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Author Topic: Does a raw file have a color space?  (Read 186209 times)

digitaldog

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Does a raw file have a color space?
« Reply #40 on: January 19, 2008, 01:16:25 pm »

Quote
Primaries exist only in an orthogonal system. Raw files do not have primaries.

RAW file - just a data file

So while we could agree its a data file (no arguments there), we still go back to the original writings of Bruce (essentially Grayscale) versus that of others (color data). Which is it?

Even the four color geeks (three true color scientists that do this for a living) seem to either somewhat disagree or use differing language.

Both Eric and Jack are members of the ICC and spend a great deal of time in the various committees (both part of the camera committee) trying to define these kinds of terms. What hope do we have here of coming to some agreement in terms???
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Schewe

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Does a raw file have a color space?
« Reply #41 on: January 19, 2008, 01:35:01 pm »

Quote
Both Eric and Jack are members of the ICC and spend a great deal of time in the various committees (both part of the camera committee) trying to define these kinds of terms. What hope do we have here of coming to some agreement in terms???
[a href=\"index.php?act=findpost&pid=168204\"][{POST_SNAPBACK}][/a]


OK, so screw it. I'm gonna go back to saying a raw file is NOT yet a rendered color file (it's raw color data) and is essentially grayscale image data (with the pixels representing what the color could be) waiting to be interpreted into color as a result of a demosaicing process. I also still think that the raw file doesn't have "A" color space as the term "color space" is commonly used.

So now I've gone full circle and think Bruce was more right that Mr. Bill Janes...who seems hellbent on arguing about how many angels can fit on the head of a pin...my thought? One really fat angel or a bunch of really skinny angels but in the grand scheme, since I don't believe in angels, it's a moot point.
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bjanes

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Does a raw file have a color space?
« Reply #42 on: January 19, 2008, 01:37:05 pm »

Quote
Yes he does. And a good lawyer could continue to use the above words of Thomas to try to sway the jury, for example:
When is this early process step happening (before or after we have a raw)? If after, then the lawyer could say "well until that step, this Raw hasn't filled in the missing values, there's no color (yet)".

Chris further lumps the camera and the Raw color space issue into one:
We agree a camera has a color space/color mixing function but what about the Raw? He's somewhat unclear here.

The lawyer could even argue that what Eric says here doesn't apply to the Raw data:
All heading us back to the "Essentially Grayscale", somewhat ambiguous original statement about the Raw data itself.

In the end, too many semantics!
[a href=\"index.php?act=findpost&pid=168180\"][{POST_SNAPBACK}][/a]

If we need to call in a lawyer, then we are in deep trouble. They know nothing about color theory but are very good at obfuscating and will advance any thesis that the client wants, as long as they get paid. They do not seek truth, but rather results for their client. After all, do you think OJ is innocent?

Thus far, no one has come up with an ironclad definition of a color space, and indeed there probably are many kinds of color space. What we have had is a good scientific discussion where most agree that the camera has a space with many but not all of the attributes associated with well defined matrix spaces and how camera tri-stimulus values may be rendered imperfectly into a better defined space such as ProPhotoRGB. I think it is time to close down this thread. I agree that semantics will get us nowhere. Everyone can declare victory (should that be necessary) and turn to the next topic.

Bill
« Last Edit: January 19, 2008, 01:40:16 pm by bjanes »
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digitaldog

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Does a raw file have a color space?
« Reply #43 on: January 19, 2008, 01:56:39 pm »

Quote
OK, so screw it. I'm gonna go back to saying a raw file is NOT yet a rendered color file (it's raw color data) and is essentially grayscale image data (with the pixels representing what the color could be) waiting to be interpreted into color as a result of a demosaicing process. I also still think that the raw file doesn't have "A" color space as the term "color space" is commonly used.

I'd agree, its a non rendered image. I think going full circle, we're not too much closer to agreement. "Essentially Grayscale data" doesn't seem to be any more or less inaccurate and that Bruce was careful here using the important caveat of "essentially". None of the four color experts have dismissed this idea (yet) but I hope to hear back from them based on Jack's last post.
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Panopeeper

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Does a raw file have a color space?
« Reply #44 on: January 19, 2008, 02:28:17 pm »

One of the citations above gives away the "secret":

A purist might argue that a color space not based on colorimetry is not really a color space

i.e. it is the question of definition. If your definition requires that a color space be colorimetric, then raw data does not qualify due to ambiguity.

