Basics of documentary interview HD video shooting

parallactic-pictures

parallactic-pictures

Active member
Hi guys,

Boy, since purchasing my Canon 7D in December, my life has changed. For the better. I now spend most weekends out with my girlfriend, taking photos of as many parts of Los Angeles as we can. Before the 7D, I had a Canon Powershot SD1100 IS. This is your basic consumer Best Buy camera. I got it for Christmas two years ago for about $150. So before the 7D I was primarily a guy who would whip out a camera at parties or events and snap a few terrible photos that I'd then share on Facebook.

Point is, I didn't know much about the basics of Photography 101. But since the 7D, I've had to learn these basics. And I've embraced them fully and love the challenges and opportunities they present. As a result, my photography has improved greatly.

Now, the other funny thing about the 7D is that, as far as being a filmmaker, I was primarily a writer/director. I'd always want to look through the viewfinder before "action" was called, so I could make sure the shot was composed to my liking, but I didn't know much about cinematography. But I knew the day would come where I'd start wanting and needing to learn more about it. And as it turns out, that day was when I got my 7D. :)

I'm now doing a lot more video shooting as a director. And friends and people I know, have come out of the woodwork to have me help them on projects, shoot weddings, and most recently, help out on a project where I'll be a B-Camera Man on a documentary style shoot.

We'll be shooting interviews with subjects. I'm not sure if the subjects will be sitting, or walking around. But I know that my purpose is to be the back-up camera man and capture an alternate angle with my 7D. The primary cameraman is using the Sony EX1. And the filmmakers have stipulated to me, that the Sony camera will serve as the primary footage. Still, I want to do a good job, so I've been researching documentary interview style shooting lately, and this has led me to some questions.

In Phillip Bloom's latest blog about filming interviews with dSLR's, (found here: http://philipbloom.co.uk/2010/01/23/is/), he says this:

"You really wouldn’t want to shoot an interview below F2.8 anyway unless the interviewee is like a statue otherwise you will struggle to keep focus. Even F2.8 is tough. Around F4 is nice and safe. But if the interviewee is pretty still I tend to push for F2.8 as it looks so nice."

Now, when he says "below F2.8," does he mean apertures like F2.4, F1.8 etc? Or does he mean everything literally above F2.8, like 3.5, 4, 5.6, etc?

And is he then also saying that, as your lenses get faster (F2.8, F1.8, etc), it's easier to lose focus if a subject moves? I guess that makes sense because more light is being let in as that aperture opens and hence, you have the potential for more motion blur, same as you would with a slower shutter speed.

But then, I also know that more light gives a better exposure and would make a subject easier to get focus on. That's why people prefer faster lenses for low light shooting.

So really, these are my initial questions. And please don't giggle, I'm really new to all this, so while these questions may seem basic, I just need some clarity on them:

1. When someone says "stop it down"... do they mean reduce the aperture, and hence, go from F2.8 to F3.5 to F4 to F5.6 etc? And if someone says "Above 2.8", do they mean a wider aperture, and hence, 2.4, 1.8. 1.4 etc?

2. If a lens is faster and hence, something like an F2.8, will motion blur become more apparent? I would think a faster lens would be more sharp, and have an easier time getting focus then something that was F4 or "below".

I have more questions about documentary interview filming, and other tips I'll need, but I'll start with these basic questions. Thanks, all.
 
1. yes stopping down reduces the aperture to a smaller size corresponding to increasing depth of field and f stop numbered as f1.2, f1.4, f1.8, f2, f2.8, f3.5, f4, etc...
f2.8 is quite shallow so f4 seems indeed better to avoid losing too much focus on someone's facial features if moving a bit while talking.

2. motion blur depends on your shutter speed rather than lens. slower shutter will appear more blurry by blending more movement on the frame. use a fast shutter and it'll be strobing. 1/50 or 1/60 is recommended depending on your country's AC frequency to avoid light pulsing.
sharpness is often best at about 2 clicks down from wide opened aperture. an f2.8 lens will be sharper at f4 than an f4 lens fully opened. both will be good at f8.

hope that helps
 
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I have been using my 7d as a tighter, 15-25 degree off-axis interview camera that "drifts" slightly.

The HPX-500 is my safety lock down MS to MCU shot.

They cut back and forth wonderfully.
 
rhervag said:
1. yes stopping down reduces the aperture to a smaller size corresponding to increasing depth of field and f stop numbered as f1.2, f1.4, f1.8, f2, f2.8, f3.5, f4, etc...
f2.8 is quite shallow so f4 seems indeed better to avoid losing too much focus on someone's facial features if moving a bit while talking.

2. motion blur depends on your shutter speed rather than lens. slower shutter will appear more blurry by blending more movement on the frame. use a fast shutter and it'll be strobing. 1/50 or 1/60 is recommended depending on your country's AC frequency to avoid light pulsing.
sharpness is often best at about 2 clicks down from wide opened aperture. an f2.8 lens will be sharper at f4 than an f4 lens fully opened. both will be good at f8.

hope that helps
Click to expand...

