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THE DARK SIDE (shadows and avoiding grain)


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#1 Grant Fergus

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Posted 20 November 2010 - 06:23 AM

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Hey Guys,

I've just posted 3 images which hopefully worked ok. I think they get posted above, but let me know if there are any probs and I'll try posting them as links instead.

They are screen grabs form the film:

Love Me If You Dare

http://www.imdb.com/title/tt0364517/


The pictures show actor Guillaume Canet as he walks from light into a Silohuette. As it shows in the pictures, this set is lit with a lot of contrasting dark and light areas.
There are bright pools of light and areas that are essentially pitch black.

I really love the idea of playing with light in this way, but wondered how you go about doing it?

And how do you avoid grain in the really dark regions when shooting on digital...

Is it a case of having everything lit accordingly and then closing the iris until the areas with less light become very very dark?

(and what would be the lighting plan for getting pools of light like this....)

I guess it varies from camera to camera, but I'm quite interested in understanding how dark things can actually be and how to go about creating low grain dark areas when shooting on digital.

Also :)

I notice in the top picture (wide shot) that the surrounding walls are catching just enough light to give them definition and let you know there are actually walls there, but in the other two closer shots ie over his shoulder in the light and silhouetted mid shot from behind, the surrounding walls are much brighter...

Was also wondering if people had any thoughts on that, would the wider shot be lit differently or is it that the wider shot is responding differently to the same lighting setup etc...


Questions questions, :rolleyes:

thanks in advance for any insight

Grant :)

Edited by cineman, 20 November 2010 - 06:26 AM.

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#2 Brian Drysdale

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Posted 20 November 2010 - 11:44 AM

You need to use your real name, it's one of the forum rules.
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#3 Grant Fergus

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Posted 20 November 2010 - 01:48 PM

You need to use your real name, it's one of the forum rules.



Thanks Brian, I wasn't aware of that, that's my display name changed.

Any thoughts on the questions and pictures above?

Grant :)
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#4 David Mullen ASC

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Posted 20 November 2010 - 06:18 PM

There really isn't a "trick" to avoiding digital noise or film grain in the shadows. It's mainly an issue of base exposure (not necessarily meaning add more light to shadows, though sometimes that gives you more flexibility later in post).

You have to ignore the idea of the moody shot for a moment and think about the technical issue, which is how much noise or grain do you see in a pure black, a middle grey, and/or a pure white field -- i.e. what is the "base" level of noise or grain. I'm skipping the issue of chroma noise for a moment, which is really an issue of noise in individual channels, or with film, in the individual layers.

There is an overall level of noise or grain to the image, sort of part of the basic design of the camera, sensor, recorder, codec, etc. and in the case of film, with the film stock. It's hard to get much quieter or less grainy than that inherent base. I mean, with digital you could go to negative gain on some cameras, but there will be a certain level that is just part of the system, so the first thing is to choose a digital camera, film stock, etc. that has the general level of noise or grain you can live with.

So after that, it's mainly an issue of avoiding making it worse, increasing the apparent noise or grain.

And that mainly depends on how much you push the image up or down in timing / color-correction. Underexposed images brought up get noisier / grainier; overexposed images brought down generally (though not always) get cleaner, less grainy-looking.

If you took an unexposed roll of film negative and developed it normally, you'd have more or less a blank / clear piece of negative other than the base fog level, no image at all. Printed, it would be a black image. So take that negative and print it in the 10's, 20's, 30's, 40's, and 50's (top of the scale) and you find that the blacks in the print look deeper when the printer light numbers are higher. So a darkly-lit scene would have less grain, deeper blacks, etc. if the printer lights used to make the correct exposure for the look you wanted were higher, above 30.

Same goes for electronic timing more or less, as you bring down or up the black level, or the overall image, the noise gets better or worse.

So the problem isn't having dim areas in the frame -- you could have someone standing against a black curtain if you wanted to, it won't necessarily look noisy. The issue is the overall signal strength and how you push it around in color-timing.

So light the scene however you want it to look in terms of key to fill level, just make sure that your base exposure, your overall exposure, your key, whatever, is exposed well enough that you won't be trying to lift up anything in the frame in post. If anything, it will get cleaner if you push it down, darker. This is one aspect that may affect your lighting... if you decide you prefer the look of slightly crushed blacks, then you may want slightly lighter shadows, a bit more fill, so that once you push things down, you retain some detail in the shadows. In other words, if your image is slightly less contrasty and you add a bit more contrast in post, and darken the blacks, the image in general will seem cleaner, less noisy.

So basically you have to separate the issue of how dark the image looks on the set, and how dark it will look in the final version, from how dark you expose it. You create the image that you want, but you make sure that your recording has enough overall level of exposure so that there is no chance that you will be lifting anything up in post.

Sometimes the example of the darkly-lit frame from a movie is confusing -- a frame is just a series of tonal and color values, so just shoot a grey scale and a color chart and see how visible the noise is in different patches or stripes. And shoot the charts at different base ASA levels to see how that affects noise.

In that example above, the same shot with the same lighting could have been exposed at different base levels and given you different amounts of noise or grain.
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#5 Grant Fergus

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Posted 20 November 2010 - 07:02 PM

Thanks David, I couldn't really ask for a more comprehensive and knowledgeable response than you gave, I'll go back and read it a few times and you gave me a lot to think about and clarified a lot of things for me.


