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Techniques of Close-Up Photography with a Single-Lens Reflex Camera MARVINR

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Techniques of Close-Up Photography with a Single-Lens Reflex Camera MARVINR Techniques of Close-up Photography with a Single-Lens Reflex Camera MARVINR. BELL Assistant Professor, LaboratorySchool, Indiana State Teachers College, Terre Haute The single-lens reflex camera differs from the conventional camera in that the latter is focused by means of a view-finder that is some- what removed from the camera lens. This Downloaded from http://online.ucpress.edu/abt/article-pdf/21/6/238/16026/4439154.pdf by guest on 30 September 2021 is of little consequence when taking pictures of objects some distance away but does make a difference in close-up work as will be ex- plained below. The double-lens reflex camera has a full size viewing plate which permits sharp focus and accurate composition. The viewing lens is separated from the "taking" lens far enough to create the same problem in close-up work as is encountered with the con- ventional camera, and for the same reason. This difference in viewing and takinig linz of sight is known as parallax which can be compen- sated for by raising the camera or by using an anti-parallax device. s~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~X...... .. .... ~~~~~~~~~.... .. .. .. ... .. .. .. .. ;.- .........-.. .. .. .... ........... ....~~ ~ ~~~ ... .. ......::... .... ............. .... ............ ...... ... .. .... ............. ................. .. .... ... ~~~~~~~~~~~~~~~~~~~~~... .- ... ....... ... , ; ....... : .. : . .. .. .. ............. ....... .. _. .........s ... ..... ..... .. ..... .... .. ... ... ..... ......... : - _=.....8S:\: . ... .... ... ..... .. .. _.:-:........ ;::.:..:_. ......... .. .. ......... .. ... .. .. .. .... -.. :;............... .. .. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.. .. .... .. ...... ... FIGURE 2. The extension here is about 100 mm. (4"); .. .... .: .......:.:. A,...._ ' : _ the magnification is 2X. Note the use of tripod and ...... ..'. :...... cable release to reduce vibrations. ... FIGURm..... .si .n l ns ...r....e... c....... ... :............:.:. .:.:.:::. .::::: means of a 450 mirror set beneath the ground glass viewing plate. This mirror comes down into viewing position when the shutter is cocked and goes back up away from the film when the shutter is released. The operator :lls........ ... ............ ...;: always sees exactly what the film "sees" re- FIGURE1. The 35mm. single-lens reflex camera show- ing an extension bellows and a 50mm. extension tube gardless of the distance between the lens and set inserted between the camera body and the lens. subject. Techniques in close-up work. Close-up The single-lens reflex camera views and photography (not photomicrography) may focuses through the same lens that takes the be accomplished in two ways. For cameras not pictures, thus eliminating inaccurate focus and having removable lenses, supplementary lenses composition regardless of how close the lens may be used. These are commonly referred to is to the subiect. This is accomplished by as "portrait" lenses and are simply slipped over *Presented at the NABT sessions during the AAAS the camera lens to give added magnification. meetings in Washington, D.C., December, 1958. Unless the camera used is of the single-lens 238 Vol. 21, No. 6 TECHNIQUES OF CLOSE-UP PHOTOGRAPHY 239 reflex type, the focus usually is determined by undesirable, because a blurred background measuring and the picture composed by using may enhance rather than detract, and very a framing device made of bent wire, attached small dots of bright light appear on the slide to the front of the camera, or some other anti- as small or larger circles of light depending parallax device. upon the extent to which they are out of focus. Extension devices. The second method is This shallow depth of field increases the based on the principle that the closer the sub- need for very careful focusing. This is always ject is to the camera, the larger its image will done through the magnifying glass over the appear on the film, and the closer the subject is, viewing plate and with the iris at its largest the farther the lens is moved away from the opening. the iris is stopped down to the de- film to bring it into focus. But there is a limit sired opening just before releasing the shutter. to the distance the lens can be screwed fore- Another precaution here is that the camera ward. With cameras having removable lenses and the subject must both be perfectly still at Downloaded from http://online.ucpress.edu/abt/article-pdf/21/6/238/16026/4439154.pdf by guest on 30 September 2021 this distance can be increased considerably by the moment of releasing the shutter. The inserting rings, tubes, or adjustable bellows be- slightest movement will cause the picture to tween the lens and the camera body, Fig. 1. be blurred. The work must be done where Extension tube sets commonly consist of three there is an absence of air currents, if the sub- or more tubes that can be used separately or ject is of light material. A cable release should in any combination. Thus a 50mm. tube set be used to reduce any vibration caused by has three tubes, one 5mm., another 15mm., and releasing the shutter. For the above reasons, a third 30mm. Possible extensions with this set the camera must always be supported on a are 5mm., 15mm., 20mm., 25mm., 30mm., tripod or other solid object, Fig. 2. 