Managing depth of field for a low end camera

[Todd Terry]

This has been discussed several times in this and other forums, such as the HDV forum. I’d suggest doing a search using the terms “depth of field” or “DoF.”

Unfortunately you are asking more of your camera that it was designed for. The tiny 1/3″ chips in a small DV camera just make it fairly impossible to get very shallow depths of field… it just prinicpals of physics and optics.

The DoF will get shallower the more you zoom in, so you may be able to get the effect you want with longer/tighter shots.

Barring that, you would need to use a depth-of-field lens converter. That would do exactly what you want… but be forwarned: you say you have a very “low end” DV camera… that being the case a good DoF converter can cost several several times as much as the camera itself. I’m not sure I would make that kind of investment unless you could get your hands on a higher-end camera.

Good luck!

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com

[Jeffrey Buras]

Without buying new equipment, your only option is to get far away and zoom in as much as possible.

Larger sensors and lenses with very wide apertures give professional cameras their shallow depth of field. Longer focal lengths (aka zooming in) also gives a shallow depth of field.

Depth of field converters are also used. Like Todd said, they are more expensive than it’s worth for your camera. If you spent the money for a DoF converter, you might as buy a new camera.

[Boyd Mccollum]

point of clarification – there are only 2 elements that affect depth of field (DoF), that is f-stop (aperture) and image size (or in the case of video, sensor size). The smaller the image/sensor size, the greater the DoF and the lower the f-stop (for example f/2.0), the shallower the DoF. Depth of Field is the result of a mathematical relationship between these two, and the focal length doesn’t matter.

Zooming in, or increasing your focal length, creates the illusion of a shallower DoF, but this is due to higher magnification. Longer focal lengths flatten perspective, which makes the background larger relative to the foreground (basically magnifying the inherent blur in the background image). Focal length can also affect the distribution of the DoF around the focal plane: at a shorter focal length (wide angle), the majority of what is in the DoF takes place behind the focal plane, while at a longer focal length (telephoto), the DoF is more evenly distributed in front and behind the focal plane.

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[Steve Wargo]

[boydmcc] ” Also remember, a shallow DoF is not the sole objective of good cinematography. “

Thanks for that. In the past year or so, it seems like all I hear about is the need to have the background out of focus at all times. The people who are concerned own the small cameras with the small chips. The one major problem is that the Image records upside down. I have seen cameras and monitors upside down and DPs and crew members concentrating all of their efforts on dealing with this instead of doing their real job. They will have crummy lighting and a non-existent sound package, but all they care about is that soft background.

Poor priorities for sure.

Steve Wargo
Tempe, Arizona
It’s a dry heat!

Sony HDCAM F-900 & HDW-2000/1 deck
5 Final Cut (not quite PRO) systems
Sony HVR-M25 HDV deck
Sony EX-1 on the way.

[Steve Wargo]

In my original post, I started to move a remark and deleted it altogether.

Thanks for that. In the past year or so, it seems like all I hear about is the need to have the background out of focus at all times. The people who are concerned own the small cameras with the small chips. The solution, it seems, is the adapters that mount film lenses onto the front of the small cameras The one major problem is that the Image records upside down. I have seen cameras and monitors upside down and DPs and crew members concentrating all of their efforts on dealing with this instead of doing their real job. They will have crummy lighting and a non-existent sound package, but all they care about is that soft background. This is not to say that the adapters shouldn’t be used, but they need not be the primary place to put money when the budget is really tight. I will be more impressed by an awesome sound track than I will with a fuzzy background.

I have had distributors ask “How is the soundtrack” but I’ve never heard one say “So, the background’s out of focus, right?”

As I said before, poor priorities.

Steve Wargo
Tempe, Arizona
It’s a dry heat!

Sony HDCAM F-900 & HDW-2000/1 deck
5 Final Cut (not quite PRO) systems
Sony HVR-M25 HDV deck
Sony EX-1 on the way.

[Todd Terry]

All true and valid points… but…

[Steve Wargo] “The one major problem is that the Image records upside down. I have seen cameras and monitors upside down”

Well… NOT if you use a good one 🙂

We use a PL mount DoF converter almost every day with our little Canon XLH1 (not with an upside-down image)… but not purely so I can get a super soft background. Rather I use is so I have a controllable background… as a cinematographer sometimes I want DoF super shallow, sometimes deep, sometimes in between. On a “real” movie set how deep the DoF is, is one of the first thing that the DP considers… and then the lighting is affected accordingly to allow him to get that. Plus it allows me to use real cinema lenses, lenses that are many MANY times better than any video lens that I could ever hope to use on the camera.

It’s just part of the package for us… no more (or less) important than good sound, lighting, or anything else.

Without some kind of conversion to a 35mm frame size… video will never truly look like 35mm film (which is obviously the goal of many people). Even the highest-end HD at 24p… it still looks like video. GREAT video, but video nonetheless. I remember watching “Once Upon a Time in Mexico” in the theatre (before I knew how it was shot) and remember thinking, “Why is this VIDEO”? For me, a good DoF converter just gives the image the “look” that puts it over the top. Not necessarily because of shallow focus, but because of a number of factors combined.

I thinkk a lot of it has to do with one’s background, and what one is used to shooting. For the videographers who are used to electronic images, then HD knocks their socks off, and rightly so. But most cinematographers who have been used to shooting film feel that HD just doesn’t look “quite right” to them, even at 24p. It’s the up-and-coming kids who think a DoF converter suddenly turns their little palmcorder into a Panavision that have unrealistic expectations and put too much weight on using them.

