film speed calculator slide chart
Date: copyright 1966
Inventory Number: 2004-1-0377
Classification: Slide Rule
Dimensions:25.4 × 7.9 × 4 cm (10 × 3 1/8 × 1 9/16 in.)
DescriptionRectangular sleeve composed of two paper rectangles, joined by six brass fasteners, containing a paper slide. The slide chart and slide are printed in black, yellow, and red on white.
Near the left edge of the face of the slide chart is a rectangular slot through which the slide is visible. Printed along the left edge of the slot is a scale for "RELATIVE LOG E (Positive Number)", carrying values from .00 to .99. Printed along the right edge of the slot is a scale for "RELATIVE LOG E (Negative Number)", with values ranging from -.00 and -.99 to -.01. Printed on the slide along the left and right edges of the slot are scales for "ABSOLUTE LOG E". Both have values descending from .99 to .00.
Four additional, much smaller slots have been punched through the right-hand side of the face of the chart. Near the top these are labeled "FILM / EXPOSURE / VALUE" (leftmost, above slot), "MCS" (leftmost, below slot), and "FILM / SPEED / VALUE" (rightmost, above slot), "1/E" (rightmost, below slot). The two slots near the bottom of the chart's face are identically labeled. Through each slot a single value, printed on the slide, is visible.
Printed on the top half of the back of the slide chart are instructions for the chart's use, as well as two example problems. Below are tables of "CONVERSION FACTORS" (center) and "SOME COMMON SPEED CRITERIA". The Itek trademark is printed near the bottom of the back of the slide chart.