:)
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#6 Grant Fergus

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Posted 21 November 2010 - 08:45 AM

a frame is just a series of tonal and color values, so just shoot a grey scale and a color chart and see how visible the noise is in different patches or stripes. And shoot the charts at different base ASA levels to see how that affects noise.

In that example above, the same shot with the same lighting could have been exposed at different base levels and given you different amounts of noise or grain.






"cameras are usually calibrated so they give the best image quality at their lowest ISO"

I've heard a lot of people talk about using different ISO settings at the same FStop and noticing different level of grain and this often seems to be a decision made while engaged in a night shoot.

Not sure exactly where ASA fits into everything but I'll look into it more. Here's an article that talks about ASA and also using a" 18% Gray Card" which I think is the same as the greyscale chart you were talking about.

Where do light meters fit into all of this ? :)

Grant :)

http://www.digitalci... HD Cameras ASA
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#7 David Mullen ASC

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Posted 21 November 2010 - 01:12 PM

"Best" is somewhat subjective -- in general with digital cameras, you have sort of a base sensitivity but really how you expose an image depends on whether you are worried more about noise versus clipping of highlight detail. Give the digital camera a low rating and you have less noise but more chance of clipping bright areas; give it a high rating and you get more noise but less clipping. So what's "best" depends on the look you want -- most people go for a happy medium.

Now I'm talking mainly about RAW cameras and to some extent LOG cameras... cameras designed to record the maximum dynamic range of the sensor onto a low-contrast recording which will be color-corrected later. So how you expose, what ASA you use, depends on how you want information to be captured for use later.

The article by Sean is mainly about Rec. 709 broadcast cameras where black is 0 IRE, white is 100 IRE (sometimes a bit over) and 18% grey is around 45 IRE on a waveform monitor. If you follow that, you can determine the general "ASA" of the camera by pointing the camera at an 18% grey card. With LOG cameras, white on a grey scale (Zone 10 I guess) may be designed to fall at 70 IRE in order for the camera to capture "super whites", overexposed detail above normal white, which we have a lot of in real life. Which is why a LOG image seen on a Rec. 709 monitor can look a bit murky unless a LUT is applied to the signal to correct the contrast (gamma) for the display.

With a RAW camera like the RED, you could just point the camera at an 11-step chip cart (two rows of grey scales, the bottom one going in the opposite direction, which creates an X shape on a waveform) and just set the f-stop until the crossover point is in the middle, meaning you have weighted the exposure equally for highlights and shadows. In RAWVIEW, you'd probably find that you were around 320 or 400 ASA with the new M-X sensor. So that's close to what you'd call the "true" sensitivity or ASA of the sensor.

However, as I said, you base an ASA on a balance between noise and clipping. When you have a less-noisy sensor / camera like the M-X Red One, then you have more freedom to choose a higher ASA and get better highlight retention at the expense of very little noise, which is why most people are rating the M-X Red One at 800 ASA -- it's the optimal balance between noise and clipping. But 400 ASA would be even lower in noise.

ASA is a bit of a confusing issue to apply to digital cameras. You basically have to factor in the extreme ends where things get clipped or crushed when factoring in the final exposure. Mainly because, unlike with film, there is less overexposure protection.
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#8 zachary holloran

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Posted 03 January 2011 - 02:33 AM

David,

I really enjoyed reading about what you had to say about lighting for dark areas. I'm shooting on the RED One with a 320 ASA and was wondering how many stops I had to work with as far as shadows and dropping to black. I understand that my base will need to light even parts that will be crushed in post, but how many stops below the key should my base be with a 320 ASA? And what does IRE stand for?

Anyway, I'd appreciate any further assistance in this matter - thanks guys :)

z
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#9 David Mullen ASC

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Posted 03 January 2011 - 02:47 AM

David,

I really enjoyed reading about what you had to say about lighting for dark areas. I'm shooting on the RED One with a 320 ASA and was wondering how many stops I had to work with as far as shadows and dropping to black. I understand that my base will need to light even parts that will be crushed in post, but how many stops below the key should my base be with a 320 ASA? And what does IRE stand for?

Anyway, I'd appreciate any further assistance in this matter - thanks guys :)

z


You're shooting digital, surely you can see on a monitor when things are going black? Plus with Red footage, you can look at a single converted 4K TIFF of a frame and study that on your computer later. Shoot either an over / underexposure test (grey scale shot normal, -1 stop, -2 stop, etc.) or shoot a contrast ratio test (fill side -1 stop, -2 stop, etc.) and then look at the frame in Photoshop, play around with the black level until you like it, and that should tell you roughly how dark to light a shadow and still see detail before it goes black.

http://en.wikipedia.org/wiki/IRE_(unit)
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#10 zachary holloran

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Posted 19 January 2011 - 01:34 PM

You're shooting digital, surely you can see on a monitor when things are going black? Plus with Red footage, you can look at a single converted 4K TIFF of a frame and study that on your computer later. Shoot either an over / underexposure test (grey scale shot normal, -1 stop, -2 stop, etc.) or shoot a contrast ratio test (fill side -1 stop, -2 stop, etc.) and then look at the frame in Photoshop, play around with the black level until you like it, and that should tell you roughly how dark to light a shadow and still see detail before it goes black.

http://en.wikipedia.org/wiki/IRE_(unit)



Thank you so much David. This helps a lot. I'm glad there are guys out there like you who help the little guy :)
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