They are just a tool, they aren’t “God’s gift to filmmaking”… but to be honest, if I didn’t have my P+S Technik Mini35 and great lenses I would be shooting 35mm film a little later today, not HD.

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com

[Steve Wargo]

Todd. You are not the guy that I was talking about. But I think you knew that. Your input is always level headed and shows your years of experience.

Steve Wargo
Tempe, Arizona
It’s a dry heat!

Sony HDCAM F-900 & HDW-2000/1 deck
5 Final Cut (not quite PRO) systems
Sony HVR-M25 HDV deck
Sony EX-1 on the way.

[Bob Cole]

[Jeffrey B.] “Without buying new equipment, your only option is to get far away and zoom in as much as possible.”

Somebody correct me if I’m wrong, but I think this is a common misconception. If you go far away and zoom in to, say, a head-and-shoulders shot, you’ll have as much DOF as if you stayed close and zoomed out for the same head-and-shoulders frame.

The solution is to move the subject as far from the background as possible. For interiors, place the camera close to one wall, and bring the subject as close to the camera as you can.

Also, of course, shoot wide open, using a higher shutter speed if necessary. This can be tricky if you use the zoom a lot, as tele settings generally have a higher “wide open” f-stop.

You can also create the impression of shallow DOF by your choice of background (large objects without detail) and the lighting on the background (defocussed pattern lighting).

But the human eye has infinite DOF, so perhaps this is a new esthetic. Well, not so new, Citizen Kane.

Bob C

MacPro 2 x 3GHz dualcore; 10 GB 667MHz
Kona LHe
Sony HDV Z1
Sony HDV M25U
HD-Connect MI
Betacam UVW1800
DVCPro AJ-D650

[Todd Terry]

[Bob Cole] “Somebody correct me if I’m wrong, but I think this is a common misconception. If you go far away and zoom in to, say, a head-and-shoulders shot, you’ll have as much DOF as if you stayed close and zoomed out for the same head-and-shoulders frame.”

Sadly, no. DoF is a function of a number of things including f-stop, size of image (film frame or chip size) and lens focal length. In the 35mm world, just as an 80mm prime lens has a much shallower depth of field compared to, say, a 28mm lens… by zooming in you are increasing the focal length of the lens and correspondingly decreasing the depth of field.

The other suggestions (shooting wide open, etc.), are legitimate, but unfortunately in practicality don’t have too much effect. The little 1/3″ sensors are so tiny in small camcorders that even a wide-open iris will have DoF almost as deep as one that is significantly stopped down.

If one desires a truely shallow depth of field with a small camcorder, the only real solution (barring shooting everything with as looooong a lens as possible… i.e., zoomed in) is to use a lens converter.

[Bob Cole] “Well, not so new, Citizen Kane.”

Yep, extremely shallow DoFs are a bit of a modernism. DoFs in Welles’ day were indeed often very deep (Kane’s cinematographer Gregg Toland especially was an advocate and deveoper of “deep focus”). These were aesthetic decisions accomplished by wide angles, stopped down lenses, and even special multi-focal (“cut in half”) lenses and attachments that would focus part of the frame for foreground and part of it for background. Also, this was before “superspeed” days and maximum f-stops on lenses of the day weren’t as large as presently available.

Times, they are a-changin’…

T2

__________________________________
Todd Terry
Creative Director
Fantastic Plastic Entertainment, Inc.
fantasticplastic.com

[Bob Cole]

[Todd at Fantastic Plastic] “[Bob Cole] “Somebody correct me if I’m wrong, but I think this is a common misconception. If you go far away and zoom in to, say, a head-and-shoulders shot, you’ll have as much DOF as if you stayed close and zoomed out for the same head-and-shoulders frame.”

Sadly, no. DoF is a function of a number of things including f-stop, size of image (film frame or chip size) and lens focal length. In the 35mm world, just as an 80mm prime lens has a much shallower depth of field compared to, say, a 28mm lens… by zooming in you are increasing the focal length of the lens and correspondingly decreasing the depth of field.”

Of course, but that’s not what we were discussing. The suggestion was to decrease the DOF by moving the camera further away and zooming in. Assuming a constant imager size, and a constant subject size (e.g. a head-and-shoulders in both cases) and subject position relative to the background, that doesn’t work. You’ll get a narrower slice of the background, but it will be virtually as sharp. I can’t find the source where I first saw this, but take a look at
https://www.cambridgeincolour.com/tutorials/depth-of-field.htm or https://www.agilelevin.com/outoffocusessay.htm

I agree with your observation about how difficult it is to make a 1/3″ imager have shallow DOF. It’s made me much more careful about choosing a background and positioning the subject (I’m talking interviews here).

What I’m wondering about right now (as a Sony Z1 owner), is whether there is enough of a DOF difference to make a difference, between the 1/3″ imager and a 1/2″ (as in the new Sony EX). I have come to appreciate the light weight of the Z1, and I especially like the ergonomics of the EX. Do you think there will ever be a 2/3″ camera in something like the EX form factor? I dislike the weight of the new “cheap” Panasonic 2/3″ shoulder-mount cameras — & I really like being able to carry around an HD-flavor video camera like I used to carry an SLR!

Bob C

MacPro 2 x 3GHz dualcore; 10 GB 667MHz
Kona LHe
Sony HDV Z1
Sony HDV M25U
HD-Connect MI
Betacam UVW1800
DVCPro AJ-D650