Okay, let me see if I get this:

  • Stopping down is decreasing the aperture size, and thus, making the image darker.
  • Stopping up is increasing the aperture size... making it wider, and letting more light in, hence, brightening the image.
  • If I say something like, "It's above an F4..." then I'm saying it's a 5.6, or anything higher in number than F4.
  • If I say a "high f-stop", I mean a faster lens. So a 1.4 fs would be one of the "highest". You would never talk about a 22f/s as being "high". Even though that's a larger number, it's considered a lower fstop. So really, the language is reversed here.
  • The higher the fstop, the more shallow the depth of field. So at 2.8fs, I'll get more shallow depth of field than at f4 or f5.6.
  • But the more shallow our depth of field, the harder it is to get focus, especially on a moving subject. So unless my interviewee is sitting perfectly still, a 2.8fs may be risky, and I'd be safer with an f4.
Lastly, can you explain exactly what you mean when you say this:

"sharpness is often best at about 2 clicks down from wide opened aperture. an f2.8 lens will be sharper at f4 than an f4 lens fully opened. both will be good at f8."

When you say two clicks down... do you mean two stops down? I know that sometimes, I'll have a picture set, but I'll look through the Viewfinder and not like the exposure I'm getting. So I'll go manual on my fstop, and spin the wheel down two spots, hence, darkening the shot slightly.

So then, two clicks down from an f2.8 would be an f4. But that will be better than a f4 lens wide open, because the f2.8 is just a better built lens? That last part sort of makes sense to me. I'm just a little off with the physics still.
 
Aperture is a beast until you "get it" -- then once it clicks...you realize even more how confusing it is.

The number, the "f stop" -- is the result of a math problem, where diameter is on the bottom of the fraction. So as your diameter gets bigger (Larger hole. More light.) the number gets smaller.

So now that we understand why f-stop numbers are exactly reverse of what we expect, let's see if we can't get a good understanding of the notation.

parallactic-pictures said:
Okay, let me see if I get this:

  • Stopping down is decreasing the aperture size, and thus, making the image darker.
  • Stopping up is increasing the aperture size... making it wider, and letting more light in, hence, brightening the image.
Click to expand...


  • That's right -- but keep a close eye on the numbers as that happens.

    Stopping down is decreasing the aperture size, making the image darker, which means using a higher number. Like stopping down to 4.0 instead of using 2.8.


    Stopping up (Or, more commonly, opening up) is the opposite. Going from a higher number to a lower number, which makes your diameter bigger, which lets more light into the camera. It also narrows the window of what's in focus.

    [*]If I say something like, "It's above an F4..." then I'm saying it's a 5.6, or anything higher in number than F4.
    Click to expand...

    Yes.

    [*]If I say a "high f-stop", I mean a faster lens. So a 1.4 fs would be one of the "highest". You would never talk about a 22f/s as being "high". Even though that's a larger number, it's considered a lower fstop. So really, the language is reversed here.
    Click to expand...

    You're all turned around...which is understandable. Higher f-stop means a higher number. Higher number is a "slower" lens. f22 is high, in fact, around the highest f-stop for most cameras.

    [*]The higher the fstop, the more shallow the depth of field. So at 2.8fs, I'll get more shallow depth of field than at f4 or f5.6.
    Click to expand...

    You have the numbers right -- 2.8 is going to give you less window-of-sharpness than f4 or f5.6, but that's a lower f-stop, not higher.

    [*]But the more shallow our depth of field, the harder it is to get focus, especially on a moving subject. So unless my interviewee is sitting perfectly still, a 2.8fs may be risky, and I'd be safer with an f4.
    Click to expand...

    Yeah. Because your window-of-sharpness is narrower.

Lastly, can you explain exactly what you mean when you say this:

"sharpness is often best at about 2 clicks down from wide opened aperture. an f2.8 lens will be sharper at f4 than an f4 lens fully opened. both will be good at f8."
Click to expand...

I'm not sure what was meant by that. If you're using a lens that lets you control the aperture on the lens (As opposed to on the camera body...do you 7Ders ever do this?), then it usually turns in little "clicks" -- but the clicks are not necessarily a full stop.

So then, two clicks down from an f2.8 would be an f4. But that will be better than a f4 lens wide open, because the f2.8 is just a better built lens? That last part sort of makes sense to me. I'm just a little off with the physics still.
Click to expand...
[/quote]

Yeah -- that's the idea. It's not the the lens is "better built" -- it's just that most lenses are at their sharpest a stop or two down from "wide open." So just as you described, most 2.8s start to look their best at 4.0, and most 4.0s start to look sharp around 5.6, and so forth.

It really depends on the lens though. I have a 50mm/1.7 that looks pretty good at 2.0, and a Sigma (of all things!) 24mm 2.8 that looks great right there at 2.8. Also -- on the GH1 anyway, and I imagine it'd be similar on the 7D, in video mode the camera is way "under-resolving" the lens anyway...meaning that the difference in the quality of sharpness (of a wide open lens, vs. one that's slightly stopped down) is significantly more pronounced in photo mode than video mode.

