Luminous Landscape Forum
Raw & Post Processing, Printing => Digital Image Processing => Topic started by: bobrobert on November 20, 2007, 10:31:42 am
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If someone was to change the colour space of their image from AdobeRGB 98 to pro photo would the colour noise be more apparent and would this necessitate a stronger noise reduction in the chroma settings In a nut shell does a wider colour space mean a more noise in an image?TIA
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If someone was to change the colour space of their image from AdobeRGB 98 to pro photo would the colour noise be more apparent and would this necessitate a stronger noise reduction in the chroma settings In a nut shell does a wider colour space mean a more noise in an image?TIA
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I will try and explain it better My work flow up until now was to select Adobe RGB 98 in camera raw prior to processing After reading the benefits of using the pro photo setting in camera raw yesterday I noticed that a 1600 iso image looked more noisy than when it was set to Adobe RGB 98 Was I imagining this? IF not then when using neat image I would have to reduce noise more? Thus degrading the image more? Does a wider colour space mean more noise reduction? Or have I got it all wrong?TIA
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I will try and explain it better My work flow up until now was to select Adobe RGB 98 in camera raw prior to processing After reading the benefits of using the pro photo setting in camera raw yesterday I noticed that a 1600 iso image looked more noisy than when it was set to Adobe RGB 98 Was I imagining this? IF not then when using neat image I would have to reduce noise more? Thus degrading the image more? Does a wider colour space mean more noise reduction? Or have I got it all wrong?TIA
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Are you shooting Raw?
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Are you shooting Raw?
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Yes Basically I am wondering about noise reduction in different colour spaces If a colour space has a bigger gamut does it need greater noise reductionTIA
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Yes Basically I am wondering about noise reduction in different colour spaces If a colour space has a bigger gamut does it need greater noise reductionTIA
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Raw has no color space. You encode a rendering into a color space and hopefully, you can control as much noise reduction in the Raw rendering state as possible prior to encoding.
You DO want higher bit depth in wider gamut spaces, that's for sure.
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If someone was to change the colour space of their image from AdobeRGB 98 to pro photo would the colour noise be more apparent and would this necessitate a stronger noise reduction in the chroma settings In a nut shell does a wider colour space mean a more noise in an image?TIA
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No. Unless you do something silly like assigning ProPhoto to a sRGB JPEG. But that will cause major saturation overkill.
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Raw has no color space. You encode a rendering into a color space and hopefully, you can control as much noise reduction in the Raw rendering state as possible prior to encoding.
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That statement is debatable. Look at the Adobe [a href=\"http://www.adobe.com/products/dng/pdfs/dng_spec.pdf]DNG Specifiation[/url] on page 47 where mapping from the camera color space to the CIE XYZ space is discussed. The conversion is done with a three by three matrix, just like a conversion from sRGB to ProPhotoRGB is done. If you look at the source code of DCRaw you can review the actual matrix coefficients and conversion code.
Apparently the folks at Adobe think that the camera has a color space.
Bill
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Apparently the folks at Adobe think that the camera has a color space.
Bill
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Isn't this all about semantics?
The raw data as such don't have a color space in the sense that they have a meaning in terms of PCS, they're just values.
The matrix you describe acts as an input profile to map linearized camera values to PCS.
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Isn't this all about semantics?
The raw data as such don't have a color space in the sense that they have a meaning in terms of PCS, they're just values.
The matrix you describe acts as an input profile to map linearized camera values to PCS.
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If the raw data were to have no meaning with respect to the PCS, then obviously it would not be possible to convert them to the PCS. Since they do have a relationship to the PCS, it is possible to convert from the camera space to CIE XYZ by a standard three by three matrix conversion. Here is an excerpt from the source code of DCRAW:
/*
Thanks to Adobe for providing these excellent CAM -> XYZ matrices!
*/
void CLASS adobe_coeff (char *make, char *model)
static const struct {
const char *prefix;
short black, trans[12];
{ "NIKON D200", 0,
{ 8367,-2248,-763,-8758,16447,2422,-1527,1550,8053 } },
As you can see, these values are a 3 by 3 matrix to convert from the Nikon D200 colorspace to CIE XYZ. Once that is accomplished, another transformation to the working space (e.g. Adobe RGB) can be performed. The details are described by [a href=\"http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC18]Poynton[/url]. What is the difference?
As Bruce Fraser explained in Real World Photoshop CS2, a custom RGB space contains there elements: Gamma, White Point, and Primaries.
In the raw file some of these are implicit. The gamma is one, the white point is described by the white balance data in the raw file, and the primaries are described in the matrix. What is missing?
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In the raw file some of these are implicit. The gamma is one, the white point is described by the white balance data in the raw file, and the primaries are described in the matrix. What is missing?
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The spectral sensitivity of the chip.
Bruce's book points out that these chips are simply counting photons. There are colored filters over the matrix (we don't know anything about those colored filters). It is this reason I said the Raw file is Grayscale but I should probably have said something like the Raw file is essentially Grayscale.
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The spectral sensitivity of the chip.
Bruce's book points out that these chips are simply counting photons. There are colored filters over the matrix (we don't know anything about those colored filters). It is this reason I said the Raw file is Grayscale but I should probably have said something like the Raw file is essentially Grayscale.
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Those matrix coefficients describe the spectral characteristics of the chip; again, without this information, it would not be possible to decode the raw file.
You state that a raw file is grayscale, but by the same token, as Bruce states on p. 119 of Real World PSCS2, "In Photoshop, files saved in the RGB mode typically uses a set of three 8 bit grayscale files..." [bold added for emphasis]. No essential difference here.
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Those matrix coefficients describe the spectral characteristics of the chip; again, without this information, it would not be possible to decode the raw file.
You state that a raw file is grayscale, but by the same token, as Bruce states on p. 119 of Real World PSCS2, "In Photoshop, files saved in the RGB mode typically uses a set of three 8 bit grayscale files..." [bold added for emphasis]. No essential difference here.
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Let's quote Bruce on a more recent book (and then we have the Schewe update which I haven't seen yet):
Page 2 of RW camera Raw:
A Raw file is a record of the sensor data, so lets look at what the sensor in a digital camera actually captures. A number of different technologies get lumped into the category of "digital camera." but virtually all the cameras supported by the Camera Raw plug-in are of a type known as "mosaic sensor" or "color filter array" cameras (virtually all because versions 2.2 and later support the Sigma camera based on the Foveon's X3 technology). The first point is that stripped-array Raw files are grayscale!
Color filter array cameras use a two dimensional area array to collect the photons that are recorded in the image. The array is made up of rows and columns of photosensitive detectors-typically CCD or COMS, to form the image.
Further on page 3 he writes:
But the sensors in the array, whether CCD or CMOS just count photons-they produce a charge proportional to the amount of light they receive-without recording any color information.[/u] The color information is produced by color filters that are applied over the individual elements in the array in a process known as "striping"-hence the term "striped array".
Getting back to your quote of Bruce's, its apples and oranges here. He's talking about an RGB file which of course is three Grayscale channels. That's not what he (or I) are talking about with respect to Raw. AFTER demoiscing, when the data is rendered it is in some RGB color space (in Camera Raw and LR, that's ProPhoto RGB linear encoded gamma) and then you can pick an output color space (an encoding color space). But long before this, your Raw data is Grayscale.
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Let's quote Bruce on a more recent book (and then we have the Schewe update which I haven't seen yet):
Page 2 of RW camera Raw:
Further on page 3 he writes:
Getting back to your quote of Bruce's, its apples and oranges here. He's talking about an RGB file which of course is three Grayscale channels. That's not what he (or I) are talking about with respect to Raw. AFTER demoiscing, when the data is rendered it is in some RGB color space (in Camera Raw and LR, that's ProPhoto RGB linear encoded gamma) and then you can pick an output color space (an encoding color space). But long before this, your Raw data is Grayscale.
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I would say that it is more like oranges and tangerines. Both raw and RGB are monochrome, but carry encoded color information. The typical Bayer CFA raw file has four components: green 1 , green 2, blue and red. An RGB file contains three components. What is the difference? You don't need to demosaic to view color information. If you decoded the four streams and viewed the result from a distance, the eye would blend the primaries into the proper colors.
So in essence, Bruce has stated in one publication that RGB consists of 3 monochrome components, and in another that raw has 4 monochrome components. I don't think that the principles of color theory have changed in the more current publication. Furthermore, what is your response to the Adobe DNG specification which refers to a camera color space? This may all be semantics, but the spaces are more similar than they are different. Three by three matrix transformations can be used on either.
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So in essence, Bruce has stated in one publication that RGB consists of 3 monochrome components, and in another that raw has 4 monochrome components. I don't think that the principles of color theory have changed in the more current publication.
So what's the color space of the raw data?
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So what's the color space of the raw data?
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It is the native color space of the camera--in the quoted DCRaw case, that specified by the matrix values shown. In DCRaw, those are used to convert from camera to CIE XYZ. You can then use another 3 by 3 matrix conversion to your working space. Adobe DNG also describes a camera color space. How can you reasonably deny these facts? Did you look at the DNG specification?
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It is the native color space of the camera
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While it may be spec as a 3x3 matrix, what the "camera color space is" is actually the identification of the camera's spectral properties at a given white point...and as such is NOT a "profile" in ICC parlance...so while a camera DOES have a spectral response (at a given white point) is doesn't have a "color space" as it relates to a working space and it's also not an input profile...so saying that a camera does not have a color space profile attached to it would be correct.
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While it may be spec as a 3x3 matrix, what the "camera color space is" is actually the identification of the camera's spectral properties at a given white point...and as such is NOT a "profile" in ICC parlance...so while a camera DOES have a spectral response (at a given white point) is doesn't have a "color space" as it relates to a working space and it's also not an input profile...so saying that a camera does not have a color space profile attached to it would be correct.
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ICC or not, then why does Adobe refer to the Camera Color Space in the DNG specification? Someone at Adobe must consider it to be a color space. As mentioned above, it does have the three main elements of an ICC matrix color space (primaries, TRC, and white point), and it can be transformed to an ICC working space via a 3 by 3 matrix transform. If it looks like a duck, walks like a duck, and quacks like a duck, it may be duck or at least something pretty close. A document in aRGB may not have a color space tag attached to it, but one can be assigned.
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ICC or not, then why does Adobe refer to the Camera Color Space in the DNG specification? Someone at Adobe must consider it to be a color space. As mentioned above, it does have the three main elements of an ICC matrix color space (primaries, TRC, and white point),
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It doesn't have a white point designation until AFTER conversion from the camera color (which is a more accurate way of describing what the raw file contains) to a "color space". All the camera color has is the chromaticities of the spectral response and the assumption of linear gamma. Without the designated white point (to be determined by the metadata tag or overridden by the processing software) it's not yet a complete "color space". Reading the spec is useful, but the terminology must be understood for what it means. This is the same limitation raw captures have when trying to apply input profiles (ala Capture One) to raw captures...since a raw capture doesn't yet have a complete set of chromaticities, gamma and white point, you can't really presume it has a profilable color color space.
