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Checking if there is noise in your picture with scopes

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Lili Chin
Checking if there is noise in your picture with scopes
on Jun 13, 2015 at 6:35:35 pm

Hi, I have a simple question. I am trying to color correct some footage that was transfered at a post house from Super 8 to Apple Pro Res 444. They did a terrible job and I am experimenting with color correcting the footage. I need to lift the gain tremendously and adjust the gamma. How do I read the scope and tell if I am going too far and inserting noise . Ie. how can I look at a scope (waveform/ vetor/ parade/ histogram) and read if there is noise in the image. The only way I know is if I drop the saturation to 0 and look at the vector to see if there are any dancing pixels, but I think that may be wrong. There must be a way, this is a specific question for colorists who do telecine from film to video...

thanks so much

Lili


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Joseph Owens
Re: Checking if there is noise in your picture with scopes
on Jun 13, 2015 at 8:48:57 pm

[Lili Chin] "How do I read the scope and tell if I am going too far and inserting noise . Ie. how can I look at a scope (waveform/ vetor/ parade/ histogram) and read if there is noise in the image. The only way I know is if I drop the saturation to 0 and look at the vector to see if there are any dancing pixels,"

First of all there is a big difference between "noise" and "grain"... and both will be present in your image.

If you are cranking the image up by more than a stop or so, you will be compromising the picture integrity no matter what you do. Scopes (waveform and vectorscope) don't really have a specific "noise" or "grain" measuring function -- what you need to use is your judgement interpreting how "granular" the traces become. Modern software enhancement in the digital domain is very clean. You are unlikely to be "introducing" noise -- what is probably the case is that your grade is amplifying a very large grain signature that is inherent in the original image. Super8 is an extremely tiny image to be blown up to anything more than SD and it would take a very capable scan to get it into HD or beyond. I expect its also reversal, so -- dense to start with.

Its always worth a try, to contact the transfer facility and just hang it again to make sure everything that was in the emulsion made it out of the machine.

Otherwise, you will be into Noise Reduction.

jPo

"I always pass on free advice -- its never of any use to me" Oscar Wilde.


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David Roth Weiss
Re: Checking if there is noise in your picture with scopes
on Jun 13, 2015 at 10:13:58 pm

Lili, why don't you export a frame and post it here? You're bound to get a much more informed and helpful response.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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Lili Chin
Re: Checking if there is noise in your picture with scopes
on Jun 28, 2015 at 4:17:17 am
Last Edited By Lili Chin on Jun 28, 2015 at 4:22:02 am

Dear All,
I don't know if this thread will continue, but I have some images here -

8981_sonofmancomparison.png.zip

please see attached. I am wondering how I can read the scopes on my Da Vinci resolve to see if the telecine colorist who transfered my b+w 16mm negative did something wrong. The first transfer on the left you see a flat scan - he didn't set the black and white levels and that's why it looks so grey. Then he took that scan and set the blacks and whites 'properly' but all of a sudden it has a lot of black particles that look like dancing noise when I play it - the transfer is from 16mm to 2K. This project will eventually go back to film and is also a remastering to have a high resolution video transfer from my 16mm film. I actually think the flat scan looks better than his color timing. Can you let me know how I can look at the scopes on da vinci and see if he accidentally pressed a button to put noise in the picture? When I look at the 16mm print, the film doesn't have those dancing particles. I know it was shot on film that was fogged and a little over exposed but his color corrected transfer looks pretty bad to me. Can anyone help with an opinion?


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David Roth Weiss
Re: Checking if there is noise in your picture with scopes
on Jun 29, 2015 at 8:59:52 pm

Lili,

What you're seeing is film grain... This looks like it was shot on Tri-X reversal, which was hi-speed (400 ASA) film stock, which is inherently very grainy, but which is now looking MUCH more grainy because your scaling it up by about 400%.

FYI. the grain is there in the low contrast version, you just can't see it... If you want to minimize the grin you can use a Noise reduction app such as Neat Video or the one in the full ($1000) version of Resolve.

David Roth Weiss
Director/Editor/Colorist
David Weiss Productions


David is a Creative COW contributing editor and a forum host of the Apple Final Cut Pro forum.


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Marc Wielage
Re: Checking if there is noise in your picture with scopes
on Jun 30, 2015 at 1:37:38 am

I think if they set DMIN and DMAX in the scanner to something a little closer to the way it should look -- but still in log space -- it will have less grain. Super 8mm PlusX or 4X negative is pretty rare and I suspect will be extremely grainy no matter what. But I suspect the scan could be better.


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