#7. Bellows (short-distance) Corrections
True or False?
Bellows (short-distance) corrections are inappropriate when using a lens capable of three-dimensional metering.
The bellows or short distance correction to exposure that is needed in macro or short-distance photography is calculated with the same expression, (1 – f/us)2 that is used by three-dimensional exposure metering in its calculation of exposure corrected for the distance to the subject, us, and focal length, f. Since a three-dimensional exposure metering already incorporates a distance correction in its calculation of the correct camera settings for a midtone exposure, it is inappropriate to manually include it a second time.
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.