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Old April 23rd, 2003, 03:25 AM   #46
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Check this out

Go to the site below and once there click on the GL. Next click on the view 360 info. Next, click on documents and after that opens, click on the .pdf and scroll down to page 5. It shows a picture of a couple in focus and the background soft. I think this shows what Jason is trying to achieve.

www.canondv.com
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Old April 23rd, 2003, 06:06 AM   #47
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Yup, the images are meant to highlight the AV (aperture priority) mode. Notice that they are at a marina, and there are no objects in the background for some distance. That would require a technique similar to what I describe. If you focused on the people, you will achieve some pretty incredible DOF and the boats in the background might be in focus.

Working with DOF is a sophisticated regimen, just like lighting, composition and art direction. It's not easily mastered and requires the right tools. The techniques do not work in all situations. A run and gun production is not ideal for a methodical approach to DOF. It requires a tape measure or optical distance finder, DOF Chart or PDA with DOF program, and an external monitor. The external monitor, though not required, makes checking DOF much easier (especially if your lens lacks a distance scale).

Once you have the required tools assembled, it's just a matter of plugging in the aperture, focal length of lens, and different camera to subject distances to learn the DOF limits. Then place your subject at the limits of the DOF. The closer you set focus, the shallower the DOF. Read the article to understand how changing focal length and distance to subject can cancel each other out (Law of Reciprocity).

This work method is best used on a set where you have greater control of lighting and other important elements. It requires a slow, methodical approach to your work. Again, it's not a method for run and gun or ENG type production.
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Old April 23rd, 2003, 09:21 AM   #48
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you guys are coming out of everywhere. Wayne, your absolutely right. It is near impossible to get results indoors. I was trying everything last night at home with a big bluesitup ball about 10 feet away from me and the background around 10 feet behind it. I tried using everyones tricks on here. Im going to give it another go this eve. But probably end up doing it in post if i cant figure it out. Guess it goes with the first thing i read in this forum "shoot, shoot and reshoot!".

Thanks for all the pro-tips guys!
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Old April 23rd, 2003, 10:02 AM   #49
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I have read the article in DVinfo which clearly states that zooming in will not affect DoF as it cancels out the net effect. The only way is to open up the aperture.

But a website suggested from previous posts, http://www.dvcreators.net/media/depthoffield.html suggested that we zoom in as much as possible to get shallow DoF.

Are they mistaken?
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Old April 23rd, 2003, 10:38 AM   #50
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It depends on how important the object size is. In their examples, notice how the size of the persons head increases in size. If you can work with your subject size being larger, then changing the focal length will decrease DOF. If the subject size must remain the same size (News Anchors head size) then zooming in (decreasing DOF) will be offset by changing distance to subject. The key is if the subject must remain the same size or not.

DV Creators is correct in a limited way. They do not explain the consequences of changing subject size and the Law of Reciprocity. They are repeating the same misconceptions most people have with DOF.
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Old April 23rd, 2003, 10:38 AM   #51
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Hi Michael,

<< I have read the article in DVinfo which clearly states that zooming in will not affect DoF as it cancels out the net effect. >>

Actually that's not what it says... it really reads like this: "If you zoom in without moving the camera back, then DoF will decrease."

In other words, the DV Creators tutorial is sort of correct, but the problem with that technique is -- as Jeff states in his article on our site -- that you're now changing the relative size of the object you're shooting... which is going to look weird unless you're shooting the entire production this way (otherwise the resultant change in object size is really going to stand out).

Hope this helps,
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Old April 23rd, 2003, 10:50 AM   #52
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Depth of Field

Thanks to Chris Hurd bailing me out of my computer illiteracy, I can post this photo. It's a still from a video clip I shot on my XL-1s. I shot it in manual exposure (F2.8, or 3.6, I forget which), manual focus, frame mode using a 1/2 black promist filter. Great, afternoon low-angle light helped get this look.

http://www.dvinfo.net/media/Image0.jpg
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Old April 23rd, 2003, 10:55 AM   #53
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Indeed, the picture (from the Canon site) portrays what Jason is trying to achieve, but sorry guys, that picture just does not cut it. A high shutter setting is being used, probably at least 1,000 of a second or higher. This will result in a narrower depth of field than a normal shutter setting of 1/60, but will also result in motion jerkiness that is simply not acceptable for normal shooting situations. It also requires a tremendous amount of light to achieve, way beyond the usual interior lighting set-up. And again, the background is a considerable distance from subjects and camera. Actually, the effect in this picture could have been heightened even more by using a longer focal length. As long as the people in frame don't move, the high shutter speed will not be objectionable. High speed shutter has been used quite effectively in movies such as "Saving Private Ryan" and "Gladiator" to add a "special look to" scenes of battle.

