Movie Makers (Jan-May 1928)

CLOSE UP Work for Advanced Amateurs EVEN the most elaborate amateur cameras are purposely made to operate as simply as possible. The constant speed mechanism and the fixed-focus lenses supplied with these instruments, leave but a single variable factor, namely, the diaphragm. This serves to reduce the problem of taking moving pictures to its simplest form. It becomes merely a question of varying the diaphragm to compensate for different conditions of lighting. But the very simplicity of the instrument serves to introduce some compensating disadvantages and limitations in its use. To obtain clear and sharp pictures on a 16 m.m. film, it is of primary importance that the object should be in exact focus — otherwise, the projected picture will appear blurred and hazy. With a fixed-focus 1-inch lens, critical sharpness can only be obtained if the object is located beyond a predetermined distance from the camera, known as the "hyperfocal distance." Professionals aim to take pictures with the greatest possible degree of sharpness, or as they express it, the image is photographed with "circles of confusion" not exceeding 1/1000 of an inch. Expressed in other words, this implies that each individual light ray is photographed as a dot measuring not more than 1/1000 of an inch in diameter. However, in good amateur work it is possible to obtain fairly sharp images with circles of confusion approximately 1/500 of an inch. The figures given in Table 1 furnish some idea as to the minimum distance from the camera (i. e. "hyperfocal distance") that an object may be photographed to obtain pictures in sharp focus. H^cY^otaZ, ~X>Cs\.tMJU.l 1— Ius. UskC QrCtiaO. "WbrK (Ci'tcle 0e ffo*UiSu>K OroUVaA* "Wo**; '/too'-) Fig 46 + a 23.2, Ft P. a^ 3J3 IC-fc F.a.T 3o-1 IM F.3-r ij.g II-1 P. 4 20-8 lo-4 F.4-S" l8-r 12S F.S5 IS--I" *IL F.8 Ml |04 3-8 RH sa. It. TABLE 1 Note — The Filmo camera was used in these experiments and the described attachments were designed by the C. P. Goerz American Optical Co. By Herbert Abraham With Illustrations by the Author Thus the larger the diaphragm that is used, the further away from the camera the object must be. This makes it practically impossible to use the fixed-focus lens to take "closeups", unless the object is taken in the strongest sunlight with the smallest diaphragm or stop. Even under the most favorable lighting conditions permitting the use of an / 16 stop, the object must be at least 5.8 ft. from the camera to obtain maximum sharpness, or 2.6 ft. away to obtain fairly good results. To overcome this limitation, some manufacturers are prepared when specifically requested, to furnish the lenses in focusing mounts. But this introduces another complication — the operator must estimate the distance of the object being filmed. This is not always as easy as may at first appear, unless the object is sufficently far from the camera, or unless the light conditions permit a small diaphragm being used, when the depth of focus will permit of considerable latitude in the distance' seting of the lens. Table 2 shows the depth of focus for a 1-in. lens giving a circle of confusion of 1/500 of an inch : Etprtv ot T"ocu,3 IS Li.!. (Ccrelt ol Cow£usi»>* 'As»Uf). D.«U-£e Ob. FI-6 F2S F17 F3-5" F4 F4.S FST.5 F8 fii If it oo Wot.. itta 00 IS4S CD CO 1045 CO T2SE. 00 7-te CO 5-.2C CO 3BB CO 2t«^00 *»i£ OO lev 00 loa. oo 8500 >-8 00 To 00 tor 00 44 OO 34 00 K-4 00 lo-7 I45-. 1-J CO 81 oo IAS CO t.sr 00 4-3 00 ST OO 4.1500 31 CO 23 CO *afc 1-1 42.4 11 (Ft. Ii 578. tfc CO ^7 CO for 00 CO J.I 00 2-1 CO '** {{£. 7J y-o 4J.0 t.7534 J to OO 00 r-ir CO 4.tr 3-t OO 2-1 00 21 00 '<>* iz To I7J t2r 2SO (■1 2g-r R45 Or S-l 240. 4-8 OO 4,3 CO 3.4 CO S.-W CO 2.05OO 8 a fp*~ 122 S-4 1S3 •T3 lt-7 4-8 24.4 *■£■ 34 1 4-3 3? CO 32 00 2t CO 2-0 CO 6B K~ 4.8 81 44 7-3 4.3 40 /»-l 3-8 142 3-tr 171 3.35 28-r 2-8 CO 2-3 CO 1.8 00 4.1 fe.4 3. or 7-ir 3 8 7.4 8-£ 3.4 9 7 3-2T lo-l Jo I4.t 2.5 130. 22 00 1.73OO 4A w 3.8 Rt 35T t-s, 3-r t-4 3J 31 3.0 8-73" 28 11 2-4 33.4 2-I OO IT 00 43 1 Km 3-4 44 3-3 SA 3-2 3o to tr 2-8 To Jt 5-4S 2-3 17-3 2-0 CO It 02 3a ] Mol, 2-7 3 + 3-tS" 3-7 54 4.0 2-3 4.3 2-3 44T 2-154-?5 1-1 7-/ I 7 ir, 14 00 z*± \ NW I8r 4-2 1-8 S-3 53 IT »4 IV 5 5" 1-7 2t l-t 2-8 l-i" 3-3 I -3 44 115 10.7 msl *cw IM'i 113 IHIS 11-1 ll.4a 2o-6 1MB 2.1-4 IIAB 210 Ito'J! »-t is-ta •at, IMIS 3S2 fat 1ft SUu* lit | II-4 I2s 11-3 III 152 M'O 1335" 101 13-t lo-l 14.0 102 11 i<\ lit J20-t • H^-pt-vfocal Dtstan^t. TABLE 2 It will be noted that the depth of focus is reduced under the following conditions: (1) The nearer the object is located to the camera, and (2) The larger the diaphragm that is used. Thus on taking a close-up of a person estimated to be 3 feet from the camera, using artificial illumination requiring a stop of / 1.8, sharp focus will be attained if the subject is actually between 2.7 and 3.4 ft. from the camera, or within a range of .7 ft. If the subject is closer than 2.7 ft. or further away than 3.4 ft. then the image will be blurred. On photographing objects closer than 3 ft. the latitude becomes even smaller, so that is becomes necessary to use a range finder or measuring tape, otherwise the chances of obtaining the proper focus will be provokingly remote. Moreover, if the object is nearer than 4 or 5 feet, another complication will arise, in consequence of its being photographed out of center. This is due to the fact that the viewfinder tube is parallel to the axis of the lens, and located 1% in. to its left. As a result, the nearer the object is located to the camera, the more it will be photographed out of center, if taken through the usual view finder. Fio.l o .-j To overcome the foregoing uncertainties, two simple attachments have been developed, known as the "focusing microscope" and the "compensating-base," illustrated in Figs. 1, 2 and 3. 0 Thirty-nine