Photographic Myth Buster #38

#38. The Speed Point for Color Positives (Slides or Transparencies)

True or False?

The speed point exposure for color positive emulsions is located near the midtone exposure for these emulsions.

True.

Unlike the standards for monochrome and color negatives, which place speed point exposures at fractions of a stop above the minimum usable exposures, the standard for color positives (slides or transparencies) has a speed point shift of 3.67 stops that is much larger than that for monochrome and color negatives and a small negative midtone shift of -0.24 stops that leaves the midtone exposure a little to the left of (at slightly smaller exposures than) the speed point exposure.

The diagrams that support the calculation of the standard width of the photosensitive exposure range for various types of photosensitive arrays can be found in the book Photographic Exposure Calculations and Camera Operation.

Copyright 2008 Michael G. Prais, Ph.D.

For a readable but in-depth analysis of this concept along with many other concepts associated with photographic exposure, take a look at the book Photographic Exposure Calculations and Camera Operation. This book provides insight into the equations that govern exposure, exposure meters, photosensitive arrays (both solid-state and emulsion) and the Zone System as well as concepts associated with resolution, dynamic range, and depth of field.

The book is available through Amazon.com (ISBN 978-1-4392-0641-6) where you can Search Inside!™.

Check http://michaelprais.info under Photography for the table of contents, an extensive list of the topics and subtopics covered, the preface describing the purpose of the book, and a diagram central to the concepts in the book.

Should you have any comments or questions about this web site, please contact me. Thanks.

 

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