#17_kantor_en_0802:#17_kantor_en_0802.qxd 21.05.2009 20:48 Page 143 New data on minerals. M.: 2003. Volume 38 143 UDC 549(084.12) PHOTOGRAPHING MINERALS Boris Z. Kantor For art or technical photographing minerals in nonprofessional conditions, high quality of medium magni- fications can be ensured by means of miniature single lens reflex (SLR) cameras of general use and ordinary photographic materials. To apply longfocus macro lenses and avoid diaphragm excessive closing is recom- mended. To reproduce morphological features of a mineral, flexible and multifunctional artificial lighting is necessary. For negatives, daylight film in combination with lightconversion filter is recommended. Adequate reproducing of mineral complicated color involves accurate matching of color temperatures and selection of light sources, preferably halogen lowpower coldlight lamps, corresponding the given combi- nation of photographic material and colorconversion filter. 7 color photos, 2 references. Photography expands appreciably our tographer’s taste, competence, and miner- no tion of the mineral kingdom. In skillful alogical interests, let us define technical hands, even a plain shatter may be lifted, in preconditions of mineral successful pho- its information and esthetic value, from the tography under these «amateur» condi- waste bin up to the level of museum speci- tions. men. An experienced photographer would A mineral photo should be sufficiently never disregard those fragments, minia- sharp. Viewing, from the usual reading dis- tures, and unpretentious petty crystals that tance (25–30 cm), a picture up to 15 or are usually ignored by museums and col- 20 cm in size, a person with normal eyesight lectors. At the same time, a large specimen discerns not more than 8 or 10 lines per mm attracting general admiration and exposed (400–500 dpi). Accordingly demanded res- in its own separate showcase would hardly olution of a miniature (24 x 36 mm) nega- look equally spectacular on its small or tive is 50–60 lines per mm (2500–3000 medium size photo. Photography also gives dpi) maximum. This is fairly achievable full scope for any kind of interesting with the presenttime photographic lenses artexperiments with minerals. and medium speed films (ISO 100–200). Provided a well tooledup professional Technically perfect pictures can be made, studio is available, the technique of photo- so, with an ordinary miniature SLR camera, graphing minerals differs little from the including any one of the amateur class, and ordinary closeup photography (Scovil, ordinary photographic materials of general 1996). However, mineralogist and photog- use. rapher professions combine only seldom in A medium format camera even enables the same person. More often, a mineralo- creating a «reserve» of resolution for an gist – specialist or hob by ist– has no occasion of manufacturing larger magnifi- access to the expensive special cameras as cation. However, popular rollfilm cameras well as studio lamps and other professional (e.g., PentaconSix or Exacta66) have com- equipment. To illustrate a book or a paper parably massive mirrors which entails or simply to picture minerals occasionally harmful vibrations during the process of for his own pleasure, he is obliged to exposure. As a result, the resolution is accommodate to the homely schedule of appreciably diminished and so the medium the socalled pop photography: picturing format advantage reduces to nothing. A with a general use camera with succeeding good tripod diminishes vibration but can- processing and printing in a minilab. not eliminate it entirely. It is less noticeable Setting aside purely pictorial problems, on condition of short enough (not more who se solving depends entirely on the pho- than 1/100–1/180 s) or long enough (not #17_kantor_en_0802:#17_kantor_en_0802.qxd 21.05.2009 20:48 Page 144 144 New data on minerals. M.: 2003. Volume 38 less than 2–3 s) shutter speed, which is, The possibility of the lens aperture to be however, not always accessible. Another closed down at least to f=32 is advisable. way is to expose by switching the light on Ho wever, closing down should not be over- for the metered time after the shutter has used. Sometimes, it contradicts the pictori- been previously opened in darkness. The al task; in addition, it affects adversely ima - latter may entail, however, a shift of color in ge quality. According to our data, the reso- the red side because of the light source lution of Canon EF as well as Sigma EX thermal lag. ma cro lenses is maximal at f=8 and drops So the balance of advantage should be by 20–25 per cent at f=22, and even by lain with miniature cameras. On condition 40 per cent for the Sigma EX 2,8/50 macro of using a tripod, the vibration in this case lens. is inconspicuous. In addition, some minia- To choose the type of light sources is a ture cameras are provided with the option