# Photographic Myth Busters

True or False?

These true or false questions have been developed around many of the misconceptions about exposure and exposure meters that photographers have taken for granted. These questions are being asked in on-line discussions to encourage photographers to think about their answers. Answers to the questions along with any useful responses are added shortly after they are posted on-line.

A readable but in-depth analysis of these concepts along with many other concepts associated with photographic exposure are available in my 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), the Zone System, resolution, dynamic range, and depth of field.

The book is available through on Amazon.com where you can Search Inside!™. The table of contents and an extensive list of the topics and subtopics covered are also available under Photography on this web site.

Group A

#1. Shutter Speed
The shutter speed for an exposure time setting of 1/125 seconds is 125. [True (p34)]

#2. Sunny f/16 Rule
According to the Sunny f/16 Rule, a photographer should use an f/16 aperture setting and the shutter speed that is closest to the value of her film speed (the photosensitivity) for proper exposure. So, when using an ISO 100 photosensitivity setting, a photographer should use a shutter speed of 125 on traditional cameras with whole-stop settings but a shutter speed of 100 on modern cameras with fractional-stop settings because ISO 100 is an available setting on modern cameras. [False (p120)]

#3. The Midtone Reflectance for the Sunny f/16 Rule
The Sunny f/16 Rule uses a midtone reflectance that is less than 18%. [True. It uses 14%. (p144)]

Ansel Adams’ zones are defined by the whole-stop settings of traditional cameras and cannot be used with fractional-stop settings of modern cameras. [False (p193)]

#5. Focusing Distance
Your focusing distance is approximately one-third the way between the front and back of your depth of field (more accurately, field of focus). [False. It varies uniformly between zero and half way. (p295)]

#6. Resolution and Depth of Field
The spatial resolution of a camera system (lens, photosensitive array, and supports) determines the field of focus and its depth of field through the diameter of confusion. [True (p299)]

#7. Bellows (short-distance) Corrections
Bellows (short-distance) corrections are inappropriate when using a lens capable of three-dimensional metering. [True. Three-dimensional metering includes the bellows correction. (p28)]

#8. Shutter Speed and f/Number
A one-stop increase in the shutter speed and a one-stop increase in the aperture number (the f/number) both decrease the quantity of light reaching a photosensitive array. [True (p35)]

#9. The Effective Aperture Number
The effective aperture number A(1 + m), where A is the aperture number and m is the magnification, is an unwarranted and ineffective attempt to replace the quantity A/(1 – f/u) in the exposure equation with the quantity A(1 + m). [True (p257)]

#10. DX-coded Film Canisters
The maximum emulsion (film) speed available in a DX-coded film canister is ISO 5000. [True (p88)]

Group B

#11. Photosensitivity (Film Speed) and 18%
ISO/ANSI sensitometric (film speed) standards use 18% reflectance to define the photosensitivity (film speed) for emulsions. [False (p147)]

#12. Exposure Meters and 18%
Exposure meters are calibrated to 18% reflectance by the ISO/ANSI standards for exposure meters. [False (p143-5)]

#13. Photographing an 18% Reflectance (Gray) Card
The result of metering and photographing an 18% reflectance (gray) card is an image with that card appearing at 18% gray. [False (p148)]

#14. Exposure Meters Measure Illuminance
All exposure meters measure illuminance. [True (p135)]

#15. Incident-light Exposure Meters
Incident-light exposure meters assume that scenes have a 3% midtone reflectance, and they match that scenic midtone to the photosensitive midtone of the photosensitive array in use. [True (p153)]

#16. Reflected-light Exposure Meters
Reflected-light exposure meters assume nothing about the exposure range of a scene, and they simply match the calculated representative midtone of the scene to the photosensitive midtone of the photosensitive array in use. [True (p158)]

#17. The Accuracy of Reflected-light Exposure Meters
Reflected-light exposure meters are often inaccurate because they can be “fooled” by excessive highlights or shadows in a metered scene. [False (p151 and p158)]

#18. The Accuracy of Incident-light Exposure Meters
Incident-light exposure meters are more often accurate because they are not “fooled” by excessive highlights or shadows in a scene. [False (p151 and p158)]

#19. Assumptions and Accuracy of Incident-light Exposure Meters
Incident light exposure meters assume nothing about the scene and are, thus, more accurate. [False (p151 and p158)]

#20. Assumptions and Accuracy of Reflected-light Exposure Meters
Reflected light exposure meters tell the photographer more about the scene and are, thus, more accurate. [True (p151 and p158)]

#21. Hand-held Exposure Meters
Hand-held exposure meters are more accurate than exposure meters found in modern cameras. [False. Standard do not require reporting and manufacturers do not offer statistical measures of accuracy which would allow comparisons.]