And, returning to the OP question;
In a nut shell does a wider colour space mean a more noise in an image?
No...the noise in an image is dictated by the ISO settings in combination with the expansion of darker tones to lighter tone (lightening the shadows) such as would occur when moving the Exposure setting (or Brightness) to the plus values...
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It doesn't have a white point designation until AFTER conversion from the camera color (which is a more accurate way of describing what the raw file contains) to a "color space".
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It does have white balance information, which DNG encodes as AsShotNeutral and as AsShotXY. Doesn't that count as white point designation?
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It does have white balance information, which DNG encodes as AsShotNeutral and as AsShotXY. Doesn't that count as white point designation?
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You keep fishing for a raw file or DNG to have a "color space" as it is commonly associated with ICC style profiles and Photoshop working spaces. If you want to parse the words of the DNG spec and presume to attribute terms and their meanings, more power to ya, but it does a disservice to the industry to engage in a practice that will end up confusing people's understanding of raw linear captures and Photoshop working spaces and input profiles associated with scanners and cameras...
Raw captures do NOT have a "color space as it is defined by the ICC spec and associated with working color spaces in Photoshop". Raw captures are actually grayscale files whose color attributes are not yet assigned until the demosiacing process.
There, ya happy?
Ya know, sometimes you end up beating a dead horse bud...and the horse is beyond caring.
(and other people's eyes start to glaze over)
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If someone was to change the colour space of their image from AdobeRGB 98 to pro photo would the colour noise be more apparent and would this necessitate a stronger noise reduction in the chroma settings In a nut shell does a wider colour space mean a more noise in an image?TIA
The consequences of using Pro Photo in the ACR conversion are:
1. some colors, which are not contained in aRGB nor in sRGB are now representable, particularly in the deep blue and red,
2. the resulting gamut is much, much larger than what your monitor can reproduce (already aRGB is larger).
This means, that you don't see everything as it is in the image, consequently what you see is not only the noise in the image, but the noise due to the lack of gamut coverage of the monitor. If this is something perceivable, depends on the actual image.
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You keep fishing for a raw file or DNG to have a "color space" as it is commonly associated with ICC style profiles and Photoshop working spaces. If you want to parse the words of the DNG spec and presume to attribute terms and their meanings, more power to ya, but it does a disservice to the industry to engage in a practice that will end up confusing people's understanding of raw linear captures and Photoshop working spaces and input profiles associated with scanners and cameras...
Raw captures do NOT have a "color space as it is defined by the ICC spec and associated with working color spaces in Photoshop". Raw captures are actually grayscale files whose color attributes are not yet assigned until the demosiacing process.
There, ya happy?
Ya know, sometimes you end up beating a dead horse bud...and the horse is beyond caring.
(and other people's eyes start to glaze over)
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This thread reminds me the [a href=\"http://www.adobeforums.com/webx?14@@.3bc0d8df/0]thread[/url] on the Adobe Camera Raw forum that was set to read only by the forum administrator because of abusive ad hominem attacks on the participants. Schewe's characteristic shouting and bullying is not unlike the tone of that thread.
First of all, no one stated that the native camera space corresponded to an ICC profile, so arguments along that line of reasoning are invalid. Then the argument is that raw files are grayscale and couldn't have a color profile. As Bruce Fraser stated, on p. 119 of Real World PSCS2, "In Photoshop, files saved in the RGB mode typically uses a set of three 8 bit grayscale files..." [bold added for emphasis]. Well, that argument is out.
Then it was stated that the camera data were not a space since there was no white point. Well, CIE XYZ has no white point either, but it is a color space even though it does not meet the ICC spec.
Chapter 6 of the Adobe DNG specification concerns converting from the Camera Color Space to the CIE XYZ Space. Adobe is pretty stupid to spend an entire chapter on something that does not exist. But then the mafia people know better, and they circle the wagons when challenged. If Schewe can't win his argument by reasoning, he resorts to bullying and shouting.
I'm sure that by this point no one is interested in pursuing this topic any further, but I just wanted to make a point. Furthermore, understanding of the camera color space helps us to understand the calibration procedure in ACR. We are modifying the 3 by 3 matrix values from the Adobe Camera Raw defaults to ones more descriptive of our own camera. These coefficients are used to convert the native camera color space to the internal color space of Camera Raw, and represent the Camera Raw Profile.
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Any chance of someone answering my original question? In camera raw does setting Prophoto instead of AdobeRGB increase noise because there is a wider colour gamutTIA
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Any chance of someone answering my original question? In camera raw does setting Prophoto instead of AdobeRGB increase noise because there is a wider colour gamutTIA
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And, returning to the OP question;
No...the noise in an image is dictated by the ISO settings in combination with the expansion of darker tones to lighter tone (lightening the shadows) such as would occur when moving the Exposure setting (or Brightness) to the plus values...
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Bob, your question has been answered.
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Any chance of someone answering my original question? In camera raw does setting Prophoto instead of AdobeRGB increase noise because there is a wider colour gamutTIA
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No. It doesn't.
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Any chance of someone answering my original question? In camera raw does setting Prophoto instead of AdobeRGB increase noise because there is a wider colour gamutTIA
I answered your question as well in post #6 of this thread. Color space has no effect at all on visible noise levels, unless you do something retarded like manually assigning the wrong profile after conversion, which will not only affect visible noise levels, but also cause over or undersaturation. Short answer: NO.
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Any chance of someone answering my original question? In camera raw does setting Prophoto instead of AdobeRGB increase noise because there is a wider colour gamutTIA
The gamut of the camera is much larger, than sRGB or even aRGB. Consequently, when mapping, the original pixel values get closer to each other, the originally existing noise diminishes.
The gamut of ProPhoto is perhaps somewhat larger than the camera's gamut, and anyway much larger than aRGB, so the mapping yields larger spacing between the original pixel values than with aRGB, i.e. more noise.
However, all this is present only in 16-bit TIFF. What you see is far from that; the more colors of the larger gamut "are not there", for the monitor supports only 8bit sRGB, and you probably see noise, which is not in the image; that's what I tried to explain above.
In order to see the "true noise", you have to inspect the raw image in the camera's color space, i.e. w/o converting the colors (but then the colors are not "true", for you are viewing them on an sRGB monitor).
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The gamut of the camera is much larger, than sRGB or even aRGB. Consequently, when mapping, the original pixel values get closer to each other, the originally existing noise diminishes.
The gamut of ProPhoto is perhaps somewhat larger than the camera's gamut, and anyway much larger than aRGB, so the mapping yields larger spacing between the original pixel values than with aRGB, i.e. more noise.
However, all this is present only in 16-bit TIFF. What you see is far from that; the more colors of the larger gamut "are not there", for the monitor supports only 8bit sRGB, and you probably see noise, which is not in the image; that's what I tried to explain above.
In order to see the "true noise", you have to inspect the raw image in the camera's color space, i.e. w/o converting the colors (but then the colors are not "true", for you are viewing them on an sRGB monitor).
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In order to test the noise hypothesis, I rendered the same raw file into sRGB and ProPhotoRGB and analyzed the noise response with Imatest Stepchart. The overall luminance noise is the same (0.38% and 0.36% respectively), but the resulting TRCs are different and the distribution of the noise is different along the TRC. I think that this has to do with the gamma of the spaces (sRGB is 2.2 and ProPhotoRGB is 1.8). The actual gamma of the converted files are 1/1.58 for the ProPhoto and 1/1.68 for the sRGB. If one converts the ProPhotoRGB file to sRGB and reanalyzes, then the noise characteristics are exactly the same.
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The gamut of the camera is much larger, than sRGB or even aRGB. Consequently, when mapping, the original pixel values get closer to each other, the originally existing noise diminishes.
Digital cameras don't have a color gamut, they have color mixing functions.
To even profile a camera, to get some idea of its so called gamut, you have to place a target of known color values in front of the sensor. That target does have a gamut, the gamut of the resulting profile can't be larger than the target, hence the problems here both profiling the camera and trying to define its so called gamut. Then we can discuss how this so called gamut is affected by the illuminant used to shoot the target as well as the dynamic range of whatever you now place in front of the camera or the role of the Raw converter in rendering the image. So, lets not even begin to try to discuss the gamut of a digital camera (because again, it doesn't have one).
The gamut of ProPhoto is perhaps somewhat larger than the camera's gamut, and anyway much larger than aRGB, so the mapping yields larger spacing between the original pixel values than with aRGB, i.e. more noise.
Again, that's simply speculation and I'll add, the gamut of ProPhoto RGB contains colors that fall outside human vision (although digital cameras can clearly capture stuff outside human vision). But, you're using such differing terms and processes that the two just don't sync up.
In order to see the "true noise", you have to inspect the raw image in the camera's color space, i.e. w/o converting the colors (but then the colors are not "true", for you are viewing them on an sRGB monitor).
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And that camera color space would be what? We're talking Raw data again (essentially Grayscale data to get back another post here that's up to debate).
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The gamut of the camera is much larger, than sRGB or even aRGB. Consequently, when mapping, the original pixel values get closer to each other, the originally existing noise diminishes.
This is completely false, at least in relation to how visible the noise is in the image, whether on screen or in a print. Converting from one color space to another alters how the noise is encoded, but as long as all image colors are in-gamut, converting from one color space will have no effect on how noisy the image looks on-screen or printed, as long as you do so in 16-bit mode so that quantization errors are not an issue. Minor differences in noise measurements of the sRGB file versus ProPhoto or whatever cancel out exactly once you correctly account for the differences in gamut and TRC defined by each color space.
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duplicate post deleted by maker
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Digital cameras don't have a color gamut, they have color mixing functions.
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I was waiting for the mob to employ this tactic: falsis in unum, falsis in omnibus , which is used in legal arguments to discredit a witness. A digital camera does not have a gamut in the sense of a space with well defined boundaries. However, the dictionary definition is "an entire range or series <ran the gamut from praise to contempt>" and a digital camera does have a gamut in this general sense.
Rather than nit pick about peripheral issues (digital camera has no gamut, a raw file has no color space), it would be best to remain on topic and address the main issue rather than try to put down others and show one's own erudition. This is a forum where we are all trying to learn, not a court of law with an adversarial climate. The main thrust of the argument was false, as Jonathan pointed out.
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This thread reminds me the thread (http://www.adobeforums.com/webx?14@@.3bc0d8df/0) on the Adobe Camera Raw forum that was set to read only by the forum administrator because of abusive ad hominem attacks on the participants. Schewe's characteristic shouting and bullying is not unlike the tone of that thread.
