XF100: Setup suggestions for Interview (DOF)

[Bob Leeds]

The documentary project I'm now working on involves doing standard interviews of subjects indoors. I already have an XF100, so that's what I'm going to use. I also have a 750 watt Rifa Softbox as well as an Ikan Multi-K, and Sennheiser G3 wireless lavs.

I'm getting pretty nice results using the softbox as the key light for the high-contrast, low-fill effect I like, but as we all know, getting a narrow DOF to isolate the subject is hard. Here's what I'm thinking of trying:
1) Set XF100 Gain at -6db
2) Manual Aperture at F1.8
3) Use Shutter Speed to control exposure
4) Have background as far away from subject as possible
5) Have camera as far away from subject as possible, and zoom in

For the last two I'm obviously limited by the space in which I'm shooting. If it matters, I'm shooting 1080p30 at 50Mbs.

Anything else I should be trying? Anyone have any samples they're particularly proud of for me to look at? Will I need screw-on ND filters?

Thanks In Advance,

[Les Wilson]

Keep in mind shallow depth of field is an illusion:
Depth of Field Myth

Never vary the shutter speed. If you are shooting 1080p30, your shutter is 30, period.

Is the -6db a typo? The most I've seen on Canon cameras is -3db. The XF100 has minus 6db of gain?

[Bob Leeds]

> Keep in mind shallow depth of field is an illusion:

Well, the article you linked to shows the effect I'm looking for is no illusion. Thanks for that, it confirmed what I suspected - keeping background further away and locating camera further away helps.


> If you are shooting 1080p30, your shutter is 30, period.

I do believe it's possible to choose a shorter (faster) shutter speed. See page 56 of the XF100 User's Manual.


> Is the -6db a typo?

Nope, see page 55 of the XF100 User's Manual.

[Mark Ahrens]

Originally Posted by Les Wilson

Never vary the shutter speed. If you are shooting 1080p30, your shutter is 30, period.

Why? Could you elaborate on that precept?
I've heard others claim if shooting 30p then 60 is max . . . don't get that either.

[Les Wilson]

Sorry. I was a little too tired and cryptic.

First, what you are trying to do is setup a shallow depth of field (sDOF) not Depth of Field (DOF) as the title of the thread indicates. Every camera setup has DOF but not every one has sDOF.

Secondly, sDOF is not natural. The eye and brain generally work it out so that everything is in focus. In using an sDOF, you are creating an artificial visual illusion of some things in focus and others not. That's all I meant by referring to it as an illusion.

1080p30 defines the rate at which the shutter opens is 30 times per second. The duration it stays open can be adjusted to affect exposure. But that's generally not recommended unless you desire the visual effects that go along with that e.g. a shutter speed of 1/250th will have a different look than 1/30th. For 1080p30, a shutter speed of 30 or 60 are the recommended ones and correspond to 360 degree and 180 degree shutter. If that's all you intended on doing then nevermind.

A better explanation and why these are the recommended speeds can be found here:
Shutter, shutter speed and shutter angle. | XDCAM-USER.COM

This is frequently discussed here. Here's a discussion that broke out about the XF:
http://www.dvinfo.net/forum/wedding-...shutter+degree

I recommend varying your aperture to adjust exposure. With the little 1/3" chip, it's unlikely you'll notice the difference in the depth of field between 1.8 and 3.2 but you will notice the difference in exposure. You can also add a dimmer to your lights to effect the exposure you want. Speaking of lights, there's many factors that go into a nicely lit interview including color temperature, existing light, reflection and background lighting.

Here's an informative article on lighting interviews:
Hellgate Pictures, Inc. - Lighting examples-3 point lighting -old school
Hope this helps.

[Mikko Topponen]

Completely disagreeing with Les here. Never use 1/30 with 30p unless you like that kindoff footage. Double the framerate is the regular value, it looks good on most situations.

You need the get the aperture as open as possible. And don't move the camera too far, keep it closer than the background.

[Les Wilson]

I don't disagree with you Mikko. I use 180 degree ergo 60p for 1080p30 and only go to 30 under duress.

[Olof Ekbergh]

It is easier to separate the talent from the BG when using a larger imager camera like a DSLR or an F3 AF100 or whatever.

However it can be done with 1/3" chip cams as well.

The first consideration is the back ground, if it is really busy, like an outdoor scene with lots of people cars etc moving in the background. Then shoot more on the telephoto end of the lens moving the camera away from the subject as well. In this situation you usually have more space to do that. People in the BG that are in focus doing something can be very distracting unless it is relevant to the scene.

When shooting indoors, pick your back ground so that it is not too busy, and use a larger aperture like f1.8. You can still get a bit of blur in the back at a normal to short tele setting. Also remember you can really use light to separate the BG. If you can't blur the BG much then pick a section of wall that has no or only a few items on it and light it to create a soft gradient, then light your talent so the light is the opposite of the BG. If your BG is lighter on the left then have your key light on the right, this is pretty simple to do and works very well. Another note, it is always a good idea to explain your light so it looks right not to theatrical, like the gradient on the wall can come from a window, doorway or a lamp in the shot.

I would also never change the shutter speed to control exposure, I use 180 degree shutter or 1/60 shutter for 30p. This will be very pleasant to view as this is what we are used to seeing. Faster or slower shutter are special effects and can be used for creative reasons, but 180 degree is normal.