Further Information on Focus

This site offers the following additional information on focus-related matters:

"Depth of Field Revisited" (in HTML format) provides an quick overview of the method described in The INs and OUTs of FOCUS .  

A really neat conventional depth of field calculator exists on line as Nick Sushkin's Depth of Field On-Line Plotter. This on-line calculator lets you enter the focal length and several apertures for your lens, and receive back a plot of depth of field over a range of distances. Originally Nick fixed the diameter of the circle of confusion at 1/30 mm, but he's recently updated his calculator to let the user enter any value. The formulae Nick uses are superior to what one generally finds in books; they are accurate in the close-up region without having to compensate for effective f-number!

The Acrobat Reader needed to wiew and print the the following PDF documents can be downloaded from the Adobe Web Site. We continue to recommend Acrobat Reader 2.1: if nothing else it's faster on both Mac and PC machines than Acrobat 3. This is especially important if one has an older, slower computer.

An Addendum to FOCUSING the VIEW CAMERA   describes basic information about view camera principles, especially depth of field. The PDF file FVCADNDM.pdf is about 163k in size and carries the full detail of the original printed Addendum.

A two-part article on View Camera Focus and Depth of Field appeared in VIEW CAMERA magazine in July/August and September/October 1996:

• VCFaDOF1.pdf (341k) covers the Scheimpflug Rule and the Hinge Rule.

These ten articles are essentially reprints of articles on the subjects of focus, depth of field and lenses published by SHUTTERBUG    Magazine between October 1991 and December 1993:

• SHBG01.pdf (85k), "Adjusting Depth of Field", Shutterbug   Vol 20 No. 12, October 1991. This article challenges some of the standard notions about depth of field.
  
  
• SHBG02.pdf (84k), "Adjusting Depth of Field Part II", Shutterbug   Vol 21 No. 7, May 1992. This item suggests it may sometimes be the best strategy simply to focus at infinity.
  
  
• SHBG03.pdf (52k), "Adjusting Depth of Field Part III", Shutterbug   Vol 21 No. 8, June 1992. Explains how to estimate how out-of-focus an object might appear.
  
  
• SHBG04.pdf (138k), "Adjusting Depth of Field Part IV", Shutterbug   Vol 21 No. 9, July 1992. A summary of the subject-oriented view of depth of field, and doing it without a calculator.
  
  
• The above four articles are also available on the web in Russian, beginning at http://hiero.ru/article.php?id=adjusting_dof
  
  
• SHBG05.pdf (16k), "The Scheimpflug Principle - Part I", Shutterbug   Vol 22 No. 1, November 1992. An introduction to the well-known Scheimpflug Principle.
  
  
• SHBG06.pdf (151k), "The Scheimpflug Principle Part II", Shutterbug   Vol 22 No. 3, January 1993. Every lens is a zoom lens: focal length may change when you tilt your lens!
  
  
• SHBG07.pdf (153k), "The Scheimpflug Principle Part III", Shutterbug   Vol 22 No. 4, February 1993. This article is really about perspective and distortion - a subject not (yet) covered in Harold's books!
  
  
• SHBG08.pdf (150k), "The Scheimpflug Principle Part IV", Shutterbug   Vol 22 No. 5, March 1993. The Hinge Rule and how the Hinge Rule and Scheimpflug Principle interact.
  
  
• SHBG09.pdf (122k), "Depth of Field for View Cameras Part I", Shutterbug   Vol 23 No. 1, November 1993. How conventional depth of field works for view cameras.
  
  
• SHBG10.pdf (37k), "Depth of Field for View Cameras Part II", Shutterbug   Vol 23 No. 2, December 1993. Applying the subject-oriented depth of field philosophy to view cameras, and how things can get so out of focus with a view camera that they seem (mathematically) to be behind the camera!

From Photo Techniques magazine:

• ATVB.pdf (332k), "A Technical View of Bokeh," describes what makes the out-of-focus images different for different lenses. Originally published in the May/June 1997 issue.

Copyright Notice

The contents of the above portable document format files (or printed versions thereof) are copyright Harold M. Merklinger of Halifax, Nova Scotia, Canada. With appropriate attribution, either to "Harold M. Merklinger" or to "http://fox.nstn.ca/~hmmerk/", personal or not-for-profit use may be made of these materials. That is, providing individuals or organizations acknowledge the source of the information and do not charge for its use or distribution, they may copy and use the materials provided. Without the express permission of the author, the material may not be used in or included with printed or formatted-for-computer records offered for sale. Individual photographers, professional or amateur, are free to make personal use of this information in their work. Information on how to contact the author is provided at How to get these books.


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