CCD size vs. depth of field

[Jeff Donald]

skyy3838, in my obsessing about knowledge, I would like to know why

A nice healthy zoom lens ratio has more to do with it.Anything from 16x and above will do.

is so important to controlling DOF?

Wayne, deep focus is easy to achieve and just about everybody's relatives do achieve it. That is why DOF is so talked about, it's difficult to understand (Laws of Physics) and most people have a difficult time achieving shallow DOF.

[Joe Carney]

>>If I heard as much about composition on some of these boards as I did about shallow DOF,I<<
After watching Tadpole last night. I've been thinking of nothing else other than composition.
The shots were composed well enough througout the movie, I didn't care about DOF, or even notice for that matter. The DP made sure my eyes were always led to the area on the screen I was supposed to be looking at. Composition!!!! Who'd of thought:).

With color enhancement and flattening, it turns out, that was enough. All the shots were deep and the only reason I noticed was because at first I was studying the film. After about 15 minutes, I just sat back and enjoyed it. It may have not looked great on the big screen, but on my large screen TV it looked fine.

So... good lighting, good sound, good compostion, good story, good acting, good cinemetograpy, good editing, dont worry
about DOF.

[Ken Tanaka]

I, too, watched Tadpole tonight and thought it was pretty darn good, especially for its apparently low technical budget. The only distractions to my eyes during the first few minutes were the shaky handheld shots (they should have hired Charles P.) and the color. But I, too, just settled into the story after 15 min.

In my view it is important to understand, but not bemoan, the apparent DOF limitations of small-chip/aperture cameras. Years ago, while working in IT, I would often become frazzled by non-IT people who became frustrated when they realized that the magic of technology could not deliver a specific solution, which they had formulated sans knowledge of technical capabilities, to a problem. If only they had come to IT with their -problem- and not their imaginary solution we could have saved hundreds of meetings and many hours of swordplay.

So it is with any form of imaging technology and story-telling. Framing your visual solutions knowledgably within the context of your capabilities from the start is the most productive and effective path and always has been. Spending many hours in post to create false DOF, as one pro I know recently did, reflects a poor imagination and weak problem-solving skills.

[Dylan Couper]

Regarding composition, I don't think we talk about it much because it's hard to teach/learn the art of composition on a forum.
Agreed, composition is much more important than DOF.

[Wayne Orr]

<<<-- Originally posted by skyy3838 : Shallow DOF can happen with small chip cameras.
I'm sorry,but,while I appreciate what larger chip cams can have to do with shallow DOF,it is not the entire affair.

A nice healthy zoom lens ratio has more to do with it.Anything from 16x and above will do.


Well then, "Skyy" I guess you will be happy to post some frame grabs taken with a mini dv camera that have shallow depth of field. Nothing too spectacular, just a standard head shot done in an interior, similar to shooting an interview in a room, exhibiting narrow depth of field. Please include pertinent information regarding what camera, f-stop, focal length, etc, along with the stills. I look forward to the pictures. Always happy to learn new skills.

[Steve Siegel]

A question for Jeff Donald.

Jeff,
I entered some data into the DOF calculator you posted earlier in this thread: Using XL1-s with a 300mm focal length lens, f/5.6, subject 20 ft away. the DOF calculator said DOF=5 inches for 35mm film. If, as you suggested the DOF for a 1/3 inch CCD is 7.5 times as much, my DOF would be over three feet! My subjects go out of focus if they move a few inches. What exactly do you mean by depth of field...it certainly isn't the region of sharp, or even acceptable, focus.

[Jeff Donald]

It is an error in the DOF calculator. When subject distances are less than 10 times the equivalent focal length (300mm X 7.2 = 2160mm) DOF calculators become unreliable and magnification tables need to be used. I believe that calculator uses a larger Circle of Confusion dimension then would be acceptable for 1/3 inch chips and larger than what might normally be used in determining 35mm DOF.

In your example I get 4 1/4 inches with 35mm film. Because of the extreme magnification we get with 1/3 inch chips the DOF drops to 2 inches. If instead I move back from the subject to 140 ft my DOF is 5 ft 11 1/2 inches.

