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Making darks darker


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#1 Christopher Norin

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Posted 22 December 2009 - 04:57 PM

I've shot HDV material with a Sony HDR Z1 camera, and captured it as such into FCP 7. The material is shot during the day with no lights and at night using only a camera lamp or natural light such as street lamps. My main concern is grain. The image overall is grainy but the darker more than the brighter.

It might be too late for this material (might be something I can do with color correcting but that is beside this post) but how would I go about reducing the probability of grain when shooting? The first thing to do I guess, is to shoot with a better camera, but my question concerns more then lighting of dark areas. I've heard this before, but it somehow eludes me how one lights the darks to make it darker. I do understand that low light conditions make for an overall grainy and greyish image, but how would you improve the darks by pouring in light into it? Okay, you expose for 2 stops over, as more light is generally good, but will that make the darks darker immediately or is this something assumed to be "fixed" in post (don't cringe). The one example I can come up with now is Cinematoggraphy Style, the part with Vittorio Storaro in a dark room with only a bulb as illumination. The darks are not grainy at all. Has this to do with format, camera, or lighting?

Again, is it so that darks get darker with more light?

I want to add that I've been involved with filmmaking as a director on several shorts, produced on video, 16mm and 35mm. I do have a basic understandning of lighting a set, but as I'm moving into cinemtography I will need to educate myself on lighting.
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#2 David Rakoczy

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Posted 22 December 2009 - 05:30 PM

You create blacker blacks by lighting brighter to create contrast. Instead of lighting your talent to say a 2 or 2.8, you light to a 4, 5.6 or 8 etc to create a greater difference in what is lit from what is not. This creates more contrast.

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#3 David Mullen ASC

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Posted 22 December 2009 - 06:56 PM

You have to mentally separate two issues: one is how black are your blacks, and the other is how much shadow detail do you want. They are related only in the sense that if you "crush" the blacks in post to make them darker, you also lose shadow detail -- hence the idea of adding more light into your shadows. It's not because more light in the shadows makes them darker, which is ridiculous, but it gives you the flexibility of making the blacks deeper while still retaining some shadow detail so they don't look too plugged-up artificially.

But if you want a pitch-black shadow, you don't add more light to it. However, as David said, blacks look richer and darker in contrast to a bright highlight, so make sure you have enough contrast in your lighting and you have a good exposure for your highlights.
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#4 Christopher Norin

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Posted 23 December 2009 - 05:37 AM

I appreciate your feedback. Both educational.

My problem is that the blacks I've got are very grainy and grayish (as a result of the grain I guess). Would creating higher contrasts by a slight overexposure help on this specific problem? Or is the grain something I have to live with when I shoot with the Z1, a camera at the losers end of semi professional cameras?

I'm not completely sure what crushing the blacks mean but I think I get the picture, I've heard the concept before. Does it mean that I overexpose my dark areas a bit and then make then darker ("crush") in post.

Thanks again, and merry christmas!

Christopher
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#5 David Mullen ASC

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Posted 23 December 2009 - 11:30 AM

I appreciate your feedback. Both educational.

My problem is that the blacks I've got are very grainy and grayish (as a result of the grain I guess). Would creating higher contrasts by a slight overexposure help on this specific problem? Or is the grain something I have to live with when I shoot with the Z1, a camera at the losers end of semi professional cameras?

I'm not completely sure what crushing the blacks mean but I think I get the picture, I've heard the concept before. Does it mean that I overexpose my dark areas a bit and then make then darker ("crush") in post.

Thanks again, and merry christmas!

Christopher


"Crushing the black" just means color-correcting the image so that the blacks are pushed down to "0" on a waveform. Technically, when you start squashing shadow detail too you are "crushing" the image. Setting black at "0" would take care of the greyishness.