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Ironically, I never posted in that thread...so I guess Mr. Janes is trying to paint me with a brush of "similarity"...
"shouting and bullying"? Strikes me that THAT is an ad hominem attack...
Never the less, I thought I would show some images to help make my points. Here's a few images from RWCR CS3 showing some rarely seen real raw images:
(http://schewephoto.com/undemosiaced-raw/01-raw-lin-flower.jpg)
The image above is a real raw image, processed but not demosiaced. It was processed through DNG Verifier to show what the image looks like when written to disk...
(http://schewephoto.com/undemosiaced-raw/02-CR-processed-TC.jpg)
Here's the same image processed through Camera Raw.
So, what color space is the original grayscale raw image in? The actual raw image is indeed grayscale until the image is demosiaced...and not only is it grayscale, it's in linear gamma.
You see the tiny green rectangles? Here are some details from those areas...
(http://schewephoto.com/undemosiaced-raw/03-undemosiaced-lin-flower.jpg)
The image above is taken from the original file processed through DNG Verifier then blown up in Photoshop to 3,200 % zoom. You can actually see the original Bayer array pixels. You'll note that the dark pixels in the area that is actually yellow shows the blue pixel photo sites.
(http://schewephoto.com/undemosiaced-raw/04-demosiaced-flower.jpg)
This is the same area of pixels shown in the detail image above. The grayscale tones have now been interpolated into color information. It is this demosiacing interpolation that gives color information to the grayscale pixels.
So, again, in terms of the RAW file before demosiacing interpolation, what would be the "camera color space"? In actuality, it has no color space until the manner of demosiacing interpolation is determined and the tags regarding white point are provided and factored into the interpolation.
Even then those tags are subject to interpretation...what the original raw does have is a spectral response based on the properties of the Red, Green & Blue separation filters that are used to filter the white light to capture the RGB response properties, but that data is held in B&W until demosiacing.
So, ya still think that the original raw capture has a color space?
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The image above is a real raw image, processed but not demosiaced. It was processed through DNG Verifier to show what the image looks like when written to disk...
Very cool Jeff. Where does one get DNG Verifier? This is a great way to illustrate a Raw processed by not yet demosiaced.
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Rather than nit pick about peripheral issues (digital camera has no gamut, a raw file has no color space), it would be best to remain on topic and address the main issue rather than try to put down others and show one's own erudition.
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No put down intended. The fact is, a digital camera doesn't have a color gamut and a Raw file doesn't have a color space. Some here don't consider this a nit pick.
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Very cool Jeff. Where does one get DNG Verifier? This is a great way to illustrate a Raw processed by not yet demosiaced.
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It's part of the DNG SDK...and intended for geeks (Zalman had to teach me how to run it because you run it via command line).
:~)
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(Zalman had to teach me how to run it because you run it via command line).
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OK, never mind. I'm not about to mess around with command lines! But, a very interesting illustration of the processing none the less.
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Digital cameras don't have a color gamut, they have color mixing functions
The gamut is the amount (range) of reproducible colors. This has nothing to do with the question how it can be profiled.
To even profile a camera, to get some idea of its so called gamut, you have to place a target of known color values in front of the sensor
This is the description of how you would do it. Again, it has no role here.
Btw, the spectral responses of the filters define the gamut of the camera, but manufacturers don't publish this information. (Though one could measure it with suitable equipment.)
that camera color space would be what?
That camera color space would be that camera's specific color space. If you want a name to it, use the camera model, or in some cases the sensor "model" (sometimes the same sensor is used in different cameras).
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The gamut is the amount (range) of reproducible colors. This has nothing to do with the question how it can be profiled.
And you define this gamut, from a Raw file how?
To even profile a camera, to get some idea of its so called gamut, you have to place a target of known color values in front of the sensor
This is the description of how you would do it.
And YOU would profile it how?
In light of Jeff's example above, what gamut does the image have processed but not demosiaced?
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And you define this gamut, from a Raw file how?
I don't know, I am not that business. However, some others are obviously doing that (and the manufacturers, who know the spectral response of the filters, certainly know the gamut of their own equipment).
Micheal Reichmann shows the color space of the Canon 20D in here (http://luminous-landscape.com/tutorials/prophoto-rgb.shtml). He even thanks Bruce Fraser and Jeff Schewe for their feedback and suggestions; the latter must have forgotten it already.
In light of Jeff's example above, what gamut does the image have processed but not demosiaced?
You are mixing up the gamut of the camera and of the scenery/actual image. The subject is the former.
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So, what color space is the original grayscale raw image in? The actual raw image is indeed grayscale until the image is demosiaced
Here is the surprize: pls display an RGB color image in PS and disable two of the three channels. Then pls post here, what you see.
and not only is it grayscale, it's in linear gamma
Totally irrelevant.
So, again, in terms of the RAW file before demosiacing interpolation, what would be the "camera color space"?
The range of colors, which can be reproduced by those sensors.
The fact, that the raw data has to be processed before being displayed has no relevance. Try to display a Lab image on an RGB monitor without conversion, or even an RGB JPEG, which is kept in YCbCr form.
The raw data too can be dislayed in color without de-mosaicing, although the result is not as pleasing as after the de-mosaicing.
See the Channel view of the color checker (http://www.panopeeper.com/Demo/ChannelView_ColorChecker.tif). It is in TIF, so that one can see it magnified without JPEG artifacts. In 600% you can see the individual pixels.
(In this view every monitor pixel represents a green, red or blue filtered pixel of the sensor; the two other RGB channels are zero.)
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I don't know, I am not that business. However, some others are obviously doing that (and the manufacturers, who know the spectral response of the filters, certainly know the gamut of their own equipment).
Micheal Reichmann shows the color space of the Canon 20D in here (http://luminous-landscape.com/tutorials/prophoto-rgb.shtml). He even thanks Bruce Fraser and Jeff Schewe for their feedback and suggestions; the latter must have forgotten it already.
You are mixing up the gamut of the camera and of the scenery/actual image. The subject is the former.
[a href=\"index.php?act=findpost&pid=155631\"][{POST_SNAPBACK}][/a]
You sir are the confused one. The gamut they show is based on ICC profiles built as I described by shooting a target (which has a fixed gamut). That doesn't mean the capture device is being fully defined by this profile because its not, because a digital camera doesn't have a gamut as I've tried to explain to you.
In a nutshell, a color mixing function, also called a color matching function, is a mathematical defined representation of a measured color based on three monochromatic RGB primaries that would duplicate the observed color of a measured wavelength. Until its mapped into a defined RGB space, it can’t have a color gamut.
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Here is the surprize: pls display an RGB color image in PS and disable two of the three channels. Then pls post here, what you see.
[a href=\"index.php?act=findpost&pid=155633\"][{POST_SNAPBACK}][/a]
Ah, but the raw capture is not a 3 channel image file...it's a grayscale (single channel) image file (which was the whole friggin' point of posting what the raw files actually looks like).
Through demosiacing, the pixels that represent the R, G, & B photo sites are used to interpolate the component RGB color files. See, it's a case of turning a grayscale file into a color file that is the whole point of a Bayer array sensor.
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From the FAQ's on Munsell Color Science Laboratory:
Question:
"Digital image sensors (such as those used in digital cameras)use red, green, blue ink-based color filters to generate color. Do they therefore have a color gamut that limits the range of colors that they can detect? (255)"
Answer:
"Let's start with the short answer to your question; there is no such thing as a camera, or scanner, gamut. A gamut is defined as the range of colors that a given imaging device can display. To say that a camera had a gamut would be to imply that you could put a color in front of it that it could not possibly respond to. While it is certainly possible that two colors that are visually distinct might be mapped into the same color signals by a camera, that does not mean that the camera could not detect those colors. It just couldn't discriminate them. For example, a monochrome sensor will map all colors into a grayscale image and encode it as such. Certainly the encoding has a gamut (in this case a lightness range with no chroma information), but did the camera responded to all the colors put before it. It is the encoding that imposed the gamut. In the color world, encoding is based on some explicit or implied display. For example, sRGB is a description of a display and therefore defines a gamut (but only if the sRGB values are limited in range). If a camera encodes an image in sRGB, that doesn't mean that the range of colors the camera detected are only from within the sRGB display gamut, but it means the camera data have been transformed to best use that sRGB encoding. As long as a camera has three or more sensors that span the visual spectrum, then it will respond all the same stimuli as our visual system. Whether the camera can discriminate colors as well as the human visual system will depend on the encoding of the camera signals, quantitization, and the details of the camera responsivities. (To return to the black and white system, that camera encodes all the colors into a gray scale. They could then be displayed as any color within a given display, but many colors from the original scene would be mapped to the same values.)
Since there is no such thing as a gamut for an input device, then there is no way to compute it or calculate a figure of merit. Generally, the accuracy of color capture devices is assessed through the accuracy of the output values for known inputs in terms of color differences. Also, sensors are sometimes evaluate in terms of their ability to mimic human visual responses (and therefore be accurate) using quantities with names like colorimetric quality factor, that measure how close the camera responsivities are to linear transformations of the human color matching functions. Doing an internet search on "colorimetric quality factor" will lead you in the right direction."
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Ah, but the raw capture is not a 3 channel image file...it's a grayscale (single channel) image file
LOL, that's good. Each channel of an RGB file is only a grayscale on its own.
Nothing differentiates the color channels, except their interpretation.
You can copy the content of the red channel of an RGB image over the green channel, and suddenly the image has different colors.
The channels of the raw images are greyscale on their own. Together they constitute a color image. The only real difference between raw and RGB channels is, that the "colors" of the raw channels are overlapping. However, this fact does not make the raw image a colorless one.
You are overstressing the role of de-mosaicing. Although it is essential for the reproduction of the original colors, it is not essential for having a color image.
Following images are another views of the raw data (from the same color checker as above, shot with a Nikon D200): no de-mosaicing occured, but now each color filter array is shown as a single pixel; the three RGB components are directly from the raw channels (the two green have been averaged):
(http://www.panopeeper.com/Demo/CompositeView_ColorChecker_NoWB.jpg)
and the same with white balancing:
(http://www.panopeeper.com/Demo/CompositeView_ColorChecker_WB.jpg)
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Nothing differentiates the color channels, except their interpretation.
Question:>So the raw image is actually a grayscale image. OK. It's one grayscale but
>isn't the Bayer pattern actually interleaved in that grayscale image, as far
>as you know?
Answer: No, there's a CFAPattern metadata tag that defines the Color Filter
Array (which is often a Bayer pattern but is sometimes something else
entirely, possibly using more than three primaries). A blue-filtered
pixel will produce a lower luminosity than a red-filtered one that
received the same photon count, so the effect of the CFA is certainly
imposed on the grayscale pixels, but the pixels themselves are
just grayscale pixels.