Group C

#22. The Reference Exposure
The reference exposure Ho, which appears as the numerator in the definition of the photosensitivity (film speed) in terms of the speed point exposure Hsp, S = Ho / Hsp, is the speed point exposure for ISO 1, that is, for a photosensitivity of one. [True (p148)]

#23. The Midtone Exposure
The midtone exposure of an exposure range is determined by the minimum usable exposure and the maximum usable exposure of the range. [True (p55)]

#24. The Photosensitivity (Film Speed) and the Midtone Exposure
The photosensitivity S, which is usually calculated from the speed point exposure Hsp through the equation S = Ho / Hsp, is independent of the midtone exposure. [False (p55)]

#25. Determining the Photosensitivity (Film Speed)
The photosensitivity (film speed) of a photosensitive array is most accurately determined from the minimum usable exposure and the maximum usable exposure of the array. [True (p55)]

#26. The Midtone Exposure and the Photosensitivity (Film Speed)
The midtone exposure of any emulsion or solid-state media determines its photosensitivity (film speed). [True (p54)]

#27. The ISO Equivalent Setting for Raw Data
The ISO Equivalent (photosensitivity) setting on a camera is extraneous when processing “raw” exposure data. [True (p71)]

#28. Exposure Meters Point to Midtone
Modern exposure meters point to the midtone exposure of the photosensitive exposure range of the emulsion or solid-state photosensitive array in use. [True (p138)]

#29. Midtone Exposure, Photosensitivity, and Exposure Meters
The direct connection between the midtone exposure and the photosensitivity allows photographers to use any type or speed of emulsion in their (emulsion) cameras. [True (p138)]

#30. The Actual Width of a Photosensitive Exposure Range
The actual width of a photosensitive exposure range is determined by the minimum usable exposure and the maximum usable exposure of the range. [True (p56)]

#31. The Standard Width of a Photosensitive Exposure Range
The standard width of a photosensitive exposure range for a photosensitive array can be calculated from the reference exposure Ho, which is found in the definition of the photosensitivity S = Ho / Hsp, and the location of the speed point exposure Hsp relative to the location of the minimum usable exposure Hmin. [True (p57)]

#32. 18% Midtone Reflectance
Eighteen percent reflectance is the midpoint of a five-stop exposure range. [True (p145)]

#33. Midtone Reflectance of the Zone System
The nine-stop (nine-zone) photosensitive exposure range used by Ansel Adams for his Zone System has a midtone reflectance of 4.4%. [True (p155)]

#34. The Midtone Reflectance of Jones and Condit
In the 1940s, Jones and Condit found that the “typical” exposure range for the scenes that they examined had a contrast ratio (a maximum to minimum exposure ratio) of 160:1 and an 18% midtone reflectance. [False (p151)]

#35. Exposure Range for Monochrome Negatives
The standard width of the photosensitive exposure range for monochrome negative emulsions is 7.5 stops. [True (p61)]

#36. Exposure Range for Color Negatives
The standard width of the photosensitive exposure range for color negative emulsions is 6.2 stops. [True (p61)]

#37. Exposure Range for Color Positives (Slides or Transparencies)
The standard width of the photosensitive exposure range for color positives (slides or transparencies) is greater than the standard width of the photosensitive exposure range for monochrome negative emulsions. [False (p61)]

#38. The Speed Point for Color Positives (Slides or Transparencies)
The speed point exposure for color positive emulsions is located near the midtone exposure for these emulsions. [True (p61)]

#39. Exposure Range of ISO Equivalents
An ISO Equivalent setting on a “digital” camera points to the midtone exposure of eight-stop photosensitive exposure range of the integral solid-state photosensitive array. [True (p61)]

#40. The Standard Photosensitive Exposure Range of ISO Equivalents
The standard width of the photosensitive exposure range for a solid-state photosensitive array is less than the actual width of the photosensitive exposure range for ISO Equivalent photosensitivities. [True (p61)]

#41. Photosensitivity (Film Speed) and Midtone Exposure
The photosensitivity (film speed) of an emulsion or a solid-state photosensitive array points to the midtone exposure of the photosensitive range of the array. [[True (p54 and p56)]

Copyright 2008 Michael G. Prais, Ph.D.