But really that's where I better bow out of this conversation, because I'm using a cropped camera (Meaning that I'm only using the center of the lens...which is the sharpest area, even "wide open"), and you're not.
 
Just remember when you "stop down" (or decrease the aperature size, increasing the "f-stop number", say from 2.8 to 4, you need to make a corresponding change to the shutter speed (decrease or slow it) to allow more light in, or the image will be too dark.

Also, "strobing" is really just a lack of motion blur, in other words, the image is unnaturally sharp, and a slower movie speed ie 1/24th of a sec, will show in a big way the difference between two frames if they're too sharp, thus creating the "strobing".
 
aperture affects depth-of-field.
the smaller the aperture, the more 'stopped-down' it is, the deeper your depth-of-field......the greater the range of depth of things that are in-focus.
the larger the aperture (lower f-stop), the more shallow your depth-of-field.
if your dof is very shallow, the subject might lean forward an inch and suddenly be out-of-focus.

btw, Saaby, the 7D crops too, just not as much as the gh1. the 7d isn't 35mm, it's aps-c.
 
"You really wouldn’t want to shoot an interview below F2.8 anyway unless the interviewee is like a statue otherwise you will struggle to keep focus. Even F2.8 is tough. Around F4 is nice and safe. But if the interviewee is pretty still I tend to push for F2.8 as it looks so nice."
Click to expand...

It's kinda of hard to make a generic statement about what aperture to shoot an interview at IMHO. If you're shooting at 50mm f/2.8, you're going to have a lot deeper DOF than at 100mm f/2.8. Focal length has every importance as the aperture when it comes to DOF.
 
In defense of Philip Bloom, here is the full paragraph he typed on his blog, which I pulled that quote from:

"I tend to shoot these interviews on a zoom lens, this gives me the freedom the change the size of the shot without stopping and starting as I would have to do with a prime lens. The F2.8 70-200 mm Canon IS is my lens of choice for this. You really wouldn’t want to shoot an interview below F2.8 anyway unless the interviewee is like a statue otherwise you will struggle to keep focus. Even F2.8 is tough. Around F4 is nice and safe. But if the interviewee is pretty still I tend to push for F2.8 as it looks so nice."

So he does mention the lens he would be using, and hence, the focal lengths.
 
He does mention the lens, but didn't really reference the focal lengths when determining the f/stop and how much DOF you want in an interview.

Regardless, just remember to think about the focal length!
 
patssle said:
He does mention the lens, but didn't really reference the focal lengths when determining the f/stop and how much DOF you want in an interview.

Regardless, just remember to think about the focal length!
Click to expand...

Well, I just bought a Sigma 18-50mm lens for this. It doesn't have vibration control though. But it's a constant 2.8fs aperture across the entire focal length. I'm not sure how they're going to want me to frame this up. But maybe suggest me some good fstops for this focal range, if you don't mind.
 
For the moment put the camera on auto iso

find something like a fence

point your camera along it and focus on a fence post say 2meters away

selcet your longest lens or zoom in to the max to see the effect most powerfully

look at the picture

stop down - close - make the number closer 2 F22 - the aperture and see the

depth of field increase - more goes in focus (more fence posts are sharp)

focusing at a wde aperture - 1.4,2, 2.8 is hard - focus becomes less critical after that

but those same apertures look cool - lots of cinematic blur - and work well in low light becase they let in a lot of light enabling you to keep your ISO low

low ISO is good because there is less noise in the footage
----
Aperture means hole - small number = big hole ; F1.4 is a small number F22 is not

Big hole = lots of light in and more blur (why more blur ? rip two holes big one little one in a cereal packet and shine a torch through them - bigger hole more blur)

---

Oh yea and with a wider lens you get 'more depth of field - more in focus for a given aperture

(debatable by nerds but a good rule for now)

20 is a wide lens - 200 is a long lens, PB is using a 70-200 which is zoom offering a selection of different reasonably long lenses

the 70-200 will have a lot out of focus if you are reasonably close to the subject because it is long

20 is not a wide lens on the EX1 becase it has a smaller chip and only sees a tiny bit of image the lens is projecting)

=====

now turn that ISO back off auto !

and learn to get a nice exposure and attractive depth of field by choosing your lens lenght, Fstop and ISO in a finely tuned harmony to create the cinematic look of your dreams all while keeping the shutter on 1/60th if you are in the us or 1/50th in the EU

And maybe do some films in the park before the project - if its sunny you will be back to ask what a ND filter is (it cuts the light enabling use of a wide aperture to create cinematic blur on a sunny day without messing with your shutter speed - messing with your shutter speed can make stuff look like saving private ryan)

S
 
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Thanks all! Turns out I guess I knew all of this. The only thing it seems I got backwards was some of the wordage. Btw, the shoot I worked on went great. This camera really is a wonder.
 
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