Bruce Fraser
Do you get it yet?
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LOL, that's good. Each channel of an RGB file is only a grayscale on its own.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=155664\")
No, you STILL don't get it...a raw capture is only a single channel grayscale file. It is only through the demisaicing interpolation that the color data is extracted from the grayscale file and rendered as color data in a 3 channel file.
Note, the original un-demosiaced files that I posted were actually in a linear gamma, grayscale space that I converted to sRGB for the purpose of posting.
You are overstressing the role of de-mosaicing. Although it is essential for the reproduction of the original colors, it is not essential for having a color image.
No, the raw file _IS_ a single channel grayscale file UNTILL demosiacing...you DON'T have ANY color in the single channel file WITHOUT demosiacing.
In the original, single channel grayscale file in linear gamma, each photo site is represented as a single pixel of either red, green or blue data from that photo site (ya gotta blow it up REAL BIG to see the individual pixels). There are 2x the number of green photo sites as red or blue (hence the Bayer array unless you are talking Foveon chips).
To better understand the demosiac process, see: [a href=\"http://en.wikipedia.org/wiki/Demosaicing]Demosaicing[/url]
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You see the tiny green rectangles? Here are some details from those areas...
So, ya still think that the original raw capture has a color space?
[a href=\"index.php?act=findpost&pid=155589\"][{POST_SNAPBACK}][/a]
I can't believe that your reasoning is so very simplistic. If I take a TIFF and delete the blue and red channels, I don't see any green at all. All I see is monochrome. As Bruce Fraser has stated, an RGB file consists of three monochrome channels, so this is not surprising. But by your simplistic interpretation, there is no green in the image. If I view the file in a hex editor all I see are hex numbers. Gee, you have to view the file with a program that knows how to interpret the data.
BTW, you don't have to jump through hoops with some command line program to view undemosaiced files. You can use the freeware program Iris.
Here is a crop from a shot of a flower:
[attachment=4014:attachment]
A closeup of the ACR conversion is on the left and the raw file as shown by iris. The red, blue, and green information is all there in the Bayer grid. The colors of the array can be viewed without demosaicing with the SPLIT_CFA command. Instead of being present on three layers, they are all in one layer in a grid pattern, but they are still there and separate.
[attachment=4015:attachment]
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The colors of the array can be viewed without demosaicing with the SPLIT_CFA command. Instead of being present on three layers, they are all in one layer in a grid pattern, but they are still there and separate.
[a href=\"index.php?act=findpost&pid=155669\"][{POST_SNAPBACK}][/a]
Do you mean channels?
What application are you talking about with the "SPLIT_CFA command"?
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No, you STILL don't get it...a raw capture is only a single channel grayscale file. It is only through the demisaicing interpolation that the color data is extracted from the grayscale file and rendered as color data in a 3 channel file.
[a href=\"index.php?act=findpost&pid=155668\"][{POST_SNAPBACK}][/a]
Schewe, you are the one who is not getting it. With a Bayer array you can use a program such as Iris (do a google search) to separate the Bayer grid into four files representing red, blue, green1 and green2. No demosiacing is involved. The color information is distributed in the grid, whereas with a regular RBG file the color information is on three separate channels. You can not get color from a single gray scale file.
In your demonstration of the Bayer grid, if you painted in color on the grid according to the color of the filter, you would see a color image. Each pixel would have only one color, but if you viewed the image from a distance the colors would be blended by the eye.
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Do you mean channels?
What application are you talking about with the "SPLIT_CFA command"?
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=155671\")
The application I mentioned was Iris. See the [a href=\"http://www.astrosurf.com/buil/iris/tutorial5/doc17_us.htm]tutorial[/url]
BTW, in your example, you are not viewing the unmodified raw data, which are in the range of 0..4095 for a 12 bit camera chip. The image would be so dark you could hardly see it in Photoshop 16 bit (15+1). In my Iris example, I multiplied the values by 15 to bring them into the 0..32767 range expected by Photoshop.
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No, the raw file _IS_ a single channel grayscale file UNTILL demosiacing...you DON'T have ANY color in the single channel file WITHOUT demosiacing
Jeff, don't you get it? The images I posted just above are from the raw file, NOT DE-MOSAICED, only mapped with the sRaw function.
The mapping has no relevance in this question. Here they are in linear mapping, with and w/o WB.
I repeat it: no de-mosaicing has been involved. The three raw channels have been used directly as R, G and B (again, the two greens averaged in the RGB green).
(http://www.panopeeper.com/Demo/CompositeView_ColorChecker_NoWB_linear.jpg)
(http://www.panopeeper.com/Demo/CompositeView_ColorChecker_WB_linear.jpg)
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You can not get color from a single gray scale file.
[a href=\"index.php?act=findpost&pid=155674\"][{POST_SNAPBACK}][/a]
Uh huh. . .so, like a bumble bee can't fly, Camera Raw can't interpolate the color data from a grayscale Bayer array? I think that was the point of demosiacing, to interpret the grayscale CFA file into RGB color?
The SPLIT_CFA gives you 4 separate files...ok, but that's not too useful unless you want to run processing on the individual files considering the size of the files is reduced by a factor of 2...but the CFA image is still a single channel image after you do a MERGE_CFA command. It's the demosiacing that make the single channel grayscale file into an RGB file...right?
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No put down intended. The fact is, a digital camera doesn't have a color gamut and a Raw file doesn't have a color space. Some here don't consider this a nit pick.
[a href=\"index.php?act=findpost&pid=155591\"][{POST_SNAPBACK}][/a]
You are half right: a digital camera does not have a gamut, but the raw file does have a color space as documented in the DNG specification. Have you read Chapter 6 of that spec, and what is your take on it? However, these issues are not the topic of the discussion. IMHO, you brought them up to impugn the knowledge of the poster and score debating points, rather than contributing to the topic being discussed.
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BTW, in your example, you are not viewing the unmodified raw data, which are in the range of 0..4095 for a 12 bit camera chip. The image would be so dark you could hardly see it in Photoshop 16 bit (15+1). In my Iris example, I multiplied the values by 15 to bring them into the 0..32767 range expected by Photoshop.
[a href=\"index.php?act=findpost&pid=155676\"][{POST_SNAPBACK}][/a]
No, I'll admit that I took the linear grayscale (in a linear gray gamma) and transformed it into sRGB...
Here's the actual linear file...in linear gamma.
(http://schewephoto.com/undemosiaced-raw/True-linear.jpg)
There, that better? Course, ya can't hardly see anything in the linear gamma.
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Jeff, don't you get it? The images I posted just above are from the raw file, NOT DE-MOSAICED, only mapped with the sRaw function.
[a href=\"index.php?act=findpost&pid=155679\"][{POST_SNAPBACK}][/a]
So, you are relying on the mapping function to interpret the color data from the grayscale file...in leu of demosiacing.
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Uh huh. . .so, like a bumble bee can't fly, Camera Raw can't interpolate the color data from a grayscale Bayer array? I think that was the point of demosiacing, to interpret the grayscale CFA file into RGB color?
The SPLIT_CFA gives you 4 separate files...ok, but that's not too useful unless you want to run processing on the individual files considering the size of the files is reduced by a factor of 2...but the CFA image is still a single channel image after you do a MERGE_CFA command. It's the demosiacing that make the single channel grayscale file into an RGB file...right?
[a href=\"index.php?act=findpost&pid=155680\"][{POST_SNAPBACK}][/a]
The point is that the SPLIT_CFA command separates the color information into four files, and it can be viewed much as you would view the color channels (R, G, B ) of a TIFF file. The color information is in the raw file and does not need to be extracted by demosaicing. The files are smaller, since there is no interpolation of the missing two colors in each pixel. You could leave blank spaces in the split files, but that would be unsightly.
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So, you are relying on the mapping function to interpret the color data from the grayscale file...in leu of demosiacing.
That's really funny. Somehow I had the feeling, that you will mix up things, therefor I posted two images with linear mapping.
The mapping occurs within the channel. It is not a substitute for de-mosaicing. In these images the red channel of the RGB is from the red filtered pixels, the blue is... etc.
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In these images the red channel of the RGB is from the red filtered pixels, the blue is... etc.
[a href=\"index.php?act=findpost&pid=155687\"][{POST_SNAPBACK}][/a]
Uh huh. . .and WHAT is interpreting the red colored pixels to display as representing RED? A magic wand? Because, without something being told that this pixel in this coordinate represents red, it would still be a grayscale image file.
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So, you are relying on the mapping function to interpret the color data from the grayscale file...in leu of demosiacing.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=155684\")
I could be mistaken, but I was under the impression that Panopeeper posts on the Adobe Camera Raw forum as G Sch and he has written an interesting program that anyalzes and displays raw image files without any demosaicing. If so, he is not an imaging moron, even though he doesn't use gamut in the sense that it is used in digital cameras
[a href=\"http://www.cryptobola.com/PhotoBola/RawnalyzeGuide.htm]http://www.cryptobola.com/PhotoBola/RawnalyzeGuide.htm[/url]
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From the FAQ's on Munsell Color Science Laboratory:
A gamut is defined as the range of colors that a given imaging device can display
This is his definition, not the definition.
While it is certainly possible that two colors that are visually distinct might be mapped into the same color signals by a camera, that does not mean that the camera could not detect those colors. It just couldn't discriminate them
According to this explanation, the gamut of sRGB is the same as that of ProPhoto: one can input the ProPhoto in the sRGB encoding. Although some colors can not be reproduced any more, that does not matter, right?
Look further for definitions, and you will find, the the reproduction of the colors is important.
Example:
Color gamut is the subset of colors, which can be accurately represented...
Depending on the cameras (sensors), certain colors can not be accurately represented (one can not distingush between the colors; in other words, when you see a certain color from the sensor, you can not tell, what color it was originally). This is the reason, that the gamuts of cameras are different.
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Uh huh...and I've used Rawnalyze to look at a raw file before Zalman told me how to output a raw file from DNG Verify...it doesn't alter the fact that something, somewhere has to be able to determine that a specific pixel in a specific coordinate represents R, G, & B. And it's that interpretation of the Bayer array that then represents the grayscale as color data instead of demosiacing. But the original capture is grayscale...
So, Bill, you like the true linear image better? I actually have created both a linear gamma working space in Photoshop as well as a ProPhoto RGB with a linear gamma so I could work with linear gradients in grayscale and color. But the original posted files WERE originally in linear until I transformed into sRGB for the original posting.
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without any demosaicing. If so, he is not an imaging moron, even though he doesn't use gamut in the sense that it is used in digital cameras
Actually, Rawnalyze works with the camera's color space in the sense, that not only no de-mosaicing takes place, but the mapping from camera colors to CIE XYZ is not carried out either. (Of course, this is not correct, because the raw channels do not represent single colors almost the entire spectrum).