However, this "greyscale" approach is still nonsense, independently of the accepted definition, and honestly, I find its endless repetition quite ridiculous. The question is not if the raw file represents a color image but how the colors can be described.
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Gabor

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Does a raw file have a color space?
« Reply #45 on: January 19, 2008, 02:33:46 pm »

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OK, so screw it. I'm gonna go back to saying a raw file is NOT yet a rendered color file

Since when is "rendered" a requirement for being a color space?

Btw, what is "rendered"? Is a JPEG in Exif format a "rendered" file? What about a Lab file?
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Gabor

Graeme Nattress

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Does a raw file have a color space?
« Reply #46 on: January 19, 2008, 02:47:12 pm »

A so called RAW image is just data. I tend to think of the bayer pattern as a clever form of image compression 3:1, and it only becomes an image again after demosaicing. Displaying the RAW data is perhaps useful for geeks like  me who develop raw conversion software, but not for much else. It's just a visual representation of data, not an image, which to me is a representation of the image you wanted to capture with the camera. Once it's demosaiced to RGB it has a colour space, that being Camera RAW colour space for that particular camera.

Graeme
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digitaldog

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Does a raw file have a color space?
« Reply #47 on: January 19, 2008, 02:55:39 pm »

Quote
If we need to call in a lawyer, then we are in deep trouble. They know nothing about color theory but are very good at obfuscating and will advance any thesis that the client wants, as long as they get paid. They do not seek truth, but rather results for their client. After all, do you think OJ is innocent?

Lets look this over from the beginning. For me, it's Bruce's book that introduced me to the concepts and he states as we've heard over and over "Raw is essentially Grayscale data". I've used this sentence too (and that started this entire slew of posts after you decided that's not accurate). OK, I'm fine with that, lets look where we've come so far and see if we've learned anything useful. The word "essentially" may be considered a cop-out, but I suspect Bruce like the other four experts I've asked, understood this well and the term is necessary (he's not saying a Raw document IS Grayscale or that a Raw document is in a color space).

One side wants to call the Raw data essentially Grayscale, the other wants to say its data in a color space. The middle ground seems to say the data has the potential to be color data in a color space. One camp asks "if the Raw data isn't essentially Grayscale and is in a color space, what is it?" The other camp suggests this is defined or can be defined. One group suggests that by their definition of a color space, the colors have to fall within human vision (other wise, we're talking about "Imagery Colors" and colors we can't see are not colors at all). We have the issues of colors that fall outside human vision and possibly captured by the camera (and represented by the Raw?) as not being colors in a color space due not being non-colorimetric; that further muddies the waters. One side says that we need three defined primaries to even consider data in a color space. The 5 experts (four mentioned above, the 5th being Bruce who unfortunately can't comment here), seem to have subtle differences in what they define as a color space and in some cases refer to the camera not the Raw data, the root of this argument.

Are we any closer to agreement? I'm still no the fence. But I'm a Gemini.

It appears that without the spectral properties of the chip and some other necessary data, we can't even define the color space of the capture. Does that mean the Raw data defines a color space? Or a potential color space? What is the color space of an untagged RGB document? If we don't know, can we say that its composed of three Grayscale channels? (I'd say yes) but without that definition of the scale of the numbers, is it essentially Grayscale with a potential to be a color space we can define? Can we even say a set of values that represent multiple Grayscale values is a color space if we don't know the scale of the values?
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digitaldog

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Does a raw file have a color space?
« Reply #48 on: January 19, 2008, 02:59:26 pm »

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Once it's demosaiced to RGB it has a colour space, that being Camera RAW colour space for that particular camera.
[a href=\"index.php?act=findpost&pid=168225\"][{POST_SNAPBACK}][/a]

No argument there! But what about before? The crux of debate. Is a Raw a color image? Is it in a color space? If I take an image in sRGB in Photoshop and split the color channels into three documents, is that still an sRGB image or do I have to merge the data (and assign a profile)? If a tree falls in the forest and no one is around.... Never mind.

Going back to square one, is calling a Raw "essentially a Grayscale file" any more or less accurate to saying its "essentially a color image"?
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digitaldog

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Does a raw file have a color space?
« Reply #49 on: January 19, 2008, 03:05:51 pm »

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Thus far, no one has come up with an ironclad definition of a color space, and indeed there probably are many kinds of color space.