45mm., and 50mm. Exposure. Because the light must travel a Extension bellows accomplish the same re- greater distance from lens to film in close-up sults, with the added advantage of (1) extend- work, it is necessary to increase the exposure ing farther, and (2) continuous extension from time or to use a larger iris opening. It must be about two inches (50mm.) to six inches (150- remembered, however that the larger iris mm.). Extension tubes and extension bellows opening decreases the depth of focus, so it is can be used in combination with each other. better in most cases to use the smaller opening Magnification. The amount of magnification and increase the time proportionately. The depends upon the focal length of the camera accompanying table gives data on this and lens and the amount of the extension. The other information for several extensions from normal lens on most 35mm. (size of film) 5mm. to 175mm. cameras is 50mm. This means that the lens is The extensions are found in the first column, 50mm. (2 inches) from the film. If by means see table. Fifty millimeters (the focal length of extension this lens can be moved another of the lens) added to each of these gives the 50mm. from the film the subject will be in lens-to-film distance found in the second col- focus on the film when it is 100mm. from the umn. This lens-to-film distance is used in com- lens, and the image will appear full-size puting the effective apertures for the exten- on the slide. Thus, any extension beyond the sions given in the third column. The exposure focal length of the lens will produce a picture and aperture, determined by a light meter, that is actually magnified on the film. A small are taken to be 1/25 second at f/Il when no object, magnified four times, may still be small extension is used. The proper aperture for 1/25 on the slide, but when projected to the screen second for any extension can be calculated by it will appear quite large. the equation: A=a x f where A is the ef- f +e' The depth of focus becomes narrower as the fective aperture for the desired extension: a lens is moved closer to the subject, and at very is the indicated aperture (from light meter); close range it becomes critical. This is not the f is the focal length of the lens; and e is the case with very flat subjects, nor with copying, amount of extension. Example: The light meter so long as the subject is in the same plane with calls for 1/25 second at f/11, and 50mm. of the film. The depth of focus can be increased extension are used with a 50mm. lens. some by using a small iris opening and in- 50 creasing the time of exposure accordingly. The A=11 x -or A=f/5.5. The new setting lack of depth of focus may not always prove is now 1/25 second at f/5.5. 240 THE AMERICAN BIOLOGY TEACHER October, 1959 Normal Exposure Extension Lens to Film 1/25 at f/1l Magnification Lens to Subject 5mm. 55mm. set at f/10. .1X 18" 15mm. 65mm. f/ 8.5 .3X 9" 20mm. 70mm. f/ 7.9 .4X 63/ 30mm. 80mm. f/ 6.9 .6X 52" 50mm. loomm. f/ 5.5 l.OX 4" 75mm. 125mm. f/ 4.4 1.5X 3?2"i lOOmm. 150mm. f/ 3.7 2.OX 3 l8 130mm. 180mm. f/ 3.1 2.6X 2Ys" 175mm. 225mm. f/ 2.4 3.5X 2V8" Downloaded from http://online.ucpress.edu/abt/article-pdf/21/6/238/16026/4439154.pdf by guest on 30 September 2021 TABLE Column 1. The amount of extension provided by extension tubes and/or bellows. Column 2. The lens-to-film distance is equal to the focal length of lens (50mm.) plus the amount of extension. Column 3. The f/value applicable to the various extensions when the exposure remains at 1/25 second. Column 4. The magnification is found by dividing the extension by the focal length of the lens. Column 5. These distances are only close approximationsof the exact mathematicalvalues, and may vary due to depth of focus, and the fact that the lens can be adjusted from "3 ft. to infinity." If the larger apertures do not give enough The fifth column shows the approximate depth of focus for a particular subject, the distances from lens to the subject, a distance time can be computed for a smaller opening. which may vary, because of the depth of focus, If the same f/value is used (f/Il in our ex- and the fact that the lens can be adjusted from ample) the time must be increased for any "three feet to infinity." This variation is great- extension beyond infinity.
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