Btw, the wording in the DNG specification (written by Adobe) is:
Mapping [span style=\'font-size:14pt;line-height:100%\']Camera Color Space [/span]to CIE XYZ Space
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In a nutshell, a color mixing function, also called a color matching function, is a mathematical defined representation of a measured color based on three monochromatic RGB primaries that would duplicate the observed color of a measured wavelength. Until its mapped into a defined RGB space, it can’t have a color gamut.
So I sincerely hope that camera manufacturers a.) and Adobe Camera Raw b.) are sharing the same definition for CIE XYZ:
a.) to shape the spectral response of the sensor in a way to represent a linear combination of CIE XYZ matching functions.
b.) to facilitate a somewhat correct interpretation of the camera’s gamut by assignment of a matrix space representing an appropriate subset of same CIE XYZ master.
Peter
--
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So, Bill, you like the true linear image better? I actually have created both a linear gamma working space in Photoshop as well as a ProPhoto RGB with a linear gamma so I could work with linear gradients in grayscale and color. But the original posted files WERE originally in linear until I transformed into sRGB for the original posting.
[a href=\"index.php?act=findpost&pid=155692\"][{POST_SNAPBACK}][/a]
Jeff, you already know most of what I am saying below, but others may be interested in the information.
The linear files do not display well without color management, because a gamma of 2.2 is assumed, at least with Windows. I don't know that much about Macs, but I understand they no longer use a gamma of 1.8. If you assign your custom ProPhotoRGB with a gamma of one to the linear file when you open it in Photoshop it will display with normal tonality, but the colors will be off unless your original has ProPhoto primaries. If you take a file with a bit depth of 12 and dump into a 16 bit linear space, it will still look very dark.
An alternative way of viewing a linear file in a gamma 2.2 or gamma 1.8 space is to apply a curve in Photoshop that undoes the gamma encoding. Shown below is a gamma 2.2 curve
[attachment=4018:attachment]
Here is the flower image at gamma = 1 on the left (in sRGB), with the gamma 2.2 curve applied in the middle, and with a contrast boost via an S-curve on the right. Simply applying a gamma of 2.2 results in a very flat image.
[attachment=4019:attachment]
Most HDR encodings use linear gamma without any tone curve (scene referred) and they display normally in Photoshop. If you want to reproduce a scene exactly, there must be a one to one relationship between the source (the scene) and the reproduction. When you view a gamma encoded file or print it, a reverse gamma function is applied but any compression is not undone, or else the image would clip due to limited dynamic range of the print or screen.
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Uh huh...and I've used Rawnalyze to look at a raw file before Zalman told me how to output a raw file from DNG Verify...it doesn't alter the fact that something, somewhere has to be able to determine that a specific pixel in a specific coordinate represents R, G, & B. And it's that interpretation of the Bayer array that then represents the grayscale as color data instead of demosiacing. But the original capture is grayscale...
[a href=\"index.php?act=findpost&pid=155692\"][{POST_SNAPBACK}][/a]
Exactly! And this has been discussed by the color scientist at Munsell (quote above) when he writes that the camera has no gamut. You can't define the gamut or a color space until you place specific coordinates of RG and B. Bruce said this as well.
This is getting to be a big cluster-fu*% of semantics but I'd far prefer to take the side of the color scientists and Bruce, among just a few who state I believe correctly and for the last time, the Raw data is essentially Grayscale and the capture device has no gamut.
And yet another quote from Phil Green:
Bruce is right, there's no gamut boundary associated with a capture
device. If you took a colour at the saturation limit of visual
perception, it would probably be outside any reproduction media gamut
(display, print whatever) but would still be a stimulus to which a
capture device would respond. You do have dyanamic range and
sensitivity limitations that would mean that a whole bunch of colours
would tend to generate the same response - but it would be a response
nonetheless. You could think of the sensitivity limit of a capture device as being its
'effective' gamut, but it makes more sense to me to keep the gamut
boundary concept for physical media and choosing a working space that
corresponds to the gamut of the input media.
--
Phil Green
Colour Imaging Group
School of Printing and Publishing
And again:
On 4/5/99 10:48 AM, "Richard F. Lyon" wrote:
The discussion of profiling Leaf and other cameras is very interesting,
but doesn't go far enough in clarifying the connections with underlying
color science and photographic science (these are very different things!).
Bruce's and Andrew's comments below are right on, but as I say don't go
far enough. A camera (or a scanner) doesn't "HAVE" an RGB gamut unless
it has computation built in to convert its measurements to an RGB space.
If a camera measures a scene through filters that are 'color matching
functions' (see Hunt, especially the section on Television signal
processing) as it should, then ALL colors can be correctly measured and
represented. But then the numbers are usually matrixed to somebody's
standard RGB space, based on a set of primaries. In this process, some
of the pixels can get negative values of R, G, or B, meaning that those
colors are not inside the triangle bounded by the primaries. It is at
this point that the gamut becomes limited, because nobody's output file
formats allow negative values (not even in 16-bit files, stupidly!), so
they clip them one way or another.
So usually what comes out of a camera or scanner is in an ordinary RGB
space that the engineers picked or defaulted to, and of course you can
profile to figure out what the primaries seem to be, what the gamut
limitations are, etc.
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And here is a demonstration of a color image from raw without any demosaicing. One takes the raw file and splits out the red, blue, green1 and green2 portions of the CFA with the Iris SPLIT_CFA command. This gives four files: red, blue, green1 and green2. The files are in the FIT format, which Photoshop can not read, so they have to be converted to TIFF, which I did with the freeware program ImageJ. The result is three gray scale files. They can then be loaded into Photoshop and merged into an RGB file. I used only one of the green separations. This proves that color can be generated without demosaicing.
[attachment=4021:attachment]
The result is gamma 1
[attachment=4022:attachment]
One can then use the gamma 2.2 curve and a contrast boost to get the final result. The background is ugly, but I used what was available to demonstrate the point.
[attachment=4024:attachment]
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The result is three gray scale files. They can then be loaded into Photoshop and merged into an RGB file.
An RGB file in WHAT color space? How did you decide how to map the scale of the RGB primaries from the Raw data? This is the meat and potatoes here. You've got a pile of numbers. What's the scale and how did YOU or your Raw splitting software decide how to define these primaries? That would give us a color space definition. Read what the color scientists and experts I've quoted have said about this assignment. How do YOU define the gamut by defining the scale of the primaries of what isn't a color file?
And I suspect this goes back to the DNG spec you keep mentioning. Where does it tell us the scale of the primaries so we can define a color space and gamut? As I posted by another author, someone, somewhere makes it up more or less.
At the time of demosicing, the primaries are defined, you have a color image. Richard F. Lyon explains it the best:the numbers are usually matrixed to somebody's standard RGB space, based on a set of primaries. The color scientists at Munsell said it too:In the color world, encoding is based on some explicit or implied display.
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And here is a demonstration of a color image from raw without any demosaicing.
[{POST_SNAPBACK}][/a] (http://index.php?act=findpost&pid=155777\")
No, here is a color image from Raw WITH demosaicing!
[a href=\"http://en.wikipedia.org/wiki/Demosaicing]http://en.wikipedia.org/wiki/Demosaicing[/url]
A demosaicing algorithm is a digital image process used to interpolate a complete image from the partial raw data received from the color-filtered image sensor (via a color filter array or CFA) internal to many digital cameras in form of a matrix of colored pixels. Also known as CFA interpolation or color reconstruction, another common spelling is demosaicking.
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An RGB file in WHAT color space? How did you decide how to map the scale of the RGB primaries from the Raw data? This is the meat and potatoes here. You've got a pile of numbers. What's the scale and how did YOU or your Raw splitting software decide how to define these primaries? That would give us a color space definition. Read what the color scientists and experts I've quoted have said about this assignment. How do YOU define the gamut by defining the scale of the primaries of what isn't a color file?
And I suspect this goes back to the DNG spec you keep mentioning. Where does it tell us the scale of the primaries so we can define a color space and gamut? As I posted by another author, someone, somewhere makes it up more or less.
At the time of demosicing, the primaries are defined, you have a color image. Richard F. Lyon explains it the best:the numbers are usually matrixed to somebody's standard RGB space, based on a set of primaries. The color scientists at Munsell said it too:In the color world, encoding is based on some explicit or implied display.
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This is only a proof of concept demonstration with unmanaged colors. Your comments are irrelevant to the demonstration, but the colors could be scaled by performing a 3 by 3 matrix conversion from the camera space to CIE XYZ and then another transformation to one's preferred working space.
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This is only a proof of concept demonstration with unmanaged colors. Your comments are irrelevant to the demonstration, but the colors could be scaled by performing a 3 by 3 matrix conversion from the camera space to CIE XYZ and then another transformation to one's preferred working space.
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NO, my points are very relevant to the original post you made far too many posts ago:
QUOTE(digitaldog @ Nov 22 2007, 08:23 AM)
Raw has no color space. You encode a rendering into a color space and hopefully, you can control as much noise reduction in the Raw rendering state as possible prior to encoding.
-----you said----
That statement is debatable. Look at the Adobe DNG Specifiation on page 47 where mapping from the camera color space to the CIE XYZ space is discussed. The conversion is done with a three by three matrix, just like a conversion from sRGB to ProPhotoRGB is done. If you look at the source code of DCRaw you can review the actual matrix coefficients and conversion code.
Apparently the folks at Adobe think that the camera has a color space.
You say the statement is debatable. We have a debate, one in which you haven't, as yet proven to me (and perhaps anyone else) that a Raw file has a color space. I say its essentially Grayscale, it has no color space. I stick to that opinion. You've quoted page 47 where it states "from camera color space" assuming that this is defined, I've mentioned several well qualified experts who say, its whatever you want to assign the scale of the primaries at encoding which I'll add is happening AT the state of demosaicing. You attempted to demonstrate this above, and so I again ask, what's the color space you made up? And how does this make it 'correct' and further prove that prior to this part of the process, the camera had a gamut?
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Exactly! And this has been discussed by the color scientist at Munsell (quote above) when he writes that the camera has no gamut. You can't define the gamut or a color space until you place specific coordinates of RG and B. Bruce said this as well.
This is getting to be a big cluster-fu*% of semantics but I'd far prefer to take the side of the color scientists and Bruce, among just a few who state I believe correctly and for the last time, the Raw data is essentially Grayscale and the capture device has no gamut.