Here's mine:

Quote
Color model: A method of mapping color using a set of defined dimen-
sions. Some scientific color models such as x,y,Y or L*a*b* encompass all
of human vision and have a defined scale such that a particular color will
always have the same set of values. Other color models such as RGB or
CMYK have no standard defined reference or scale. In order to under-
stand a color in these models you must have a color space definition that
provides a scale and reference.

Color space: A color space is a scientifically defined portion of human
vision. A color space may be defined with any color model. The RGB
values R10,G100,B10 have no meaning by themselves other than the
color is mostly some kind of green. By using a color space definition, the
same set of values can be translated into one of the scientific color models,
giving the values exact meaning. Having a set of RGB values associated
with a color space allows for the exact reproduction of the color.

A color space is a color model that has a known reference and scale, in this case primaries (the
ingredients) and scale (specific quantities of these ingredients).
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bjanes

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Does a raw file have a color space?
« Reply #50 on: January 19, 2008, 03:53:33 pm »

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Here's mine:
[a href=\"index.php?act=findpost&pid=168228\"][{POST_SNAPBACK}][/a]

"Color space: A color space is a scientifically defined portion of human
vision. A color space may be defined with any color model. The RGB
values R10,G100,B10 have no meaning by themselves other than the
color is mostly some kind of green. By using a color space definition, the
same set of values can be translated into one of the scientific color models,
giving the values exact meaning. Having a set of RGB values associated
with a color space allows for the exact reproduction of the color. "

The above quote was without attribution, so I don't know whose definition that is nor do I know if it is accepted by the scientific community.  However, if one does use that definition, then a raw file or a digital camera does not have a color space, since as Thomas Knoll has stated on 1/18/08 9:36 AM,:

"The fact that a mosaic array is “grayscale” is a red herring in this argument.  An early processing step fills in the missing values, and you have a 3 or 4 channel image as a result.  For most cameras, if you just “assign” a working space RGB profile, you get a recognizable color image as a result, so it certainly seems like a color space.

The camera color space differences from a more common working color space in that it does not have a unique one-to-one transform to and from CIE XYZ space.  This is because the camera has different color filters than the human eye, and thus sees colors differently.  Any translation from camera color space to CIE XYZ space is an approximation because of this."

Since the model is an approximation rather than exact it would not fulfill the definition. If you and Jeff want to go through these contortions so as save face, that's OK with me. Since I am not a color expert, I would accept the analysis put forth by Thomas Knoll, Chris Murphy, and Eric Walowit.
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bjanes

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Does a raw file have a color space?
« Reply #51 on: January 19, 2008, 04:05:49 pm »

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OK, so screw it. I'm gonna go back to saying a raw file is NOT yet a rendered color file (it's raw color data) and is essentially grayscale image data (with the pixels representing what the color could be) waiting to be interpreted into color as a result of a demosaicing process. I also still think that the raw file doesn't have "A" color space as the term "color space" is commonly used.

So now I've gone full circle and think Bruce was more right that Mr. Bill Janes...who seems hellbent on arguing about how many angels can fit on the head of a pin...my thought? One really fat angel or a bunch of really skinny angels but in the grand scheme, since I don't believe in angels, it's a moot point.
[a href=\"index.php?act=findpost&pid=168208\"][{POST_SNAPBACK}][/a]

And I would propose that Thomas Knoll and Chris Murphy are more right than Mr. Jeff Schewe. He accuses me of arguing about how many angels fit on a pin, but what he seems to be trying to accomplish is having to retract any of his ill-considered statements and reach any common understanding of the scientific principles involved. His broken record method of debate reminds me of that used by Joseph Goebbels. As I have stated, I think the matter should be laid to rest, but Jeff just can't do that and is again attempting to malign my search for truth.
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Schewe

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Does a raw file have a color space?
« Reply #52 on: January 19, 2008, 05:25:57 pm »

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As I have stated, I think the matter should be laid to rest, but Jeff just can't do that and is again attempting to malign my search for truth.
[a href=\"index.php?act=findpost&pid=168233\"][{POST_SNAPBACK}][/a]

So, YOU start a thread...we wander all over the topic, we get the feedback and input from people who CLEARLY have more knowledge than all the posters in this thread combined, we (meaning Andrew and I) make an attempt at addressing the issue, definitions and what could be called misconceptions and you are whining that YOUR "search for the truth" is being "maligned" by me?

You gotta be kidding me...right?

