GEOLOGIC PHOTOGRAPHY 



801 



Serial No. 



Positive 



Or+hochromatic 



Intense Bright Hazy 



Panchromatic 



Super-panchro. 



Full sun, near glare 



Full sun 



Shacie.open sky 



Shade no open sky 



Heavy shade 



Interior 



Dull 



Distance 



Tripod I yes | no 



Stop 



Auxiliar.ylensl 1 |2|3 



Main lens 



35 mm. 

 f/3.5 



Very Dull 



Camera points 

 NW JlL NE 

 W4 o W 



film will add depth of perspective to distant valley and mountain. Finally, in framing 

 the finished print under the enlarger, regard for the rules of pictorial composition 

 and rhythm will yield subtle but sure results. This is not to advocate soft-focus 

 effects, bromoils, or pebble-surfaced paper; the scientist's medium is the needle-sharp 

 ferrotype print from which he should and must not swerve. Nevertheless artistic 

 principles are as much needed in scientific photography as a good voice in a scientific 

 lecturer; there is no merit in nasality nor in poor pictorial composition. 



Color photography is not yet practical for the field geologist. The exposure 

 technique and equipment are simple enough, but the limited advantage of colored 

 field photographs as scientific data does not compensate for their high cost and rela- 

 tively narrow range of usefulness. Furthermore there is comparatively little need 

 for color representation in geologic field photography. 



Darkroom procedure is standard. Tank development with suitable developers 

 and projection printing on glossy paper are recommended. The procedure should be 

 worked out carefully and standardized, both for efficiency and to justifj^ the care 

 exercised in making the field exposure. Pro- 

 jection printing is strongly urged not only 

 because it eliminates the need for large 

 negatives but especiallj^ because it permits 

 a careful selection of the most desirable 

 area of the original film. 



Recording field data and filing negatives 

 are necessary practices. The geologist's 

 notebook will receive the geologic data for 

 each picture; for photographic data a printed 

 form, similar to Fig. 1, which can be filled 

 in largely by check marks, is recommended 

 for its completeness and convenience. Nega- 

 tive filing systems are legion and subject 

 to strong personal preferences; the essential 

 thing is that some adequate system of filing 

 ])e employed. 



Geologic Laboratory Photography. — Pho- 

 tographic technique employed in geologic 

 laboratories is exacting and varied and 

 differs markedly from geologic field photo- 

 graphic technique in that conditions are 

 controllable. Aside from routine work, such as copying and lantern-slide making, 

 geologic laboratory photography falls into two main groups: (1) thin-section photog- 

 raphy through the petrographic microscope, and (2) photography of objects possess- 

 ing surface relief. 



Equipment. — The camera should be a well-constructed "view type" plate camera, 

 from a 31^- by 4i^-in. to a 5- by 7-in. in size, according to the user's preference. A 

 removable lens board, a rising front, a revolving back, and ground-glass focusing are 

 essential. For indoor work, when weight and portability are not of prime importance 

 but accuracj^ is, glass photographic plates will furnish a higher percentage of perfect 

 negatives than any type of film; the cost per unit area is no higher, and breakage of 

 plates troubles only clumsy workers. Plate size will vary with personal preference 

 and with the demands of the work. A convenient device is to employ a 5- by 7-in. 

 camera and plataholders equipped with insert frames to hold 4- by 5-in. plates when 

 desired. Interchangeable lenses are a necessity; the removable lens board is more 

 convenient than a threaded flange and, for megascopic work, possesses sufficient 



Hour 



Filter I I lnlffl 



Time 



Sun shade |yes| no 



f/2.5 



50mm. 50mm. 90mm 



f/3.5 



f/4.0 



Date 



llFieid No. 



135mm 

 f/4.5 



Remarks 



Fig. 1. — Printed form which is useful 

 in quickly checking data taken in the 

 field. 



