer the focus, the larger 

 the picture." 



By experimenting 1 have found that for the .size 

 of picture f wanted (10 x 12 inch), J have got the 

 distance between lens and mirror about right. A 

 shorter distance would make the picture too large 

 for my puriiose. (,)ueen \' C<i have camera-heads, 

 mounted in brass, which they sell at *.5.00 and $7.50 

 respectively : also a complete camera obscura at 

 *20.00, and a smaller size at *lT.."iO (see their cata- 

 logue of microscopes and accessories, p. 1). But 

 they said that the lenses are rather small, and that 

 I would get better pictures by ahonie-mHde camera- 

 head witli ali-inch lens. 



By the drawings, which 1 will now explain, you 

 will see the construction and dimensions of the 

 camera-head. 



Tt is made throughout of 'n-inch boards, except 

 the little front-piece of the slide, which is scant 's 

 inch thick. 



Fig. 1 gives a front view, showing by the shaded 

 portion the opening through which light is admit- 

 ted to the mirror. Above this opening is a little 

 board, a, fastened with 2 screws, so that it can be 

 removed when it is necessary to take the mirror 

 out to clean it. At the bottom you see two grooves, 

 /)'», in which the slide holding the lens is inserted. 

 Below these grooves a thin strip of wood, c, is nail- 



ed On the inside of the back of the camera-head. 

 This strip need be only ',; inch thick, and forms the 

 second and last exception to the general measure ol 

 ',; inch thickness, mentioned aliov<-, where I failed 

 to notice it. The top edge of this little strip should 

 come even with the under side of the slide, when 

 this is in place. Its object is to prevent any light 

 from coming through at that place. For the same 

 purpose, the lower edge of the front side is rabbet- 

 ed at (I, and in this rabbet tits the thin strip which 

 is nailed on the end of the slide (c, Figs. :! and li. 

 No light should, il possible, be admitted to the cam- 

 era when in use, e.xceiit what comes through the 

 lens. It is, of course, impossible to exclude all 

 light from below; but the less the better. 



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Fig. 2 IS a sUh' view of the camera-head. The diag- 

 onal dotted lines show grooves cut in the inside ol 

 the side-pieces, at an angle of 4."> degrees, in which 

 grooves the mirror sits. The low-er edge of the 

 mirror re^t-- against the back of the camera-head. 

 The horizontal dotted lines, /», near the bottom. 

 show the grooves in which the slide fits. 



Fig. 3 is the slide which holds the lens. With an 

 expansion-bit, a three-inch hole is cut from above, 

 about two-thirds thiough the board, and then llnish- 

 cd with a hole 's inch less in diameter. The lens 

 rests on the shoulder which is thus ma<le in the 

 hole. The larger (upjier) part of the hole should be 

 reamed a little, so that it will be larger at the shoiil 

 der than at the tojt. .\n open ring of brass wire is 

 pressed down on top of the lens, to holil il in placi-: 

 and as the hole is flaring, the ring can not come out 



KiMT- '■' is tim lartff l" reprexfiit in propurtimitil wizcancl i> 

 therefore greatly reduoeil: heuee it liears no pioiiin-tioii to the 

 other ligiiies. Fifys. 1 and 2 are representeil by X in Fijr. 6, the 

 latter simply showing the box and now Fi(f!». land '.' are i>laeed 