And yet another quote from Phil Green:
And again:
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Digidog, you are confusing the issue. I did not state that a digital camera has a gamut. A raw file is gray scale according to your nomenclature, and Bruce stated p. 119 of Real World PSCS2, "In Photoshop, files saved in the RGB mode typically uses a set of three 8 bit grayscale files..." [bold added for emphasis]. The grayscale files can form a color image because the three primary colors of the image are represented by the grayscale files. The raw file is also gray scale, but a color image can be formed from the red, blue and green elements of the Bayer array. In the latter case, all three primaries are encoded into one file rather than three separate files. If you can't see the analogy, I don't think you are very bright.
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Digidog, you are confusing the issue. I did not state that a digital camera has a gamut.
Fine
A raw file is gray scale according to your nomenclature, and Bruce stated p. 119 of Real World PSCS2, "In Photoshop, files saved in the RGB mode typically uses a set of three 8 bit grayscale files..." [bold added for emphasis].
Where do you see him referring to Raw files in this context?
The grayscale files can form a color image because the three primary colors of the image are represented by the grayscale files. The raw file is also gray scale, but a color image can be formed from the red, blue and green elements of the Bayer array. In the latter case, all three primaries are encoded into one file rather than three separate files. If you can't see the analogy, I don't think you are very bright.
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The difference, and Jeff clearly stated this, is that the Raw is a single channel Grayscale file. In fact, this all goes back to me saying, "Raw is Grayscale data" which I continue to state and stand by.
That a single channel Grayscale file is different from a three channel Grayscale file shouldn't even have to be discussed here. Its a big Duh!
The fact that a Raw Grayscale file was produced with color filters, or that you can somehow split this data into now, three Grayscale files to represent a color image (something we know is the case, we've discussed demosicing), doesn't change the facts as I and Jeff and others have presented them. Yes, a Raw, Grayscale file HAS the potential to be a color image. Another big Duh moment. That doesn't make the single channel Grayscale Raw file a color file, cause it's not. ITS GRAYSCALE, something I said almost in passing, and something you said was debatable thus bringing on this entire sh*&-storm.
Lets cut to the chase. If a Raw file isn't Grayscale, are you saying its a color file?
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NO, my points are very relevant to the original post you made far too many posts ago:
You say the statement is debatable. We have a debate, one in which you haven't, as yet proven to me (and perhaps anyone else) that a Raw file has a color space. I say its essentially Grayscale, it has no color space. I stick to that opinion. You've quoted page 47 where it states "from camera color space" assuming that this is defined, I've mentioned several well qualified experts who say, its whatever you want to assign the scale of the primaries at encoding which I'll add is happening AT the state of demosaicing. You attempted to demonstrate this above, and so I again ask, what's the color space you made up? And how does this make it 'correct' and further prove that prior to this part of the process, the camera had a gamut?
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For the last time, what do you think of chapter 6 of the DNG specification?
You might also want to look at this thread on the [a href=\"http://www.adobeforums.com/webx?14@@.3bc2e802/2]Abobe Forums[/url]. Mr. Knoll put the camera color space in quotes, but he seems to be recognizing that it exists as per the DNG spec.
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Mr. Knoll put the camera color space in quotes, but he seems to be recognizing that it exists as per the DNG spec.
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Yes he puts it in quotes for exactly the reasons I've explained (well others have explained far better) in the numerous quotes above. Thomas puts them in quotes because he's saying as far as I'm concerned, that he agrees with the concepts expressed by both Phil and Richard which I don't think you've read. That basically, the color space is whatever anyone wants to say it is based on how they want to encode the data. Otherwise, both the DNG spec AND Thomas's quote would be far from vague, which clearly they are.
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Fine
Where do you see him referring to Raw files in this context?
The difference, and Jeff clearly stated this, is that the Raw is a single channel Grayscale file. In fact, this all goes back to me saying, "Raw is Grayscale data" which I continue to state and stand by.
That a single channel Grayscale file is different from a three channel Grayscale file shouldn't even have to be discussed here. Its a big Duh!
The fact that a Raw Grayscale file was produced with color filters, or that you can somehow split this data into now, three Grayscale files to represent a color image (something we know is the case, we've discussed demosicing), doesn't change the facts as I and Jeff and others have presented them. Yes, a Raw, Grayscale file HAS the potential to be a color image. Another big Duh moment. That doesn't make the single channel Grayscale Raw file a color file, cause it's not. ITS GRAYSCALE, something I said almost in passing, and something you said was debatable thus bringing on this entire sh*&-storm.
Lets cut to the chase. If a Raw file isn't Grayscale, are you saying its a color file?
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I agree that a raw file is gray scale. How many times do I have to state that? (So are the channels of an RGB file. Bruce has confirmed this, but you don't seem to get it.) However, if you understand the Bayer grid, you can extract the color information from a gray scale raw file. It is a special type of gray scale file.
Of course an RGB file in ProPhotoRGB contains no color. It merely has the data necessary to construct color when viewed with the proper software. The raw file contains no color, but it also has the information necessary to produce color
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I guess my assumption that you are not too bright is confirmed. I agree that a raw file is gray scale. How many times do I have to state that?
Just once, after you said this:
That statement is debatable. Look at the Adobe DNG Specifiation (http://www.adobe.com/products/dng/pdfs/dng_spec.pdf) on page 47 where mapping from the camera color space to the CIE XYZ space is discussed. The conversion is done with a three by three matrix, just like a conversion from sRGB to ProPhotoRGB is done. If you look at the source code of DCRaw you can review the actual matrix coefficients and conversion code.
Apparently the folks at Adobe think that the camera has a color space.
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In closing, here's the bottom line. We have a Raw file that I say is Grayscale. You read the DNG spec and say, based on what is said in the document, a Raw file is a color file because at some point, the Raw data is encoded into a color space. So, is a Raw file a color file or a Grayscale file? Not what it may become based on some processing, the damn file sitting on your flash card?
This seems (it is) all so simple.
I'll ignore your ill manners and comment at the top of this thread since I can feel your frustration at having to admit that you were barking up the wrong tree from the get go.
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Yes he puts it in quotes for exactly the reasons I've explained (well others have explained far better) in the numerous quotes above. Thomas puts them in quotes because he's saying as far as I'm concerned, that he agrees with the concepts expressed by both Phil and Richard which I don't think you've read. That basically, the color space is whatever anyone wants to say it is based on how they want to encode the data. Otherwise, both the DNG spec AND Thomas's quote would be far from vague, which clearly they are.
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You have addressed only one part of my post. Again, what do you think of Chapter 6 of the DNG specification? Make what you will of Mr. Knoll's quotes. You can't read his mind. Since you do not respond to reason, this is my last reply to you on this issue.
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Of course an RGB file in ProPhotoRGB contains no color. It merely has the data necessary to construct color when viewed with the proper software. The raw file contains no color, but it also has the information necessary to produce color
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And to go even deeper, its neither, its just a big pile of numbers.
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Again, what do you think of Chapter 6 of the DNG specification?
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I told you what I thought of chapter 6 of the DNG spec. As explained by Phil and Richard.
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I'll ignore your ill manners and comment at the top of this thread since I can feel your frustration at having to admit that you were barking up the wrong tree from the get go.
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Andrew,
I am sorry that my frustration affected my manners. Please accept my apology. Also, thank you for taking the high road and not replying in kind. I have edited my offending post. Just as in the Adobe forum postings on the same topic, agreement was not reached, and we will have to agree to disagree.
Bill
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For the last time, what do you think of chapter 6 of the DNG specification?
You might also want to look at this thread on the Abobe Forums (http://www.adobeforums.com/webx?14@@.3bc2e802/2). Mr. Knoll put the camera color space in quotes, but he seems to be recognizing that it exists as per the DNG spec.
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As it relates to DNG what I think is throwing you is that DNG ASSIGNS a color space based upon Thomas' testing of the spectral response of the sensor at D65 and Standard Illuminate A. Then based upon the white point in the metadata an arbitrary white point is assigned. Assigned mind you...and this is only on a DNG whose sensor has been decoded by Thomas and whose spectral properties have been measured.
Until Thomas MEASURES the the response and ASSIGNS a color space, there is no color space. Note that a DNG is a PROCESSED file, no longer a native raw file...
We are also hung up on the term "demosaicing"...well, the reason I pointed out the Wikipedia article is that my understanding of the term demosaicing is based upon that: "A demosaicing algorithm is a digital image process used to interpolate a complete image from the partial raw data received from the color-filtered image sensor (via a color filter array or CFA) internal to many digital cameras in form of a matrix of colored pixels."
So, splitting a single channel grayscale file into 3 grayscale files and combining them into a single RGB file is a "demosaicing algorithm" even if the process of assigning the red, green and blue pixels is manually done. Something, somewhere is saying, "ok, these pixels represent the red pixels, etc."
Taking the original raw, grayscale file and looking at it in any viewer app that does NOT designate which pixel are which colors and interpret those grayscale pixels as colors, will show the raw image as a single channel, grayscale file. Right? So, something, somewhere needs to do something to interpret the color of the Bayer Array, and I call that process a "Demosaicing" consistent with the definition on Wikipedia.
If you or Pannopeeper have a problem with that definition, I suggest you sign up on Wikipedia and do some updating of the article in question.
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Note that a DNG is a PROCESSED file, no longer a native raw file...
LOL, that does it for me.
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LOL, that does it for me.
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Do you dispute that DNG Converter processes the proprietary raw file into a DNG file? It's also what Camera Raw does when it opens a proprietary raw file...
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As it relates to DNG what I think is throwing you is that DNG ASSIGNS a color space based upon Thomas' testing of the spectral response of the sensor at D65 and Standard Illuminate A. Then based upon the white point in the metadata an arbitrary white point is assigned. Assigned mind you...and this is only on a DNG whose sensor has been decoded by Thomas and whose spectral properties have been measured.
Until Thomas MEASURES the the response and ASSIGNS a color space, there is no color space.
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Well, I thought that assigning a profile does not change the numbers in the file, but only determines how they are interpreted or what they represent. When Mr. Knoll measures the response of the camera at D65 he is determining the coefficients needed to perform a 3 by 3 matrix conversion from the "camera color space" to CIE XYZ or perhaps the PhotoProRGB chromaticity with a linear TRC. He is not creating a new space but merely describing the inherent properties of the sensor, i.e. the "native color space" of the camera . It is my thesis that those coefficients are implicit to the camera space. I don't know the details, but Mr. Knoll has stated that CIE XYZ has no white point. Perhaps you can help us in understanding the significance of this difference.
Furthermore, I don't think a white point is assigned at the time the DNG is created, but it can be interpolated from the D65 and Illuminate A profiles that are present in the DNG when needed. The AS SHOT white point is encoded in the raw file and can be used in this process.
Note that a DNG is a PROCESSED file, no longer a native raw file...
