Reading Film and Video Makers

DEPTH OF FIELD

By Andy Jones.

A friend of mine was completing a video drama course, and the brief of his last project was that it had to be 'cinematic'. He had a camera that had several presents in its gamma curve (that could be totally tweaked and changed). A few of the presets were 'cine-gamma' that added a film-like richness to the colours. He was also shooting in 25 frames-per-second progressive scan. The results of his test shoots were very film-like in terms of colour and motion, but something was missing.

The thing that was missing was the shallow depth of field (which for ease, I'll shorten to DOF) - everything had that 'all in focus', camcorder look. While certain filmmaking genius, like Orson Wells, mastered a 'universal focus' look, most motion pictures go for the shallow DOF look.

So how do you achieve that look? Is it really possible on a 1/3-inch CCD camcorder? I've heard an awful lot about DOF from various people, and it's usually very mistaken. After a series of experiments with short films, I've decided to layout my view on how DOF works, regardless of the camera your using. (Just as long as your camera has a manual focus ring…)

DOF is influenced by three factors: closeness to subject, focal length of lens, and aperture setting.

Simply put, the factors work like this:

SHALLOWER DOF -------- DEEPER DOF
Close to subject -------------- Far away from subject
Telephoto Lens -------------- Wide-Angle Lens
Open Aperture --------------- Smaller aperture

So: to maximise the area that's in focus (to get the most deep DOF), use a wider-angle on your lens, and stop down the iris as much as you can, and back away from the subject.

To minimise the DOF (to get the shallowest focus possible): zoom in as far as you can, get as close to the subject as you can, and open the iris up as much as possible.

With a camera like the DVX100, the VX2000, etc, your optical possibilities for shallow DOF are quite limited: the maximum telephoto for these types of camcorders is only usually between 45mm - 65mm. Longer lenses are the number one factor in getting the shallow-DOF look. 35mm cameras usually use a lens in the range of 25-250mm, the DVX is only 4.5-45mm, and wider-angles (shorter focal lengths) exaggerate the effect of everything being in focus. So the DVX (The camera my friend was using) has a major strike against it.

You can cheat in a number of ways. First and foremost, get your subject as far away from the background as possible. The further they are from the background, the more the background will be out of focus.

Second, you can get a close-up lens like the Century Achromatic Diopter. That lets you focus closer, so you can get the camera closer, and closer to subject = shallower DOF.

Third, you can use a telephoto adapter like the Century 1.6x. That'll extend your telephoto range to 72mm, giving a shallower DOF look.

Fourth, depending on what camera you've got, you can use a product like the Mini35 (an adapter for the VX1/2000, PD150, XL1/2 or DVX100) to give you results that are simply not possible in-camera alone. This amazing piece of kit allows you to mount any professional 35mm motion picture camera lens on it (Zeiss primes, Panaflex, etc) You can achieve amazing shallow DOF looks with those products, but it costs £6,000 for the adapter itself and an awful lot more for the pro lenses!!

So, to reiterate: for the shallow DOF look, do these in the following order:
1. Zoom in as far as you can. If you can't zoom in all the way to the maximum your camera allows, try backing up some so that you can continue zooming in. Max telephoto is the most important factor.

2. Open the iris as much as possible. If that means using the ND filters, use 'em. Get that iris as close to "open" as you can.

3. Position your subject to be as far away from the background as possible. You cannot underestimate how important that is. If it means changing your shot or composition, change it. Move your subject across the street if you can -- it'll make all the difference.

4. Get as close as you can. Proximity counts for a lot. Use a close-focus diopter if you must.

I hear a great deal of myths about DOF in camcorders. After a long chat with one of my old lecturers, a chap called Gordon, who worked for Panavision many years ago, I'm going to try my best to dispel these myths:

Myth 1: "imaging size affects DOF, larger imagers = shallower DOF". False. The imaging size has nothing to do with the depth of field. The imager size (whether larger like 35mm film, 16mm film or 2/3" CCD's, or small like 1/6" CCD's) affects the FIELD OF VIEW, but not the DEPTH OF FIELD. And larger imagers require longer lenses to deliver usable fields of view. Smaller imagers require shorter lenses. A 35mm camera uses 25-250mm for a zoom, a 1/6" CCD camera might use 2.5-25mm. So the 35mm camera gets its shallower DOF from its longer lenses, not from its imager size.

Myth 2: "focal length is irrelevant in DOF. To use telephoto, you have to back up (which increases DOF). To get close, you have to use wide-angle (which increases DOF). They cancel each other out." No they don't. I mean, yes, technically they do, but just try it, look at your shots and you'll see, the telephoto shot clearly, clearly looks like the background is more out of focus. Whether it's technically as "in-focus" or not is irrelevant, the telephoto lens delivers the optical illusion that the background is more out of focus, and that's what we want: the APPEARANCE that the background is out of focus. For comparison, reference these shots:

Both were shot by my friend with the DVX100 at identical aperture (f/2.8 ) and in the wide shot, he moved as close as possible and focused as close as possible to minimize DOF. On the Tele shot he zoomed in as far as possible, then got as close as he could (while maintaining the same image size). Depending on the quality of the printout of the magazine, Hopefully you can see that the telephoto shot, while maintaining the same aperture and the same image size, looks like it has much shallower DOF.

Back to Top