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Question about exposure settings

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Duke Sweden
Question about exposure settings
on Aug 11, 2016 at 10:30:13 pm

I'm just an amateur and I don't have a fancy lighting studio or outdoor equipment but the answer to my question might help others.

OK, when shooting a scene that will end up dark and moody, should one try to get exposure as close as possible to that look in camera, in other words crush where they're going to be very dark in the final color grade, or should you try to get as bright an image as possible short of overexposure, and darken in post?

It seems to me that when I darken in post I get a lot of noise, even in the brighter areas. I'm using a Panasonic G7, btw, and I'm not entering anything at Cannes this year, if you catch my drift ;-)


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Richard Herd
Re: Question about exposure settings
on Aug 15, 2016 at 8:57:16 pm

We are gonna talk about contrast ratio. That's the name for the idea that every image has the darkets pixel and the brightest pixel. We measure the contrast ratio in f/stops. Our eyes for example can see 12 or so at one time. Video cameras like the one you're using can only see 5, and it doesn't matter which five they are, just five.

You'll also notice that your camera will have a minimum amount of lux. That is, how much light it needs in order to render an image. Usually this is pretty dark, but not as dark as the human eye can see.

What does this all mean?

Let's suppose, like me, you like to expose an image at 2.8. THis means your camera will actually record four other f/stops (from darkest to lightests): 1.4, 2.0, 2.8, 4.0, 5.6 .

The reason I do this is because we are converting light into data. The 1.4 ensures that I have recorded "darkness" as data and later, I can adjust the black point in post because it is data. Had I shot lower than that, the darkness is still dark of course, but it is no longer data, so you can assume that anything darker than the 1.4 is gone. Same thing on the other end. the 5.6 ensures that the white points are actually white and not clipped -- but everything beyond that is gone, clipped. It cannot be recovered.

So now back to your question: You want to shoot a properly exposed image.


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Duke Sweden
Re: Question about exposure settings
on Aug 15, 2016 at 10:03:28 pm

Wrong. I want to know IF I should shoot a scene that is supposed to be dark, like, say, the big bad wolf in the Black Forest, should I expose the shot as close to what I want it to look in camera, or get as much information/data as possible with brighter lights and THEN darken in post. Believe it or not, you've given me the answer with your example regarding the four f/stops. Thanks!

For the record, the kit lens only goes to 3.5 but it will do for now.
Cheers!


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Alan Lloyd
Re: Question about exposure settings
on Aug 15, 2016 at 11:41:11 pm

The answer really is to keep things in the middle.

Shoot your big bad wolf at a more or less normal exposure and you'll have more latitude to do what you want to the image in edit. Take it to extremes of luminance or darkness (or saturation, for that matter) and you constrain your options rather dramatically.

Too much flat black or white (too dark, too blown out) and you have nothing to work with.

I once had someone send me footage where a speaker's face was pure 100 IRE white. All I could do was make it gray, not recover information on features or skin tone. Same thing if you go too dark. Once you've hit 0 (or 7.5) there's nothing usable left.


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Richard Herd
Re: Question about exposure settings
on Aug 15, 2016 at 11:48:00 pm

For me, I like to work in whole f/stops, so I would shoot it on a 4.0, so we're looking at: 2.0, 2.8, 4.0, 5.6, 8.0. When you get into post this will roughly line up to the IRE (20, 40, 60, 80, 100).

The art of the cinematographer is to shape the light into a proper exposure. We used to call it a "dense negative." We get the key light, the fill light, and the negative fill. Poor negative fill. He never gets much attention, but worth looking up ;)


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Duke Sweden
Re: Question about exposure settings
on Aug 16, 2016 at 1:17:42 am

You guys have no idea how helpful you've been. Thanks! btw, Richard, I misread your last sentence in your previous comment. I thought you were restating what you thought was my question, so I said "wrong". I realize now you were answering my question so I hope you didn't think I was being a jerk.

The people in Premiere Pro forum know me and what I do. Here's a sample of the type of stuff I do so you understand where I'm coming from when I say I'm an amateur. You don't have to watch the whole thing, obviously. The first few seconds should suffice ;-)







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Richard Herd
Re: Question about exposure settings
on Aug 16, 2016 at 9:41:38 pm

Haha. Pretty silly.

If you're gonna pull keys, definitely do not underlight or overlight -- do it just riiiiight.


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Duke Sweden
Re: Question about exposure settings
on Aug 16, 2016 at 10:46:06 pm

Thanks, I aim for silly ;-)

My question of course has nothing to do with my green screen stuff. I'm trying to do some real life stuff soon and I wanted some advice, which all of you have given me in abundance. Thanks again!


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Todd Terry
Re: Question about exposure settings
on Aug 16, 2016 at 1:45:57 am

[Richard Herd] "For me, I like to work in whole f/stops..."

Very curious, Richard... why do you prefer this?

For me personally, one of the beauties of using cine lenses is the fact that the aperture rings have no "clicks" so fractional f-stops are easy. I probably rarely if ever shoot at exact whole f-stops, or probably not even halves or thirds, either, since those in-between settings are just as easy as whole ones.

Definitely not saying my way is right and yours is wrong by any stretch, just wondering what your theory behind that is... I'm always up for learning something new (especially if it makes things better or life easier).

Just incidentally... for the past few years I've tried (notice I said tried) to do what many of my top hero DPs do, and that's not choose/adjust f-stops for exposure at all (well, except incidentally), but rather to choose f-stops for the desired depth of field, and then light (and filter and sometimes even adjust ISOs) accordingly to expose properly. This is a little easier said than done in practicality, but it's usually my goal. It probably helps that I often prefer to shoot wide- or nearly wide-open (f/1.3 or maybe f/2), so that makes it a little easier.

T2

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



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Richard Herd
Re: Question about exposure settings
on Aug 16, 2016 at 9:08:30 pm

[Todd Terry] "choose f-stops for the desired depth of field, and then light (and filter and sometimes even adjust ISOs) accordingly to expose properly"

This is exactly what I try to do, although I do not much like changing ISO for the same scene because I feel it changes the image: maybe adding some contrast slightly -- like moving from 320T to 800T. I think once Mr. Sweden gets the idea of contrast ratio (really latitude, I know, but I think this idea of "you only get 5 f/stops" as a ratio of light to dark is a good way to think about it), he can light for the f/stop. Might take a bit longer the first couple of times but worth figuring out.

Maybe "whole f/stops" was stated incorrectly/too quickly. The answer to why is because I'm old and set in my ways. There is no art to it :)

I still use a Sekonic L-398A incident meter and it marks the f/stops as 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16. It does have the splits. LOL! Sorry it's not fancy and pretty banal.

One quick real-world example: I recently shot an interior day, and the outdoor was fortunately very cloudy, so I measured outside at a 5.6-8 split and I figured the clouds would move here and there.

In my head I thought "okay it's a 5.6"" because it would expose for the redwood trees just outside the window. Interior, the keylight at 2.8 -- which made any burned out dapple look kind of nice.


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