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#1 Murali Pallikonda

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Posted 10 May 2009 - 10:18 PM

Hi,

This might be a dumb question. Every time I see raw footage shot with Red One, this pops in to my mind.

I understand that, Color temperature difference is one of the culprits (Camera is set at 5600 while scene is at a different temperature). Exposure, even though we set it properly, image looks as if it is over exposed. Are there any other factors in play here ?

Thanks in advance,
Murali
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#2 Chris Durham

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Posted 11 May 2009 - 11:52 AM

As a Red question this probably belongs in the Red or at least the HD forum.

The desaturated look is by design. The Red is designed for a post-intensive workflow which favors a neutral image. Most video cameras without a raw workflow, or in fact film cameras with the characteristic curve of a particular stock, aren't a pure expression of captured light. Typically sensor data is interpreted and then gamma-encoded and defined within a color space. This information is burned in to the image.

With a raw image you basically have what was captured at the sensor, and because it's raw you have a lot of detail to manipulate. With an encoded image, when you grade, you're manipulating pre-manipulated pixels as opposed to raw where you're manipulating, well, raw pixels. (You can make the argument that as red is compressed they are manipulated, but it's *effectively* lossless so whatever). So to answer the question about desaturated images, that's what you want so you can do whatever you want with it in post.

Now if you're talking about what you see in the monitor, if it's desaturated looking it's probably a settings thing. The camera lets you apply a gamma curve and a color space to the image for display so you at least have on set a better idea of what you'll be getting. You can use Redspace, Rec.709, or a pre-defined custom LUT if you like. This way you have a closer notion of what the final image will look like.

As far as over-exposure goes, well it's still a video camera and you have to treat it like one. I've seen people get this wrong a lot. Part of it though is the camera. From what I gather 320 ASA on the camera is really more like 250. I've also seen people set it to 500 because they didn't like what they were getting on the monitor but still don't realize they need to be metering at 320. Actually most people I see with this camera don't meter anyway, they trust the to the histogram which isn't a bad tool, but...

Supposedly, the Red excels on daylight too. Tungsten balance isn't the sweet spot, so that could account for some of the deficiency you see.

But don't take it necessarily from me. I've only assisted with the Red a couple times. Most of what I know is regurgitated from Red Centre. I'd actually be very happy to be corrected by people with more experience.
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#3 Murali Pallikonda

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Posted 14 May 2009 - 05:46 AM

Thanks Chris.

Initially, I used to depend on Light Meter instead of Histogram and was getting highlights blown. Shooting with histogram seemed to be a better way of preserving highlights. Film is more excusing in that regard when you use Light Meter and highlights don't get blown.

I was talking about the image during post (desaturated look), when opened with Red Cine. Once we apply "S" curve, image is better.
My question is why does it look like that ? We call it a raw image, so, shouldn't it match with what our eyes perceive ? What factors are causing to make it look like that ?

I have not seen raw footage by other cameras like D21, so, I'm not sure if this is the characteristic of Red One or raw footage in general.
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#4 Serge Teulon

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Posted 14 May 2009 - 06:11 AM

The red produces a 'flat' image so that it can 'concentrate' in capturing as much information as possible. That is why you see grey, low contrast like images from the red.
As Chris has said, red relies on post manipulation to achieve your final look.

Makes you think twice about he post work that was needed to achieve the visual quality of Knowing!

Edited by Serge Teulon, 14 May 2009 - 06:11 AM.

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#5 Chris Durham

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Posted 15 May 2009 - 03:25 PM

We call it a raw image, so, shouldn't it match with what our eyes perceive ?


Well that's just it. The raw image from a camera isn't the same thing as a "raw" image to the eye or a "raw" image on celluloid. A sensor collects light in a linear fashion. Light hits a photosite and that photosite measures it and outputs a value. The human eye, like film, is more or less sensitive to various intensities of light. This is why a logarithmic space is also sometimes called perceptual. So a truly raw image off a sensor is going to appear flat to our perception.

Don't be confused by RAW on your still camera either. I have a Canon camera that I shoot stills with and I bring it into Adobe Camera Raw and it already has the AdobeRGB color space applied. The camera has preserved the raw data, but applied a default curve and gamut to it, much the same way you can use RedSpace to view a more "real life" sample of the Red output on your monitor. But a truly Raw file is going to be neutral.

I have not seen raw footage by other cameras like D21, so, I'm not sure if this is the characteristic of Red One or raw footage in general.


I don't know about the D21, but take a look at the Genesis. It doesn't have a Raw output. By default it applies a Panalog curve to the output. There are other things you can do with LUTs and whatnot, but, much like any non-raw video camera the output is pretty much gamma-encoded for you.

Another camera to look at is the upcoming Ikonoskop A-Cam dII. The few samples that have come out are very flat looking, but this camera is outputting a true raw file (Adobe DNG sequence). The expectation is that you will manipulate it in post. To put this in film terms, you are basically designing your own stock because you get to define the characteristic curve on a shot by shot basis.
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#6 John Sprung

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Posted 15 May 2009 - 05:07 PM

Now if you're talking about what you see in the monitor, if it's desaturated looking it's probably a settings thing.

From what I gather 320 ASA on the camera is really more like 250. I've also seen people set it to 500 because they didn't like what they were getting on the monitor but still don't realize they need to be metering at 320.


Raw data contains a wider dynamic range than we can display at its real contrast on a monitor, and narrower than existed in front of the camera in the real world. So, its sort of an angels dancing on pin heads thing to speculate about the raw image having a "look". It has limits, but still we can't really see the whole raw range at once. We have to squish and chop to see it at all. So, the setup of the monitor and the processing you do to get it there is what stands between you and really seeing the "look" of the raw image.

You have to make decisions in post as to what you want it to look like. Before those decisions are made, there needs to be a default way of getting a first look at the image, so you can start working on it. Generally what is done is all squish and no chop. They reduce the contrast to an unnaturally low level to get all the range of the data mapped into what the monitor can display. That's very flat and ugly looking, but you gotta start somewhere. You could use a different default, blowing out some whites and crushing some blacks, or with a different gamma curve. But it doesn't much matter, you're going to change it to get what you want.

ASA on the Red camera is a tricky thing. The sensitivity of the chip never changes. There's no gain, like with a video camera. So, setting it to 500 isn't like loading faster film in a photochemical camera. What it does is kinda the opposite, it's like setting your light meter to 500 while the film is still the same 320. The setting on the camera only controls where the zebra displays kick in.





-- J.S.
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#7 Murali Pallikonda

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Posted 16 May 2009 - 09:11 AM

Thanks much, John, Chris, Serge.
It's clear now.

Murali
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