The question about the noise (not grain, grain is a film term) just depends on whether the noise appeared because the camera automatically boost gain in low light or whether it is inherently noisy. For example, if you took the camera outside in daylight, is it still noisy? If yes, it's a noisy camera. If not, it means that some sort of auto-gain is happening once the light level drops below a certain point. One trick then is to make sure that the auto-gain is off and shutter and f-stop are set manually. Then you'll find out if you really had enough light to shoot under without gain. So it's not so much that you need to overexpose, it's that you need enough light that the camera doesn't start boosting gain to compensate. With a lot of these cameras, once the auto-iris hits the wide-open position, gain is boosted automatically to compensate. So if you turn-off auto-gain, and set the shutter and iris manually to, let's say, f/2.8 and 1/50th, and your monitor picture is very dark, it means you need to increase the light level.

Try again using a lot more light level and see if the noise stays the same or not.
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#6 Christopher Norin

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Posted 23 December 2009 - 11:36 AM

"Crushing the black" just means color-correcting the image so that the blacks are pushed down to "0" on a waveform. Technically, when you start squashing shadow detail too you are "crushing" the image. Setting black at "0" would take care of the greyishness.

The question about the noise (not grain, grain is a film term) just depends o n whether the noise appeared because the camera automatically boost gain in low light or whether it is inherently noisy. For example, if you took the camera outside in daylight, is it still noisy? If yes, it's a noisy camera. If not, it means that some sort of auto-gain is happening once the light level drops below a certain point. One trick then is to make sure that the auto-gain is off and shutter and f-stop are set manually. Then you'll find out if you really had enough light to shoot under without gain. So it's not so much that you need to overexpose, it's that you need enough light that the camera doesn't start boosting gain to compensate. With a lot of these cameras, once the auto-iris hits the wide-open position, gain is boosted automatically to compensate. So if you turn-off auto-gain, and set the shutter and iris manually to, let's say, f/2.8 and 1/50th, and your monitor picture is very dark, it means you need to increase the light level.

Try again using a lot more light level and see if the noise stays the same or not.


Eye opening. Thanks a lot.

I'm planning lightingworkshop for myself, to happen in the near future. I will certainly play around with blacks and your advice on how to handle it.
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#7 John Sprung

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Posted 23 December 2009 - 06:33 PM

Crushing the blacks in post crushes everything in the low end equally. There's no way to distinguish between real world shadow detail, electronic noise, or film grain from telecine -- unless you have power windows avaliable, but still that means doing it "by hand" shot by shot. So, if you don't need or don't want the real detail in that range, crush away and get rid of the noise/grain, too.

Post is the right place to crush stuff, because you can change your mind based on how it looks all cut together. If you crush the blacks in camera, you're SOL on ever getting anything back.

(Edit: Oh, of course, there are overall degraining and re-graining software programs such as Arri Relativity, but these are mega-pricey, not widely available.)





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#8 Steve London

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Posted 24 December 2009 - 01:37 PM

Where do you look at images in electronic format to judge the blacks? What display is capable of showing black? My computer can't do it. A broadcast quality CRT, maybe? I really love the looks of movies on my (calibrated with probe and software) 52" Vizio but when the screen goes to "black" in a darkened room I see that it is 1.) not perfectly uniform and 2.) dark grey not black.
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#9 John Sprung

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Posted 24 December 2009 - 04:09 PM

A broadcast quality CRT, maybe?


That's been our answer for decades, but the last CRT plant that made them closed a while back. The last old-stock Sony BVM CRT has been sold. There aren't any more. For the future, there seem to be two answers out of three:

1. For high end work, DLP front projection. This takes a big room and has a big pricetag, but for big features, it's the way to go.

2. For typical post facility bays, consumer plasma displays with a correction box ahead of them. These would be set up using test patterns and a probe to match quite well with the venerable CRT's.

3. LCD broadcast monitors. This was the first idea we saw under development, but so far, they don't look like they'll be as cost effective as the plasma-plus-box. The early ones have viewing angle problems that limit them to single user workstations.




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