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Form the Adobe [a href=\"http://www.adobe.com/products/dng/pdfs/DNG_primer_manufacturers.pdf]DNG Primer for Manufacturers[/url] it is apparent that part of the DNG consists of metadata that the converter fills in describing the characteristics of the camera that are necessary for raw conversion.
The camera's actual image data are then "stored in a linear non-white balanced color space, usually the native color space of the camera". The data can be in mosaic form or demosaiced, but the mosaiced form is preferred, since it represents the original data captured by the camera.
In the preferred case, the actual image data are the same as in the raw file. If the file is demosaiced, then it is heavily processed and it would not be possible to apply a better demosaicing algorithm that might be developed in the future. Note that Adobe again mentions the native color space of the camera, which is not in accordance with your strict definition of a color space. As I initially stated, whether a raw file has a color space is debatable. Depending on one's definition, one can make either argument. However, I am not contending that this "native color space" can be used in Photoshop as one would use a printer profile. You discuss the pros and cons of camera profiling in your book, and make a good case that its absence in ACR is not a handicap.
We are also hung up on the term "demosaicing"...well, the reason I pointed out the Wikipedia article is that my understanding of the term demosaicing is based upon that: "A demosaicing algorithm is a digital image process used to interpolate a complete image from the partial raw data received from the color-filtered image sensor (via a color filter array or CFA) internal to many digital cameras in form of a matrix of colored pixels."
So, splitting a single channel grayscale file into 3 grayscale files and combining them into a single RGB file is a "demosaicing algorithm" even if the process of assigning the red, green and blue pixels is manually done. Something, somewhere is saying, "ok, these pixels represent the red pixels, etc."
Taking the original raw, grayscale file and looking at it in any viewer app that does NOT designate which pixel are which colors and interpret those grayscale pixels as colors, will show the raw image as a single channel, grayscale file. Right? So, something, somewhere needs to do something to interpret the color of the Bayer Array, and I call that process a "Demosaicing" consistent with the definition on Wikipedia.
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Strictly speaking the SPLIT_CFA command is demosaicing in the sense that it separates the red, blue and green components of the raw file into separate components. But it does no interpolation and does not fulfill the definition of demosaicing on Wikipedia. It does not attempt to determine the two primary colors that are absent in each Bayer array pixel. I can't speak for Panopeeper, but I have no quarrel with that definition.
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Strictly speaking the SPLIT_CFA command is demosaicing in the sense that it separates the red, blue and green components of the raw file into separate components. But it does no interpolation and does not fulfill the definition of demosaicing on Wikipedia. It does not attempt to determine the two primary colors that are absent in each Bayer array pixel. I can't speak for Panopeeper, but I have no quarrel with that definition.
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Uh huh...but putting the 3 split channels into a single 3 channel file (which is what you were talking about) DOES constitute a "CFA interpolation or color reconstruction"...the fact it does no resampling doesn't mean it ain't a "demosaicing algorithm", it just means it's not doing any upsampling. You take a single channel file, split it into 3 channels then combine them into an RGB file. I call that "demosaicing".
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Well, I thought that assigning a profile does not change the numbers in the file, but only determines how they are interpreted or what they represent. When Mr. Knoll measures the response of the camera at D65 he is determining the coefficients needed to perform a 3 by 3 matrix conversion from the "camera color space" to CIE XYZ or perhaps the PhotoProRGB chromaticity with a linear TRC. He is not creating a new space but merely describing the inherent properties of the sensor, i.e. the "native color space" of the camera . It is my thesis that those coefficients are implicit to the camera space. I don't know the details, but Mr. Knoll has stated that CIE XYZ has no white point. Perhaps you can help us in understanding the significance of this difference.
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Well, considering that camera sensors suffer from metameric failure at different spectral illuminates, (the whole reason Thomas tests the sensor at D65 AND Illuminate A), the spectral response of the camera's sensor is a sliding scale and thus would not have a single "color space" but potentially many "color spaces" depending on the illuminate.
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Uh huh...but putting the 3 split channels into a single 3 channel file (which is what you were talking about) DOES constitute a "CFA interpolation or color reconstruction"...the fact it does no resampling doesn't mean it ain't a "demosaicing algorithm", it just means it's not doing any upsampling. You take a single channel file, split it into 3 channels then combine them into an RGB file. I call that "demosaicing".
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You may call it demosaicing, but I don't think that the Wikipedia definition is met as there is no interpolation. Since, I have already conceded that by a strict definition, what I performed could be considered demosaicing, I don't know why you even brought up the subject other than to have the last word. Interpolation is making up values that did not exist. As you know, the Bayer array can capture only one color per pixel, and the other two colors are interpolated by best guess from surrounding pixels. My process did not invent any new data to "fill in the blanks" as Wikipedia states it, but merely looks at the same data in a different way.
Anyway, I don't see how this affects the argument that the raw file has no color space. If it has no space before the demosaicing, then it has no space after the demosaicing. What has changed that would make it a color space after demosaicing? The file may acquire characteristics to fulfill your definition of a color space later in the process.
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Anyway, I don't see how this affects the argument that the raw file has no color space. If it has no space before the demosaicing, then it has no space after the demosaicing. What has changed that would make it a color space after demosaicing? The file may acquire characteristics to fulfill your definition of a color space later in the process.
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It has no color space before because its not a color image, it has a color space after because someone has encoded the demoasiced data into a color space. That's exactly what encoding does.
[a href=\"http://www.color.org/ICC_white_paper_20_Digital_photography_color_management_basics.pdf]http://www.color.org/ICC_white_paper_20_Di...ment_basics.pdf[/url]
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Well, considering that camera sensors suffer from metameric failure at different spectral illuminates, (the whole reason Thomas tests the sensor at D65 AND Illuminate A), the spectral response of the camera's sensor is a sliding scale and thus would not have a single "color space" but potentially many "color spaces" depending on the illuminate.
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You are obsessing on white point, which is part of the ICC profile, but CIE XYZ lacks a white point and is widely considered to be a color space. Look at [a href=\"http://en.wikipedia.org/wiki/CIE_1931_color_space]Wikipedia[/url]. Is it a color space by your definition?
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You are obsessing on white point, which is part of the ICC profile, but CIE XYZ lacks a white point and is widely considered to be a color space. Look at Wikipedia (http://en.wikipedia.org/wiki/CIE_1931_color_space). Is it a color space by your definition?
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Yep...cause it has known and defined set of tristimulus values...a raw capture doesn't. The tristimulus values at D65 will be different than at Illuminate A (or presumed to be which is why Thomas tests cameras at both).
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It has no color space before because its not a color image, it has a color space after because someone has encoded the demoasiced data into a color space. That's exactly what encoding does.
http://www.color.org/ICC_white_paper_20_Di...ment_basics.pdf (http://www.color.org/ICC_white_paper_20_Digital_photography_color_management_basics.pdf)
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Your link does not work, so I can't comment. The demosaicing does not encode a color space, but merely separates out the color information from the Bayer array and fills in the missing information. As Jeff explains on pp 4-5 of his Camera Raw book, colorimetric interpretation, white balance, and tone mapping are separate steps and I think the encoding to which you refer takes place during these steps. As I stated, the demosaicing per se has no effect on whether the image has a color space or not. After the demosaicing, it is a color image by your definition, but apparently still lacks a color space.
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Yep...cause it has known and defined set of tristimulus values...a raw capture doesn't. The tristimulus values at D65 will be different than at Illuminate A (or presumed to be which is why Thomas tests cameras at both).
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Now we are expanding on the definition of a color space, and dropping the requirement of a white point. Hard to hit a moving target. BTW, illuminate is a verb. I think you mean illuminant.
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Now we are expanding on the definition of a color space, and dropping the requirement of a white point.
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Yep, it _IS_ hard to hit a moving target...and a sensor's response at D65 and Illuminant A means that a camera sensor DOESN'T have a fixed "color space".
Absolute color space: A color space in which colors are unambiguous, that is, where the interpretations of colors in the space are colorimetrically defined without reference to external factors.
Since the spectral response of a sensor depends on the illuminant (because of metameric failure) then a camera doesn't have an "Absolute color space". (there is another definition but I don't think it applies). Ref: [a href=\"http://en.wikipedia.org/wiki/Absolute_color_space]Absolute color space[/url]
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Your link does not work, so I can't comment.
The links on the ICC web page are kind of hosed, but the article discusses the role of color space encoding. I'll email them to fix this link.
The demosaicing does not encode a color space, but merely separates out the color information from the Bayer array and fills in the missing information.
After which, the color has to be encoded into a color space. IF you'd only read the posts made by Phil, and could get to the ICC link, you'd see this is a somewhat arbitrary process that someone has to define.
As Jeff explains on pp 4-5 of his Camera Raw book, colorimetric interpretation, white balance, and tone mapping are separate steps and I think the encoding to which you refer takes place during these steps.
They have to happen, at what step in the process, once we have a true color image that can have a color space may be questionable but at some point, the numbers have to have an associated scale placed on them. IT is at this point that these values have a color space. Prior to this, its Grayscale data (which you finally admit), it can't have a color space association.
As I stated, the demosaicing per se has no effect on whether the image has a color space or not. After the demosaicing, it is a color image by your definition, but apparently still lacks a color space.
No, at such a point, a color space is assigned if you want to use the term. Again, this is very clearly stated in the post I provided by Richard and Phil:
So usually what comes out of a camera or scanner is in an ordinary RGB
space that the engineers picked or defaulted to, and of course you can
profile to figure out what the primaries seem to be, what the gamut
limitations are, etc.
But then the numbers are usually matrixed to somebody's
standard RGB space, based on a set of primaries.
It again, is pretty simple. I don't know why you don't wish to accept this.
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very clearly stated in the post I provided by Richard and Phil:
It again, is pretty simple. I don't know why you don't wish to accept this.
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The posts by Rich and Phil were concerning the lack of a gamut for digital cameras. I'm not certain what I should have learned from their posts that affects the current discussion.
It was Panopepper who was confused on the issue of camera gamut. I was well aware of that issue, having made the same mistake some time previously in a different thread. It is easy to slip up, and even an expert like Peter Lange mentioned the gamut of a digital camera.
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The posts by Rich and Phil were concerning the lack of a gamut for digital cameras. I'm not certain what I should have learned from their posts that affects the current discussion.
I think its time to give up here.
You can't define a color gamut without a color space. They clearly indicate encoding of the data after a color file is produced using what you are calling demosaicing.
The original set of debates started because YOU questioned that a Raw file was Grayscale. Then you accepted it was Grayscale (because it is). A Grayscale file doesn't have a color space right? You can't define the boundaries of the primaries which is all a color space is. OK, we've got a color image now, we used demosaicing. So what's the color space? You keep going back to an article that doesn't define this to point out you feel Raw is a color image but we all know now, as you admit its not. Once we DO have a color file, what's the color space? Phil AND Rich have explained this.
