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how can I control HD noise


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#1 Crell Lee

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Posted 05 April 2009 - 10:31 AM

in hd video there are too much noise in shawdow, and how to reduce it ? how can i control in shooting and get real black? what about post control
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#2 Adrian Sierkowski

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Posted 05 April 2009 - 10:42 AM

You can crush the blacks either in camera, in some cameras, or in post.
Also make sure your Gain is down at 0dB or -3dB.
Also, you must use your real first and last name to post here.. Please go to "my controls," and then "change display name" on the upper right, then middle left hand sides of the screen respectively.
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#3 DavidFu

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Posted 05 May 2009 - 11:14 AM

You can crush the blacks either in camera, in some cameras, or in post.
Also make sure your Gain is down at 0dB or -3dB.
Also, you must use your real first and last name to post here.. Please go to "my controls," and then "change display name" on the upper right, then middle left hand sides of the screen respectively.


Noise is a problem on any digital camera, it is a fact of the format at this time. David Fincher had denoising worked into his workflow on Benjamin Button shooting with the Viper. The only perfect solution is to denoise in post and that can pretty expensive if done by a specialist.
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#4 Joe Giambrone

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Posted 13 May 2009 - 12:00 AM

I do know that sensors are rated for a particular color temperature. Find out what it is and only give it that color white. This will reduce noise, particularly in the blue channel if you are giving it tungsten light (3200K), when the sensor is balanced for daylight (5000-5500K).

Something to look into.
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#5 Satsuki Murashige

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Posted 13 May 2009 - 04:48 AM

in hd video there are too much noise in shadow...

What is your experience with HD cameras?

Have you only used prosumer cameras like the small sensor HVX200, EX1, etc.? Have you used low-end 2/3" chip cameras like the HPX500? Mid and hi-end 2/3" cameras like the F900, Varicam, F23, etc.? 35mm sensor-size digital cinema cameras like Red, F35, Genesis? There's a whole range of HD cameras out there, many of which are very capable of producing clean images.

In general, the larger the sensor, the better the signal to noise ratio. So larger chips will usually produce less noise than smaller chips under equal lighting conditions. Higher end cameras have better sensors and better processing in-camera to maximize the information coming off the sensor, and they record to less compressed codecs, resulting in a cleaner image. Beyond that, it's up to the DP to light well.

Several problems often come up with beginning shooters: one, not lighting to a sufficient light level to expose properly; two, using a low contrast gamma setting like the HVX's "Cine D" without color correcting properly in post. One is often compounded by the other.

The less light the sensor gets, the more noise it produces instead of signal. That's just the nature of video sensors. So you want to be conservative with exposure - light brighter and with lower contrast than you want it to look. This ensures that you are capturing as much signal as possible and therefore as little noise as possible. Darken and increase contrast in the color correction process at the end of post production.

With low-con gamma settings, the image you are looking at has raised midtones, raised shadows, and lowered highlights to show you the maximum highlight and shadow information off the sensor. However, the shadow info is not all usable - it becomes increasingly noisy as the tones get darker. The idea is to leave the decision of how much shadow detail is usable and how much should be pushed down into pure black to post production and not to production.
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#6 Alexander Disenhof

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Posted 14 May 2009 - 01:48 PM

"two, using a low contrast gamma setting like the HVX's "Cine D" without color correcting properly in post"

Hi Satsuki - could you elaborate on the process of color correcting for the "Cine D" setting? Or could you refer me to an article/any information about it? Thanks!

Alex Disenhof
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#7 Charles Son

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Posted 17 June 2009 - 06:23 PM

"two, using a low contrast gamma setting like the HVX's "Cine D" without color correcting properly in post"

Hi Satsuki - could you elaborate on the process of color correcting for the "Cine D" setting? Or could you refer me to an article/any information about it? Thanks!

Alex Disenhof

I've been using the Cine D for awhile now on the HPX500 (the HVX's big brother) and it works out very nicely. You've got to change around some of the other settings, especially the pedestal. It's almost like getting a flat pass at a telecine, giving you control of contrast in post. All you do is crush the blacks in post as much as you want.

The Cine D setting is most useful, for me, when I want to grab more information in the blacks and lower midtones while still keeping the highlights decently exposed. In effect, it increases the poor dynamic range of video.

Check out "hunter's settings" for the 500 here:

http://www.dvxuser.c...ad.php?t=119457

Unfortunately, the HVX200 is much noisier in the blacks than the HPX500...
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#8 Phil Rhodes

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Posted 17 June 2009 - 08:20 PM

The HVX200 is extremely noisy, the problem being exacerbated by the fact that it's a fairly low res camera so the noise artifacts are large compared to the image. Actually Viper is pretty noisy, too, but that impression probably stems from watching uncorrected log output on a linear monitor, which has broadly speaking the same effect as using some of these ultra low-contrast curves on other cameras.

This is, however, I think, mainly a philosophical discussion.

In video you have the stark choice between nice highlights and noisy shadows, or nice shadows and clipped highlights. Noise floor effectively determines the dynamic range of the camera, and most of them give you enough control to pick what you want within a stop or three. All the low-con curves do is allow you to consider shadow detail to be more mainstream image detail, in effect normalising an image that as far as the sensor is concerned is two or more stops under. You've closed down, so you get nicer highlights, at the expense of using noisier shadow data in more visible luminance ranges of the image.

Take your pick. Personally I massively perfer noise to nasty highlights.

P
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#9 Paul Bruening

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Posted 18 June 2009 - 08:13 AM

I'm always a little bit smarter after your posts, Phil. Thanks.
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