Michael, regardless of what format you shoot with, be it 35mm motion picture film, 16mm, 2/3" chips or 1/3" chips, depth of field is a result of focal length and aperature (iris). The basic rule is: the longer the focal length and/or the wider the aperature (lower numbers, eg f/1.6), the narrower the depth of field. The shorter the focal length and/or the narrower the aperature (higher numbers, eg f/16), the greater the depth of field. This is true for all formats, bearing in mind that larger image surfaces, such as 35mm will yield narrower depth of field, and smaller image surfaces will yield much greater depth of field, but the predeeding rule still applys. This is physics and cannot be ignored. So the narrowest depth of field any given format is capable of, will be found using the widest aperature at the longest focal length. This can be confirmed using the Panavision depth of field guide I mentioned above. (Be wary: zoom lenses seldom perform optimally at their longest focal length at widest aperature)

Charles lovely picture is an example of long focal length and wide aperature equals narrow depth of field. But what it teaches budding filmmakers is never shoot an actor with a head bigger than a duck.
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Old April 23rd, 2003, 11:07 AM   #54
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Wayne... "the picture (from the Canon site)" -- I'm trying to get away from it being known as a Canon site; it's actually an "everything site" now, with some Sony stuff up there too, and JVC and Panasonic material forthcoming. If you have anything that's non-Canon that you'd like to contribute, I'd warmly welcome it!

Any other DoF image examples, anybody?
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Old April 23rd, 2003, 11:32 AM   #55
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<<<-- Originally posted by Chris Hurd : Wayne... "the picture (from the Canon site)" -- I'm trying to get away from it being known as a Canon site; it's actually an "everything site" now, with some Sony stuff up there too, and JVC and Panasonic material forthcoming. -->>>

I think there is some confusion Chris. I was referring to the link in James Emory's post, www.canondv.com. If that isn't the Canon website, I must be having an halucination. Which would not be all that unusual.
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Old April 23rd, 2003, 11:43 AM   #56
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DOF's just ducky

Wayne:

It's a goose. Goosies go: "honk, honk."

Duckies go: "Aflac."
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Old April 23rd, 2003, 11:46 AM   #57
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Wayne -- thanks for the clarification, looks like the confusion was all mine, hallucenogenics aside.... that's what I get for not following the thread as closely as I should.
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Old April 23rd, 2003, 01:55 PM   #58
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Just to reinforce just how "deep" DOF on a 1/3" camera can be...

I was recently making some test shots in which I was trying to shoot a close subject while keeping a local landmark, visible through a window, in identifiable focus. I tried a wide variety of exposure and subject lighting combinations, 22 all told. In the end, the landmark remained easily identifiable and only a few shots markedly blurred it. The landmark was over 1 (straight-line) mile away.

Perhaps the best way to envision the effect of aperture on DOF is to try the poor-man's glasses trick, particularly if you're near-sighted. Curl your index finger until there's only a tiny opening. Then peer through it and adjust the opening until you can see some object clearly. As you widen the opening the object blurs. That's basically what's happening in the camera with respect to the iris.
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Old April 23rd, 2003, 06:04 PM   #59
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I dont wish to be argumentative but I would like to dispel the notion that DOF has anything to do with CCD size - it does not

The Three Factors which affect DOF are

1 Focal Length
2 Aperture - f-stop
3 Camera to Subject distance

CCD size will introduce telephoto compression effects which enter play for smaller CCDs

http://www.8mm.filmshooting.com/community/articles/dof.php

has an article which should be read since it is an extract from Ilford Manual of Photography, 4th Edition, 1949. Pages 14 to 17

Also for shallow DOF effect you should be aware that Circle of Confusion extends one third in front of subject focal plane and two thirds behind subject focal plane

so using this for the background blur effect you need - arrange your camera to subject distance to be approx 1/4 (or less) of the distance of the camera to the background. Then the aperture will act as a background blur control (small f number - more blur)

hope this helps
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Old April 23rd, 2003, 07:07 PM   #60
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John

http://www.8mm.filmshooting.com/

Fascinating site -- thanks for the link,
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