Depth of Field/Focus Conundrum
I was surprised to see the misstated comments on Depth of Field vs. Depth of Focus in the June 2007 Your Tips get past your editors. To clear things up, here are the definitions of the two phrases from The American Cinematographer Manual (4th edition, 1973, page 625).
- DEPTH OF FIELD - The range of object distance within which objects are in satisfactory sharp focus, the limits being the establishment of a circle of confusion of greatest acceptable size.
- DEPTH OF FOCUS - The range through which the image plane (the emulsion of the film) can be moved backward and forward with respect to the camera lens such as defined under the depth of field and circle of confusion. This term is often confused with depth of field and vice versa.
In common English, Depth of Field is what the photographer is interested in; it is what is in acceptable focus in front of the lens. Depth of Focus is what only a technician is interested in; it is what is in focus behind the rear lens element which the film or image sensor "sees."
More on Field versus Focus
This cute but weird distinction between the terms Depth of Field and Depth of Focus is amusing but terribly in error. As I hope you recognize, Depth of Field refers to the appearance of relative image sharpness in the objects in the scene toward which the lens is pointed. While there are certain generally accepted norms for describing this, there is a lot of room for definition and interpretation.
Contrarily, Depth of Focus refers to characteristics of the projected image inside the camera at the location of the film or digital sensor.
Robert L. Pfeiff, MFA
Retired Professor of Photography (Rochester Institute of Technology and Banff School of Fine Arts)
Thank you to Robert, Kerry and the few others who wrote in to correct our statement. We certainly have every intention of printing the proper technical explanations as clearly and concisely as possible, and regret those times that we slip up, often with great embarrassment when an error sneaks through. We do appreciate the fact that our loyal readers love to contact us and tell us when we've erred, or when we've made your day a good one! We take all comments seriously and read all letters and emails, even those that never make print.
- The Editors
Oscars on Video?
I have been a filmmaker since the late '60s and am now working in the video field. I now shoot almost exclusively on videotape. I entered some films in the Academy Awards competition back in the late '70s and remember that we all had to adhere to a strict set of rules, one of which was that my production had to be originated on film and projected in a theatre in Los Angeles County for seven consecutive paid play dates, on film, not videotape. This was no easy task if you could not afford a 16mm to 35mm blowup.
At the risk of appearing a bit uninformed, I must ask if you could tell me when these rules changed and to what extent they have changed. Obviously, I can originate on tape now, but can I also project from tape or DVD?
Richard Mangan Whitefish Bay, WI
As a matter of fact, Richard, the rules have changed. One change is the format in which the original source is recorded. We attended this year's Academy Awards Documentary nominations, and all of the nominated documentaries were shot on video, using relatively affordable consumer or higher-end prosumer gear. They were then bumped up to acceptable formats and edited, using highly-professional software. See our Oscar report in our vidcast, Videomaker Presents, at www.videomaker.com/vidcast/55.
Although we had a special screening, at the time of the report, several of the nominated docs weren't available to the general public, because one of several rules that exist is that the movie has to be seen in a traditional movie venue, not on TV, during a very specific time, before the nomination. We certainly don't profess to know all the changes that have taken place, but to learn more about the Academy Awards and the rules, go to www.oscars.org/80academyawards/rules/rule12.html.
- The Editors
Video on the Cheap
Hi, I have been a subscriber to your magazine for a long time and it has been a great experience all these years. I would like to see articles about people who are doing business using consumer camcorders: cameras than don't cost more than $600.00 at least. I know that today's equipment has been lowered in terms of costs, and you can practically have your own production studio with a good computer and a good camera, but what about people who can't afford more than a regular camcorder and a turnkey computer system?
Csar D. Daz
Your wish is our command, Csar. Next month's Basic Training column will have an article on Low Budget Big Bang productions, followed by a Sound Advice column on Bargain Basement audio in the October issue. Stay tuned!
- The Editors