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depth of focus

oakstreetphotovideo

oakstreetphotovideo

Ok, I come from a technical / physics / lens theory background and depth of focus has always had the definition contained in this Wiki entry, to me. The term is useful to people designing cameras, image sensors, lenses, etc., but not to shooters; the way I understand/use it.

So here is the dilemma. I am in the middle of "The Digital Filmmaking Handbook", and the author uses the term "depth of focus" to mean the specific distance (focal plane to subject) for which the lens is focused. At least, that is what I have determined from the context; he doesn't actually define the term, nor is it defined in the book's glossary. He definitely isn't using the term as I understand it. In the other book I finished recently (Shut Up and Shoot), the author uses depth of focus synonymously with depth of field. (I should also warn anyone reading these books that they are full of technical errors. I really wish these authors would stick to things they understand.)

Given that I don't read too many of the filmmaker books, nor do I spend a lot of time networking with real cinematographers, I'd like to know what the term "depth of focus" means to DPs in general. Is this just one of those overloaded terms that has a different meaning in the filmmaking industry than it does in science?

Doug
 
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I'm not a DP, but in your first example, it should be "focal distance".

Depth of focus could be a synonym for depth of field, but as per that wiki entry, depth of focus true meaning is the distance from lens to film plane, which is really a VERY technical area, because basically since lens mounts are standard, the only time you would ever have to know that term is if you are using an adapter or other device that might affect the distance the rear element of the lens is pushed away from the film plane, so that you can properly pull focus as marked on the lens.
 
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Thanks, Wideshot. I'm not confused about the real meaning of "depth of focus", but I was beginning to wonder if it had a 2nd meaning. I'm very happy with "focal distance". I'll be sure to use that term, as I think it is clear and concise.

I am losing faith in these authors, though. I wonder how knowledgeable these people are in the areas where I may not know better. To cite a typical example that rather upset me some years back regarding a C++ programming text written by an academic who bragged that his wife learned the language with him and helped him edit the book. That was a text I was given for a college course I was teaching. At that time, I had written over 500,000 lines of production C++ program code (that would be code that had gone into commercial products). The book was full of errors, so I instructed my students that when the book disagreed with me, that I was right and the book was wrong. I pointed them at the forward, and the authors admission that he spent 3 months learning the language, and contrasted that to my 15 years of professional experience.

I hate clueless authors.

I'd apologize for the rant, but I would think it's Ok to hijack my own thread. :P

Thanks, again.

Doug
 
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No, I think its really a case where your knowledge and experience is leading you to having intuition that you know better or could do it better or when they make a mistake, that you can point it out.

In certain areas, you no longer need to read books (like digital camera operation), which means you should try taking it to the 200 or 300 level stuff. Soon enough, you'll only read 400 level stuff from the masters.

But the in-between stage is the re-enforcing of the knowledge with practical usage, followed by pushing the envelope, which leads to wanting to read more in-depth technique.

In other words, go shoot something amazing, put it into a short, and enter it into SLIFF 2008 for free! :)
 
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In other words, go shoot something amazing, put it into a short, and enter it into SLIFF 2008 for free!
Click to expand...
I'm not a good coordinator, so I generally shoot for other people, except when I'm practicing technique or testing equipment. :( I'm working with a producer now on a movie we're hoping to shoot in October; too late for SLIFF. Furthermore, I'll just be that guy in the small print under "Director of Photography". Actually, I might be stuck directing this one, in addition to being DP and camera operator, because they haven't found a director, yet. That really frightens me.

Doug
 
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p.s. I'll read just about any book, because there is always something there for me to learn. It worries me, however, when the author is covering one of those narrow areas where I have some authoritative knowledge and they get it wrong. I'm a specialist, so there are many many things I don't know about making movies. If I could latch onto a good producer, I'd stick with lighting, camera, and a little post production. I'd rather not learn the details of the 3,274 other jobs.
 
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OS, When it gets to the point where you're required to shoot/direct that piece, give a call, I'll help talk you through the steps. This 48 hour, we developed a list of things that has to happen to make the shoot go right and get what we need in camera.

On topic, I've found lots of "technical" resources that don't know the difference between focal length, focal distance and DoF. It is frustrating, especially when you're just getting started on this stuff.
 
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Thanks, Knightly. I'm still holding out hope that Gina will find a director. She wrote the screenplay, she is producing the movie, and she is playing the lead role. She has suggested that she could also direct, but I'd rather direct from behind the camera than have her directing when she is in the scene. She's a bit of a control freek, so it is hard to convince her that finding a qualified director will help, not hurt her vision. I've been using Clive's advice about writer-directors, although it may not apply to writer-director-actors. :) It's a reasonably long and complicated shoot. I'm concerned that if Gina doesn't delegate some of the important roles, the movie will die under it's own weight. I believe in the project enough to put my weight behind it, and I'd be happy to take on a directorial role, but I really don't have any experience in that area, so it would be foolhardy for me to just step in and take over that role.

Thanks again. The schedule hasn't been set, but we're looking at October 08 as a rough target. I would not be surprised if it gets pushed into 2009.
 
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