Jeeesh...
« Last Edit: January 19, 2008, 05:26:27 pm by Schewe »
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John Sheehy

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Does a raw file have a color space?
« Reply #53 on: January 19, 2008, 05:27:47 pm »

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No argument there! But what about before? The crux of debate. Is a Raw a color image?
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Schewe

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Does a raw file have a color space?
« Reply #54 on: January 19, 2008, 05:31:12 pm »

Uh huh. . .maybe Andrew should have said Is a Raw file a USABLE color file without demosaicing?
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Graeme Nattress

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Does a raw file have a color space?
« Reply #55 on: January 19, 2008, 05:36:25 pm »

RAW data is just data. You can represent it in a number of ways, you can visualize that data in a number of ways. One way is a string of numbers. Do numbers have colour? No! Can they represent colour? Absolutely yes!

If you think RAW does not have a colour space because you visualize raw as a greyscale image, then surely that is because of the visualization, not because of the data, which when correctly interpreted does indeed have a colour space because it's an RGB image.

We must separate data from it's many possible visualizations. To ask a question about colour  when you have a monochrome visualization in your head is to ask a meaningless question. To ask if RAW has a colour space, to me, means  you're visualizing what the RAW data represents, which is an RGB image, and then the question is no longer meaningless.

Graeme
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DarkPenguin

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Does a raw file have a color space?
« Reply #56 on: January 19, 2008, 06:12:18 pm »

Fight!  Fight!  Fight!

Seriously, tho, do I need to know any of this?  I mean does it help me process my images somehow?
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Josh-H

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Does a raw file have a color space?
« Reply #57 on: January 19, 2008, 08:19:49 pm »

You guys all make my head spin...

Just when I think I am getting a decent understanding of color science I read a thread like this.....

i think the last point above is a good one though..

does any of this really make a difference to how we process our images?????

Seems to me its mostly accademic - anyway as long as the debate is healthy its all good.
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digitaldog

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Does a raw file have a color space?
« Reply #58 on: January 19, 2008, 09:20:24 pm »

Quote
Fight!  Fight!  Fight!

Seriously, tho, do I need to know any of this?  I mean does it help me process my images somehow?
[a href=\"index.php?act=findpost&pid=168259\"][{POST_SNAPBACK}][/a]

No. But for some, its interesting and useful to know what's happening under the hood.

Jack Holms just sent this and for those following the debate with interest, its useful to digest:
Quote
A raw image does have a color space if we allow non-colorimetric values to be called color space values. If we don’t allow this then only colorimetric cameras (of which there are very few) have color spaces.

I think it is easer to allow non-colorimetric color spaces and use “colorimetric color spaces” than to invent a new term for non-colorimetric color spaces. (Actually, about ten years ago I proposed the term “spectral space” in ISO but no one liked it.)

What I think is misleading is to give the impression that non-colorimetric cameras have a well-defined relation to colorimetry. Yes, we can estimate colorimetry well enough for practical purposes but different estimates can produce different results and be equally valid.

It is important that critical photographers understand this otherwise they might wonder why they get different results photographing the same scene with different cameras, even when they use the same raw converter. Or, why different conversions to scene-referred produce different results for the same scene and camera. You need to know there is judgment involved in designing the conversion otherwise you won’t know to perform evaluations to see what conversion you like best.
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Tim Lookingbill

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Does a raw file have a color space?
« Reply #59 on: January 19, 2008, 10:47:55 pm »

Been following along here. Interesting concepts being discussed.

The bayer pattern bird pick got me to thinking what that color space would be to get it to look correct which the bird seems to be already rendered correctly, but by RGB colorants as seen through my vLUT and Monitor colorants. I guess the color space of that image is now in is close to sRGB P22 colorants.

What are the colorants of the actual Bayer filter pattern used to filter the photons coming in to come up with the RGB filtered grayscale densities for each camera?

I've been reading the Help section of Raw Developer which has a custom matrix based profile builder you can build a profile visually by attempting to get the Raw image to render a scene as intended. It was too difficult. Better results using RD's L*a*b* curve tool.

Anyway, this is the quote from the RD Help section about editing and/or creating custom profiles in camera native space:

..."In general digital camera sensors are "linear" and record values proportional to the intensity of light striking the sensor. Most digital cameras also use a form of color filter array (known as a Bayer filter) which filters light into RGB components (red, green, blue) though the precise definition of what color "red" or "green" or "blue" may be is not specified. Some cameras use CMY (cyan, magenta, yellow) filters or other color filter arrangements or even other methods of color capture entirely."...

Are there other RGB colorant forumlas out there other than P22 phosphors and if so how do we find them? Wouldn't this help define the camera/Raw color space?
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