Fig. 3. Detail from the geological chart with an arrow pointing to the Lago de Cote.

According to Mr. Vilchez the camera used was an R-M-K 15/23. The lens would have featured a fixed focus and a 6-inch focal length. The shutter speed was 11500 second at f-5.6. The intervallometer was set at 20 seconds between successive exposures.

The film used was black-and-white emulsion with an ASA speed of 80. This fine grain film produces a high resolution negative given a stable film plane and camera and sufficiently fast shutter speed.

The negative was printed on Kodak Safety aerial film, type 3665. The image measured 23 cm X 23 cm (529 square centimeters) while the film base measured 25.3 cm X 23.8 cm. Comparing the image area with the