primary task. In photographic sense, min- of shutter release delay after the mirror has erals are fairly complicated objects. This been lifted, which gives additional assur- implies the use of not less than three or four ance. autonomous light sources supplemented At the same time, the larger format is with reflecting cards of white paper and preferable for slides, as they need, in this aluminium foil. The gleams of faces and the case, no magnification to be viewed. whole light pattern are very much sensitive Minerals are mostly photographed in to the illuminator positions. This implies a closeup regime, i.e. with magnifications literally precision setup of light. It can be up to 1:1, sometimes greater. As the camera achieved on condition the illuminators are standard lens cannot be focused from the enough mobile. demanded short distances, one lengthens it By this reason, the «noncontrolled» su - with an extension tube or bellows or pro- nlight only finds a limited use, and so elec- vides with a closeup lens. However, both tronic flash without pilot light. The tung- mentioned entail deterioration in the image sten lowpowered lamps are mostly used, as quality, since the camera standard lens is they do not provoke photographer’s weari- corrected for «infinite» distance and does ness of too intensive light and heat radia- not, in the mentioned case, answer its pur- tion that is also ruinous for some minerals pose. Essentially better images can be pro- like native sulfur or realgar. Mounted on duced with a macro lens as its optical sys- miniature stands, the lamps may be easily tem is specially corrected for closeup dis- moved along the surface of the table, an tances. In particular, not too expensive improvised shooting stage. A miniature lenses of the Sigma EX macro series are remotecontrol station with individual tog- noteworthy; they are put out for all the gle switches for illuminators would enable basic SLR cameras of modern generation photographer to set up lighting not draw- (Canon, Nikon, Minolta, and Pentax) and ing away from the camera viewfinder. produce high quality images. Adequate reproducing of mineral com- For mineral photography, a macro lens plicated and whimsical colors is a most with focal length about 100 mm is the best. urgent problem. It facilitates well the illusion of third In the process of minilab printing, color dimension and perspective, is accommoda- rendition errors of a negative can be cor- tive in operation, and, compared with rected to a small degree only; besides, this shortfocus lens, less liable to light diffrac- is only possible after the draft copies have tion in the diaphragm hole. been made and studied. As to color slides, Despite of the common opinion, the use they cannot be corrected at all. To correct of a longfocus lens does not entail dimin- color completely is not always possible ishing of the depth of field. According to even by means of editing files obtained by calculations, the depth of field at closeup scanning original photographs. So it is very photography is proportionate to important to avoid errors when taking pic- tures or, at least, to minimize them. The f(M+1)/M2, pledge of success is the proper choice of film, light filter, and light source types with where f is diaphragm number and M is matched color parameters: image magnification. Therefore the depth 5 5 of field does not depend on the focal 10 /Tl – Мlf=10 /Тf, length. #17_kantor_en_0802:#17_kantor_en_0802.qxd 21.05.2009 20:48 Page 145 Photographing Minerals 145 where Tl, Тf – color temperatures, men, with no pattern, spot, and texture. A Kelvin (K), of light sources and film, Мlf – neutral gray background is universal. A filter conversion degree, decamired. highlight spot on the background behind The film choice is only confined to two the photographed object would «lift» it and types balanced either for day (sun) light or intensify volume illusion. A photoprinter tungsten light with color temperatures, file printout of gradual passage from white accordingly, 5500 K and 3400 K. The choice to dark gray color, with the dark side up, is of lightconversion filters is also limited. a successful solution. The background Purplishblue filters are usually used with should be placed at a sufficient distance to conversion degree either 12 or 15 de ca - avoid shadow falling from the specimen. mired (marked as B12, B15 or Wratten 80B, All the modern miniature SLR cameras Wratten 80A). On the other hand, the mar- are provided with automatic exposure me - ket assortment of lamps is fairly rich, and, tering. Having chosen the aperture priority furthermore, they are much cheaper than function and set up the proper diaphragm lightconversion filters. So it is reasonable number, one lets the camera to set up the to select lamp type matching one or two proper shutter speed. On the condition of film — filter type fixed combinations.