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-   -   improving focus range during interviews (XL2) (https://www.dvinfo.net/forum/canon-xl-gl-series-dv-camcorders/74055-improving-focus-range-during-interviews-xl2.html)

Charles Penn August 22nd, 2006 08:00 AM

improving focus range during interviews (XL2)
I could use some input with respect to finding sharp focus during sit-down interviews I'm conducting. Much to my chagrin, I've found a few shots where my talent leaned forward or backward and my focus is soft. I'll have to cover it with b-roll but I need to learn NOT to duplicate this again.

Part of my problem is directly related to trying to be a one-man gang! It's difficult to concentrate on the interview, follow-up questions, change the shots, pan and tilt with talent, etc. The soft focus came during interviews I did without a monitor. The softness of the shot did not come through the looking at it in the viewfinder.

However, there must be a setting I could use that would afford me the best chance of circumventing soft focus. There's only a few shots I'm using: Wide shot of talent at desk with bookshelf in background, chest up to face with a little head room and a CU cutting off the top of head. Of course, I'm zooming in on my talent's eyes to set focus and pulling back.

As for lighting, I'm using a Rifa 44 softlight as key and a tota --usually bounced off wall to fill/ kick. Lighting doesn't appear to be an issue. Or will more light improve my focus range?

As most have suggested, I've been running in manual and tweaking my iris to adjust the exposure (not sure what the actual iris setting is as I'm at work currently.

Surely, there's something I can do to improve my focus range. Again, everything is a one-on-one sit-down interview. Thanks

Greg Boston August 22nd, 2006 08:11 AM


Originally Posted by Charles Penn
Surely, there's something I can do to improve my focus range. Again, everything is a one-on-one sit-down interview. Thanks

You'll mainly need to shut the aperture a bit more to gain more depth of field so the talent stays in focus. Use a good monitor and set critical focus to the talent's normal position. Have them move forward and check for softness. If they go soft, close the iris a bit. You might have to add light to compensate for stopping down.

Funny, most folks complain about too much DOF with mini-dv. You have to really work to get shallow DOF.


Josh Bass August 22nd, 2006 08:27 AM

Also, how far back is your camera from talent?

I usually try to get as far back as possible, for shallow depth of field (8+ feet seems to be a good distance), but you might want to try the opposite.

You don't wanna be so close that you don't have to zoom in at all (or else when they lean in, they will appear to grow larger 'cause you're at the wide end of the lens, and will have the optical distortions that come with that--but then again, maybe you do). Or maybe you do--I've seen interviews shot this way, and they have a different character to them. Kinda cool for the right situation.

Anyway, Maybe try moving the camera close enough so that you still have to zoom in to get the desired framings, but not very much (maybe just enough to "flatten out" the depth in the shot, i.e. getting rid of the "wide angle" look.) The more you zoom in, the less depth of field you have.

This will of course make it so your background is in focus (mostly likely, unless you're able to shoot in giant rooms), but maybe that's okay for you.

Charles Penn August 22nd, 2006 09:35 AM

Josh, I would guess that my camera is 8-10 feet away from the talent. I'll try moving it closer.

Greg, thanks for the suggestion @ checking focus by having talent lean in and back. Of course, most of the problem (besides the variables of iris setting and distance) was due to me not having a monitor! The viewfinder image is not dependable. I found that out the hard way.

Greg, you mentioned that "You have to really work to get shallow DOF." Please explain that to me and don't worry about appearing to talk down to me. I need to understand what you mean. Also, is there any way to fix soft focus in post? Thanks.


Josh Bass August 22nd, 2006 10:08 AM

I think I can answer. . .

with the XL2, a 1/3" chip camera, you have more depth of field and any given focal length (how far you're zoomed in), given a certain aperture and focus distance, than you would with a 2/3" or 1/2" chip camera. Therefore, you have to jump through many more hoops (opening up iris all the way, putting the camera far back from the subject and zooming in, putting the subject and background a great distance from each other) to get shallow depth of field with the XL2 (or any other 1/3" chip camera) than you would with one with a larger chip. That's not to say that if you had a digital betacam camera you'd have super shallow depth of field, just shallow-ER than a miniDV camera. In other words, at a given focal length (amount you're zoomed in, expressed in millimeters, say 70mm, for example), and a given focus distance (e.g. 15ft), and given aperture (say, f2.8), you will have more depth of field with the XL2 than you would with a camera with a larger chip, like an F900 or something, if you were to compare the two by shooting the same subject, side by side.

Greg Boston August 22nd, 2006 02:10 PM

Josh expressed it very well. What we are referring to is optical properties and the laws of physics WRT bending light rays and collimating them at a given point (critical focus).

If you wanted to blur the background better while allowing your talent to lean forward, you could actually set your critical focus with the talent leaning forward. Then when they lean back, they won't be at critical focus, but the background will get thrown out behind them even quicker this way.

Here's another analogy. Imagine your depth of field while picturing a football field from beyond the end zone. Also, imagine that the goal lines represent the front and rear limits of acceptable focus.

Most of the time you would have critical focus set on the subject which places them at the 50 yard line. But what if you set critical focus at the 20 yard line closest to you? Your subject is still at the 50, and the furthest acceptable focal point is no longer the far end zone, it has move toward the subject and the end zone will be out of focus.

Hope I haven't confused you further.


Josh Bass August 22nd, 2006 03:37 PM

What's that generic rule about the thirds and depth of field? And what situations does it apply in?

Where D = point of critical focus (usually the subject)

You have 1/3D (one third of D) in front of the subject in focus, and 2/3D behind the subject in focus.

Maybe that's way off. But at least in my way off desription should allow some to chime in and say it correctly.

Greg Boston August 22nd, 2006 04:13 PM

Yeah Josh, it's really not a '50 yard line' scenario, but close. I was simplifying a bit for the sake of illustrating the concept.

Here's an excerpt of the article about DOF by Jeff Donald on DVINFO's articles page.


the formula for DoF as it appears in the "American Cinematographers Manual," 8th edition, pages 698-699.

Hyperfocal Distance: h = f2 / ac

f = focal length of lens
a = aperture diameter (f/stop number)
c = circle of confusion

Depth of Field, Near limit: hs / h + (s - f)

Depth of Field, Far limit: hs / h - (s - f)

h = hyperfocal distance
s = distance from camera to object
f = focal length of lens

Charles Penn August 23rd, 2006 04:50 AM

What about my question about post? Is it possible to 'fix' soft focus in post?

Richard Hunter August 23rd, 2006 06:28 AM


Originally Posted by Charles Penn
What about my question about post? Is it possible to 'fix' soft focus in post?

Hi Charles. If the focus is only slightly off you can use a little bit of sharpening and see if that helps. If it is very soft I doubt if it can be saved.


David Lach August 23rd, 2006 10:38 PM


Originally Posted by Richard Hunter
If it is very soft I doubt if it can be saved.

Really? But what about all those CSI episodes where they miraculously turn the lowest res, softest focused footage into sharp HD images in a matter of seconds?

Yes, I'm kidding.

Best way to get good focus is to control and tweak it at the source with a sharp finder. That's why I bought the FU-1000 for my XL2. Never held the stock VF in high regards, I'd always get the impression I was working blind so to speak. Try it and you'll never go back. Alternatively a good, relatively high res field monitor can do as well.

I think F5.6 is the sweet spot for getting sharp images and relatively deep DOF. Won't help much if you're too far away though. As mentioned try to stay pretty wide. But all those compromises aren't necessary when you have a sharp ideally CRT viewfinder or monitor to re-adjust focus depending on talent position.

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