There is no definitive size for COC. This is why the DOF figures don't work out exactly to the 7.5 times figure also. The generally agreed upon limits are between .033mm to .08mm. The differences in COC is a factor of almost 3 which is why DOF calculators give different readings.

[skyy3838]

<<<-- Originally posted by Dylan Couper : Regarding composition, I don't think we talk about it much because it's hard to teach/learn the art of composition on a forum.
Agreed, composition is much more important than DOF. -->>>

Yes,composition *is* a tough topic for the 'boards because after learning the basics(technically speaking) composition will have more to do with your artistic good sense from there on out.And that can only be dealt with by practice-because theory only gets your foot in the door.And then you ask yourself the tough questions:What sort of feeling about this scene do I wish to convey?Menace,melancholy,madness?How do I make Darth Vader look more towering? High Angle,or real low?Composition is real tricky because a large amount of it depends on the surroundings in which you are shooting.And sometimes,there doesn't seem to be a camcorder with a depth of field large enough to convey what you want to,so,you improvise and hope everything works out,somehow,after all.Are those pair of mountains, not being shot to your satisfaction unreachable by car, foot,zoom lens or different angles, and you don't have the money in the budget to charter a helicopter or plane to get you out for the perfect shot?
Well,that might be a problem that can be somewhat rectified in post,by whatever methods or software are available to you.

In terms of composition,you have to learn to activate your minds
"camera eye" so you can spot the shots that you want to commit.
Watch the movies that have cinematography that you particularly
admire so you can use some of those shots at a later date in your own production,if the context applies.
Remember comic books?Those things are incredibly rich in both storyboards and perpetuity-The producers of "Men in Black","From Hell" and "Road to Perdition" know this all to well,I reckon.

Yeah,compostion.It's pretty much a lifetime study.....

[Don Berube]

Best way to teach newbies composition is a Polaroid camera. It's almost a complete square frame. Instant feedback too, although a bit expensive,,, you could say that the low end digital still cameras are also a good way to study composition. It's definitely a good practice for those who tend to hit the Record button and start recording as soon as they see something in front of them, rather than let the object they are seeing present itself to them before pressing the Record button,,, I always try to look for S-curves in the frame, which can be used effectively to lead the eye of the viewer with a bit of imagination. If someone wants to improve their composition skills, I would also suggest taking drawing and painting classes, along with some art history classes. Many adult continuing education centers offer decent art classes for resonable fees. You don't have to go to a Juliard-level institution to study these things. The key is to start thinking about it more often than you did before, practicing it in a group setting and learning from others is extremely helful in shortening the learning curve. Also, find out what museums exist in your area and become familiar with their schedule and offerings. I love visiting museums and art exhibits whenever I can, the more styles you can expose yourself to, the better. My overall favorite "mentor" to learn from would clearly be Monet. That is an excellent starting point for learning about composition.

- don

[Matt Ockenfels]

Practically, here's the film school skinny on Depth of Field....

For a given focal length, a larger aperture (smaller f/number) provides a smaller DOF; a smaller aperture (larger f/number) provides greater DOF.

For a given focal length AND given aperture, a closer focus (distance to focused subject) provides smaller depth of field and a longer focus provides a longer depth of field.

For a given aperture, a longer focal length (telephoto) will produce a smaller depth of field, and shorter focal length (wide angle) will produce a longer DOF.

So if you are after shorter DOF: (1) Use the largest aperture (smallest f/number) you can, (2) bring the subject close to the camera, and/or (3) shoot telephoto as opposed to wide angle.

As total exposure is a result of both f/stop and exposure time (shutter speed) , changing one means changing the other to maintain correct exposure. If you open the aperture for decreased DOF you will also have to increase the shutter speed. Luckily, if you have an aperture-priority auto exposure, the camera will do this for you!

Cheers,
-Matt Ockenfels

[Jeff Donald]

Matt,

That only works if your image size can vary. Here is an article that discusses DOf and here is a thread also.