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Log and negative film stock


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#1 Daniel Meier

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Posted 05 April 2016 - 05:26 AM

Hi there.

Just a general question that arose yesterday. As I never worked with negative film stock before.

What does negative film (35mm, 16mm) look like, when coming straigh out of the lab. Is it as flat looking as nowadays digital Log footage?

 

 


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#2 Mark Dunn

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Posted 05 April 2016 - 05:34 AM

Out of the lab it looks like a strip of orange plastic unless you're having a workprint, in which case it hopefully looks quite a bit like the scene you've photographed.

Do you mean after scanning?


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#3 Daniel Meier

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Posted 05 April 2016 - 06:37 AM

Sorry, I don't have that much of an idea.

 

Let's say at the point where the editors are doing their first rough cuts.

Maybe someone could post a sample frame.

 

Me and my workmate were just wondering if the flat look of a log image is just an invention of the digital age.

He said that e.g. the Canon C300 puts out images that look more similar to film stock than the S-Log2 image of a FS 700, because the C300's image is not as flat.


Edited by Daniel Meier, 05 April 2016 - 06:39 AM.

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#4 Brian Drysdale

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Posted 05 April 2016 - 07:33 AM

All these log curves etc are to match film. The gamma of film neg is lower than that of a projection contrast print. This is a rough example:

 

http://www.camerapos...nsFilmCurve.jpg


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#5 Mark Dunn

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Posted 05 April 2016 - 09:59 AM

Oh dear. That graph is terribly misleading, not to say wrong. No units.. The response doesn't cut off like that. The reversal curve should be the other way around- density goes down with exposure, not up.


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#6 Brian Drysdale

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Posted 05 April 2016 - 10:12 AM

True, I was more  comparing shapes, it's rather simplified ,


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#7 Tyler Purcell

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Posted 05 April 2016 - 12:06 PM

Me and my workmate were just wondering if the flat look of a log image is just an invention of the digital age.


Umm yes.. it is an invention of the digital age, specifically MPEG cameras. WHY? Because MPEG in of itself is a compressed color space format. It's designed to record REC 709 color space, no more. Plus, only a hand-full of them record 10 bit 4:2:2, which is still a format missing quite a bit of image data. So it's REC 709 mixed with 10 bit 4:2:2, which are actually the standards for broadcast and have nothing to do with cinema (12 bit 4:4:4) quality. In order to compress a fuller bandwidth signal into the REC 709 color space, MPEG based cameras have created a "FAUX" Raw format called S-Log. With that said, you will never recover the missing data unless you record in 4k and scale down to 2k, which fills in the missing color information, but doesn't change the bit depth.

By contrast, Red, Arri and Blackmagic, record to uncompressed AND compressed RAW formats, ranging from 12 - 16 bit, depending on which flavor. Camera RAW is very unique because it takes the imager data without the Debayer layer and records it. This allows for the debayer process to be done in software, which allows FAR more control over the color correction. This is part of the reason you see almost every feature film today using RED and ARRI cameras. As a side note, the only non-RAW codec that allows full bandwidth is Pro Res XQ, which is a 12 bit 444 codec, but does the Debayer in camera. Arri and Blackmagic have focused on using this codec as an alternative to RAW. What humors me is that RED and Sony have tried to jump on the Pro Res bandwagon, but as this writing, they use Pro Res to save space, so they only have the lower-end codec's.

Film negative has full dynamic range already in it. Yes, it's a bit flatter then a print for instance, but it's not like S-Log or camera RAW which can be extremely flat.
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#8 Robin R Probyn

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Posted 05 April 2016 - 04:54 PM

More wrong info from Tyler  come on really please study up n this.. you are always giving out dud info man.:).. Slog is NOT RAW. or ever claimed to be .its a log curve..as in S LOG !! in fact Slog3 is almost exactly the same as Arri LogC.. F5/55 can record 16 bit RAW..

 

It has nothing to do with MPEG..

 

"Canon C300 puts out images that look more similar to film stock than the S-Log2 image of a FS 700, because the C300's image is not as flat."

 

The canon C300 C Log is a rather compromised Log curve.. due to the 8 bit max of that camera.. its more like a hyper gamma curve from a Sony camera.. Sony Slog is more of a "true" log curve ..has more DR than C Log.. and so when un corrected appears alot more flat,un saturated than the C300 "log" footage


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#9 Tim Tyler

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Posted 05 April 2016 - 05:32 PM

Tyler says that S-log is flatter than film negative, not that S-Log = RAW.

 

More wrong info from Tyler  come on really please study up n this.. you are always giving out dud info man. :).. Slog is NOT RAW. or ever claimed to be


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#10 David Mullen ASC

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Posted 05 April 2016 - 05:42 PM

A Cineon log scan of film negative looks very flat on a Rec.709 monitor, very similar to ARRI Log-C.
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#11 Tyler Purcell

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Posted 05 April 2016 - 06:10 PM

Slog is NOT RAW. or ever claimed to be .its a log curve..as in S LOG !! in fact Slog3 is almost exactly the same as Arri LogC.. F5/55 can record 16 bit RAW..


