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University of Michigan University Library ?-? 27 - !.I- ------A- **-s.r=x='-6 - T-*- -x= &=+* "+ * Museum of Paleontology 4 111 PAPERS ON PALEONTOLOGY *I PROPERTY O sElj,ri ;:>I :,,c TQ..-FF-,LEGfibJG.'f +I ,-'..= ' -..II.c. ..-. I i ,7,\i'i ; 2,r:i,g.::i,,-+..:.: ;.:j.; Ill Planning Photography of Microfossils iii BY Robert V. Kesling iii I 64~fi 4*=4ItS--44=4*O - CONTENTS OPTICS ................................. 1 Accelerator ......................... 27 Light ................................ 1 Restrainer .......................... 28 Reflection ......................... 2 Preservative ........................ 28 Transmission ....................... 2 Rinse bath .......................... 28 Absorption ......................... 3 Fixation ............................ 29 Refraction ......................... 3 Washing ............................. 29 Diffraction ........................4 Drying .............................. 29 Lens ................................. 4 Water used in making solutions ....... 30 Focal length ......................... Image size PRINTING ............................... ........................... Procedure Speed of the lens .................... ........................... Circle of confusion .................. Contact ........................... Hyperfocal distance Projection printing ............... .................. Types of paper Depth of. field ...................... ....................... Contrasts Subject distance ......................... ................... Finishes .......................... Circle of confusion ................ Weights ........................... Focal length ....................... Diaphragm opening .................. 9 PROCESSING ROUTINE .................... 31 Definition ........................... 9 Precautions ......................... 31 Lens coverage ....................... 10 Darkroom layout ..................... 32 Equations ........................... 10 Bulk photography .................... 32 FILMS AND PAPERS ...................... 19 REVISING AM3 I-KPROVING TIE NEGATIVE ... 33 Physical properties ................. 20 Factors in processing an emulsion ... 33 Emulsion and halides .............. 20 Proper exposure ..................... 35 Support or base ................... 21 Negative faults ..................... 35 Emulsion .......................... MULTIPLE LENSES Overcoating ....................... ....................... Light transmission of lens Noncurl backing .......... ................... Stray light in lens Antihalation backing .............. ................. Emulsion properties Illumination of field of image ...... ................. Reversible lenses Film speed ......................... ................... Grain ............................. Two-lens system ..................... Color sensitivity ................. Three-lens system ................... Contrast .......................... 23 THE MICROSCOPE AS A LENS SYSTEM ....... 44 Resolving power ................... 24 Brands of microscopes ............... 44 Subject brightness .................. 25 Optics of the microscope ............ 44 Negative density range .............. 25 Numerical Aperture .................. 47 Gamma ............................... 25 Kinds of lenses' ..................... 48 PHOTOGRAPHIC CHEMISTRY ................ 27 Lens aberrations .................... 49 Developer or reducing agent ......... 27 Combined microscope lens system ..... 50 mFERENCES ............................ 51 Planning Photography Microfossils Robert V. Kesling PHOTOMICROGRAPHY using an optical system This is a concise list of the stages through is a very specialized kind of photography. It which each photograph must proceed. Thought- involves many problems not encountered in the ful and careful planning is required so that each photography of large specimens with an optical stage is adjusted and integrated with the others. camera or microscopic specimens with a scan- OPTICS ning electron microscope. Within the near fut- ure, however, SEM facilities are likely to be In the optical considerations -- the trans- available to only a fortunate few micropaleontol- fer of light from the subject to the film with ac- ogists, and the cost of producing large numbers ceptable clarity -- many factors are interrelat- of photographs will be prohibitive for most bud- ed. The lighting of the subject determines the gets. Commercially designed and produced op- intensity and contrast of the image, as well as tical photomicrography systems are also expen- the portrayal of the essential characteristics of sive, and most of them include features unnec- the subject. The size of the subject and its mag- essary for the particular usage intended. Hence, nification on film determine the size of the film micropaleontologists seem destined for some and the degree of enlargement in printing. The time to planning their own system, utilizing in- focal length of the lens sets the size of the cam- sofar as possible whatever equipment may be era and its support. The optical design and ac- already" -~resent in their organization- or unit. curacv of the lens and the diameter of the open- The following data and photographic "prin- ing the depth of field in the final print. ciples" are presented for use in planning and If all factors are llperfect" we have an accurate, operating a "single-lenstf (usually a coordinated exciting, and even dramatic interpretation of the subject; if all factors are planned and ex- set of lenses cemented together) camera. A few suggestions on films and printing are added ecuted with moderate care, we have an accept- for consideration, although success or failure able picture; but if any one factor is wrong, we in photomicrography centers on the design of have nothing for our efforts except the experi- the camera. ence in what not to do. - In "Photographic Fundamentals" (1961, Light. -- Let us begin the discussion with Course 2320, Extension Course Institute, Air light, since light is the essential denominator in all phases of photography. We are by necessity University, Gunther Air Force Base, Alabama), photography is described (p. 57) as involved with the nature, properties, quality, and behavior of light from the time it bounces ... a process made up of many miracles .... off the subject, makes its way through the lens, the miracle of optics -- how sharp, detailed, and penetrates the film emulsion, until we can brilliant images can be formed by lenses and "see" the final result as a series of light waves projected on a sheet of film .... the miracle radiating from the print. of film, and the latent image *hat is formed on it .... the miracles of chemistry, by which Light has dual sets of characteristics, the latent image becomes a visible one through both taking part in photography. This visible the action of a developer, and then becomes form of energy can act as a radial wave action, permanent through the action of a fixing bath. as in the waves emanating in all directions PAPERS ON PALEONTOLOGY from the subjects we see (like waves spreading specular reflection outward in a pool from the point where a pebble is dropped), or it can act as a quantum, as in the exposure of film during which an amount of light passes through the lens opening during the interval the shutter is open (like the quantity of I mirror I water passing through the spout during the time the spigot is opened). diffused reflection Sunlight contains waves or radiations of all colors in the visible band or spectrum, as well as those longer than the red end (infrared) and those shorter than the violet end (ultravio- let). That is why it is ideal illumination: what- I rough surface I ever the wavelengths to which the film is sen- sitive, they are present in sunlight. Reflections from surfaces. The electric bulb, fluorescent unit, flash, pression that is not lighted. The film is im- or arc light used for artificial illumination has personal; it registers the colors and their in- serious gaps in the spectrum of its light. The tensities as the light energy passes through the human eye is so marvelously accommodating to lens during exposure, impartially and finally. the owner that it is really a poor judge of the colors (or even the accurate intensity) of such With rare and special exceptions, the light; the emulsion on the film is much more paleontologist seeks to portray the form of the discriminating. Before selecting an illuminator fossil and not its color or polish. Therefore, the photographer should check its registration when he photographs, he wants the specimen to on the film with the optical system he plans to give off diffused light. To bring this about, he use. Filters should be added only if they im- usually coats the specimen with a very thin prove the image on the film. layer of sublimated ammonium chloride. The particles are uniform in color (white) and make REFLECTION. When light waves strike the the surface "rough. " As long as the coating is surface of the subject, they may be reflected not thick enough to obscure any structures of or thrown back. If the surface is smooth and the fossil, and its particles are not largeenough polished (like a mirror), the reflected light is to be distinguished in the final print (conveying thrown back at the same angle as the incident a false impression of texture), the ammonium or incoming iight, and the reflection is said to chloride is successful in bringing out the con- be specuZar. But if the surface is rough or ir- figuration of the specimen. regular, the light is reflected in more than one direction and in more than one plane.
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