That's right and nowhere did I say slog is raw. The word "faux" means fake.

Slog was developed specifically for cameras that don't record raw and record to rec709. If you shoot raw you don't need slog curve, it's irrelevant in fact.

Ohh and we've already had discussions on cameras that need special hardware to record properly. Most people won't invest unless it's necessary. In the case of the OPs question, film has no relationship to camera raw or slog.
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#12 Satsuki Murashige

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Posted 05 April 2016 - 08:00 PM

Umm yes.. it is an invention of the digital age, specifically MPEG cameras.


No. Log was created as a means of capturing the full dynamic range of the negative in a film scan to the Kodak Cineon format. It is directly analogous to the film negative. Arri created Log-C for their digital cameras to emulate Cineon/DPX film scans based on experience with their film scanners, which is why the Alexa looks similar to scanned Kodak color negative.

Log has nothing to do with mpeg, don't know where that idea came from.

https://en.m.wikipedia.org/wiki/Cineon
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#13 Adrian Sierkowski

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Posted 05 April 2016 - 08:34 PM

I thought that the Cineon stuff was Lin not Log though? Or was it just that there was an option for Lin with Cineon?


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#14 Tyler Purcell

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Posted 05 April 2016 - 09:28 PM

Log has nothing to do with mpeg, don't know where that idea came from.


The whole reason LOG was created is to keep a certain look from scan through projection. They wanted something that mimic's film's dynamic range and color space, to create a "digital negative".

S-Log is designed to optimize the noise floor and tonal reproduction of the imager and compress it into a data packet which will work within the limited Rec 709 codec's.

S-Log is a SONY format, which took off because vendors picked up on the idea to be compatible with Sony cameras. If Sony cameras recorded RAW, there would be no reason for their own S-Log system. However, until very recently, Sony cameras didn't record RAW, so it's clear their whole intention from the get go was to solve a HUGE problem their cameras had. If you have a limited dynamic range REC 709 RECORDING format, how do you squeeze high dynamic range material into it? You simply compress the dynamic range and expand it in post. Same philosophy as analog audio tape noise reduction.

You will notice, S-Log is used on cameras that shoot MPEG. Cameras that DON'T shoot MPEG... Arri, RED, Blackmagic, AJA, don't have S-Log because they don't need it.
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#15 Stuart Brereton

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Posted 05 April 2016 - 09:34 PM

Arri, RED, Blackmagic, AJA, don't have S-Log because they don't need it.

 

S Log is just Sony's name for their version of the LOG curve. Arri don't have S Log, because they have Log C, as Canon have C-Log, Blackmagic has Film Gamma and Aja has Expanded Gamma. All just different versions of the same thing, tweaked to suit the dynamic range and response of the cameras.


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#16 Tyler Purcell

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Posted 05 April 2016 - 10:18 PM

S Log is just Sony's name for their version of the LOG curve. Arri don't have S Log, because they have Log C, as Canon have C-Log, Blackmagic has Film Gamma and Aja has Expanded Gamma. All just different versions of the same thing, tweaked to suit the dynamic range and response of the cameras.


That's one way to look at it. I see it as a compromise for the lack of a decent recording format.
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#17 David Mullen ASC

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Posted 05 April 2016 - 10:46 PM

Log has nothing to do with MPEG compression -- after all, a 10-bit Cineon Log scan of film negative is recorded to uncompressed DPX files.

 

One could say, however, that Log is a method of more efficiently storing a wide dynamic range from a digital sensor into 10-bits, 12-bits, etc.  However, if we start getting into 16-bit recording such as RAW recording for the Sony F65 or the whole ACES workflow, then it is possible to work in linear gamma without worrying so much about wasted bits.

 

But compression is a whole separate issue. The S-Log gamma has nothing to do with whether it is recorded to MPEG or not.  In theory you could shoot and record 16-bit RAW on a Sony F65 and convert it in post to S-Log gamma but stored as 10-bit uncompressed DPX files.

 

You often record Log-C on an Alexa to ProRes, which is another DCT-varient similar to MPEG.


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#18 Tyler Purcell

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Posted 05 April 2016 - 10:58 PM

Right, but again it exists because of the inferiority of the storage format.

If the storage medium was 24 bit RAW directly off the imager with zero processing, there would be no reason for S-Log.

Sony and Canon's incessant use of antiquated 8 bit 4:2:0 Rec 709 color space recording formats are EXACTLY the reason we have S-log.
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#19 Stuart Brereton

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Posted 05 April 2016 - 11:04 PM

Sony and Canon's incessant use of antiquated 8 bit 4:2:0 Rec 709 color space recording formats are EXACTLY the reason we have S-log.

 

You seem to be using S-Log as a generic term for Log Gamma, whereas it's actually the name of Sony's own implementation of a Log Curve


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#20 Stuart Brereton

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Posted 05 April 2016 - 11:07 PM

That's one way to look at it. I see it as a compromise for the lack of a decent recording format.

Are you saying that Pro Res 444 is NOT a decent recording format?


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