Why do we keep going around in circles here?
The acceptance of yours that a digital camera has no color gamut AND that a Raw file has no color (nor color space) indicates to me we're at least making some progress. Again, read what Phil and Richard have written.
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Yep, it _IS_ hard to hit a moving target...and a sensor's response at D65 and Illuminant A means that a camera sensor DOESN'T have a fixed "color space".
Absolute color space: A color space in which colors are unambiguous, that is, where the interpretations of colors in the space are colorimetrically defined without reference to external factors.
Since the spectral response of a sensor depends on the illuminant (because of metameric failure) then a camera doesn't have an "Absolute color space". (there is another definition but I don't think it applies). Ref: Absolute color space (http://en.wikipedia.org/wiki/Absolute_color_space)
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Well, metameric failure occurs not only with printers, but also printers. The Epson 2000 was noted for prominent metameric failure. Yet people still made profiles for the printer.
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I think its time to give up here.
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Yes, I think so. You keep reiterating the same things and my responses also have become repetitious. Your ability to see another point of view is limited if it does not fit into your preconceived ideas, which are usually but not invariably correct.
You can't define a color gamut without a color space. They clearly indicate encoding of the data after a color file is produced using what you are calling demosaicing.
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First of all, we are not trying to define the color gamut of a camera, because it has none, as you have already pointed out. However, if you extended the analysis into the deep infra-red and ultra-violet a gamut would emerge.
The original set of debates started because YOU questioned that a Raw file was Grayscale. Then you accepted it was Grayscale (because it is).
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Your memory is rather selective and defective here. I did not deny that a raw file was gray scale, but I also pointed out that an RGB file is also gray scale as per Bruce Fraser's writings. Please refer back to post #11 in this thread. I have not changed my opinion. The raw file is gray scale because it records only luminance, not color.
The channels of an RGB file are gray scale for the same reason. The difference, which you don't seem able to grasp, is that both of them contain color information. Once we know what the channels of the RGB file represent, we can generate color. By the same token, once we know what the gray scale pixels in the Bayer array represent, we can also generate color. Demosiacing is not necessary to generate the color. It was Jeff who went off on that tangent.
A monochrome file can have a color space if it contains color information that, when properly decoded, defines colors.
Furthermore, I merely stated at the outset that raw files lack a color space is debatable, which this thread certainly has proved. To paraphrase Bill Clinton, who said, "it depends on what the meaning of IS is", it depends on what the definition of a color space is. I have yet to see your definition of what constitutes a color space; lacking this, we can go nowhere.
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Schewe has it spot on!
1. Noise comes from high ISO (sensor) long before the color space gets applied. A wider gamut simply stretchs it, but doesn't add to nor subtract from it. To cure noise, shoot at ISO 100 or maybe 200. At 400 or beyond, you are going to have to deal with the noise.
2. Sensors and RAW are LINEAR gamma, which is NOT how humans perceive things. That is why the linear data needs to be converted into a color space. Schewe pointed that out, but the significance is enormous.
3. If you choose a wide gamut, such as ProPhoto and edit in 16-bit, then there is "room" for gradations of color. If you don't EDIT a photo, color space doesn't mean much -- colors are what they are.
4. Lastly, RAW is 12 bit. If you edit in 8-bit, then you are throwing out some info (like rounding pennies to nearest dollar). If you are fussy about colors and detail (I am), then edit in 16-bit and print in high resolution. It makes a difference in skin color and details like hair. And if fine hair detail matters, then use a tripod so you aren't editing a 16-bit blur.
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> I have yet to see your definition of what constitutes a color space
"Color Space: A three-dimensional space or model into which the three attributes of a color can be represented, plotted, or recorded. These attributes are usually called hue, value, and chroma." "More commonly, color spaces are built on external references, such as the CIE system of measurement. "
Technically, a camera sensor is sensitive to some range of frequencies, which includes infra-red (and probably x-rays). The filters block certain frequencies and there are a set of grayscale numbers output which represent the data as seen through the red, green, and blue filters. Those data are linear (counting photons), which isn't useful until they are mapped into a well-defined color space, wherein the relationships among similar colors are handled consistently. It is then useful to convert from one color space to another, because every printer, monitor, etc. has a restricted range of what colors, saturation, and intensities/luminosity can be displayed. When you try to map a wide colorspace into a narrow one, then "out of gamut" colors are undefined. Convert your favorite photo to the smallest colorspace: one pencil and paper. Artists do it, but they make a lot of decisions about what gets left white (paper) and what gets a gray or black pencil. Even smaller: Adobe Photoshop "threshold" maps to black or white, no grays. The only decision is the cut-off point.
The camera color space is NOT well-defined without knowing the spectral response curves, etc. In these discussions. most people refer to well-defined color spaces: sRGB, Adobe RGB, LAB, ProPhoto .
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Interesting thread, not!! Exhausting and tedious and much more than I ever need or want to know now or never, ever. You guys all need to go out and drink some strong drinks, pinch some women and then come back, trashed, for the fifteenth round. Don King would not be proud of this excersize in mind bending, latent color space grappling caused by testoserone leakage directly into all of your brains. Stuff just like this is what caused his hair to stand up straight. Right about now I think Rodney is looking in the mirror and wondering what the hell happened.
My raw files have a color space...They are inside of a powerful button on my mouse. I click it and sparks fly, smoke churns out of my fan port and I'm glad the boys at the workshop figured it out for me cause I don't want to know anything more about it. I've got enough to keep me busy, what with my teenagers out drinking and racing stolen busses down Ashland Avenue.
Keep up the good work and don't buy tube socks at K-mart.
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Such discussions are useful because they remind us just how important definitions are. Many arguments can be resolved simply by getting an agreement on definitions. One you've got agreement on a satisfactory definition, it's then much easier to determine if the conditions of a particular scenario are consistent with the definition.
I could have interminable discussions with the Pope for example as to the definition of atheism, but I don't know much about color spaces .
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I want to give my contribution.
Some definitions:
- gamut = gamma, or range, of colors
- color space = a reference for values that fix a color
- color = human sensation
Generally color space and gamut term are used as synonyms. So let me do the same..
Camera try to imitate the human vision.
1. Humans has 3 cones (red, green, blue) sensitive to visibile light.
1.Cameras has 3 filters (red,green,blue) sensitive to visibile light (frequencies out of visibile are filtered out)
2. the stimuli are conveyed to the brain that process them, discount, more or less, the illuminant color and yields the color sensation
2. the stimuli and the white balalance info are recorded for raw processing (in camera or out of camera). But spectral response of camera sensor is not.
Now, can we speak of “human gamut” ?
Yes the colors humans can see were standardized from CIE in the far 1931, The well known horseshoe-shaped area in the CIE -xy chromaticity diagram is the human gamut.
Can we speak of “camera gamut” ?
I think so. Any camera has a gamma of colors that it can see. I think this gamut is similar to human gamut, as a camera try to imitate humans,
Are the info recorded in a raw file enough to produce a colored image?
The answer is no. Sensor spectral response is not recorded. So you have to know it from a different source.
Now. Is a raw file grayscale or colored?
Grayscale definition: a single value builded fusing color info with some algorithm. There is no way to rebuild original color from a grayscale value.
In a raw file you find red green and blue values.
Yes the raw is not ready for rendering until it is demosaiced and converted to some known color space. We can say that a raw must be processed to became a color image… but
A jpg file must be processed to became a color image.
A tif or png file is not ready for rendering until you know what the values mean (image color space). It must be processed to became a color image
So, in digital, every image file must be processed.
To discrimate grayscale file from colored file we have not to think if a process is needed to extract color, but we have to think if is possible to extract colors.
A grayscale file has no color info, so we can’t build colors.
A raw file has color info, so we can build colors.
Jacopo
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Schewe has it spot on!
1. Noise comes from high ISO (sensor) long before the color space gets applied. A wider gamut simply stretchs it, but doesn't add to nor subtract from it. To cure noise, shoot at ISO 100 or maybe 200. At 400 or beyond, you are going to have to deal with the noise.
The reason that I started this thread was that I was convinced that setting Prophoto in camera raw instead of Adobe rgb I could see more chroma noise and concluded that the wider colour space was the culprit Obviously I was wrong at least acording to Schew No offense meant Still I learned a lot more about colour spaces Some of it useful and some of it not!
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I want to give my contribution.
Some definitions:
- gamut = gamma, or range, of colors
Gamut isn't gamma if that's what your trying to say here. Gamut don't equal gamma either. Gamma is a simple mathematical formula.
- color space = a reference for values that fix a color
Fix a color?
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A monochrome file can have a color space if it contains color information that, when properly decoded, defines colors.
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This is all about using the proper language to discuss a technical topic.
Monochrome:
Monochrome \Mon"o*chrome\, n. [Gr. ? of one color; ? single + ?
color: cf. F. monochrome.]
A painting or drawing in a single color; a picture made with
a single color.
Well there's color, ONE.
Now looks look at color spaces of which you say a Raw file has (even tough you admit its a Grayscale file)
Color Space:
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components (e.g. RGB and CMYK are color models). However, a color model with no associated mapping function to an absolute color space is a more or less arbitrary color system with little connection to the requirements of any given application.
Further, its useful to read the work of Poynton (http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC7)
How is colour specified?
The CIE system defines how to map an SPD to a triple of numerical components that are the mathematical coordinates of colour space. Their function is analagous to coordinates on a map. Cartographers have different map projections for different functions: some map projections preserve areas, others show latitudes and longitudes as straight lines. No single map projection fills all the needs of map users. Similarly, no single colour system fills all of the needs of colour users.
The systems useful today for colour specification include CIE XYZ, CIE xyY, CIE L*u*v* and CIE L*a*b*. Numerical values of hue and saturation are not very useful for colour specification, for reasons to be discussed in section 36. (AR: nothing about monochrome as being color)
A colour specification system needs to be able to represent any colour with high precision. Since few colours are handled at a time, a specification system can be computationally complex. Any system for colour specification must be intimately related to the CIE specifications.
You can specify a single "spot" colour using a colour order system such as Munsell. Systems like Munsell come with swatch books to enable visual colour matches, and have documented methods of transforming between coordinates in the system and CIE values. Systems like Munsell are not useful for image data. You can specify an ink colour by specifying the proportions of standard (or secret) inks that can be mixed to make the colour. That's how PANTONE[tm] works. although widespread, it's proprietary. No translation to CIE is publicly available.
Do you see anything referring to monochrome, defining color?
You agree that a Raw file is Grayscale. What does Apple in its developer's guide have to say (http://developer.apple.com/dev/techsupport/insidemac/ACI/ACI-48.html):
Gray spaces typically have a single component, ranging from black to white, as shown in Figure 3-1. Gray spaces are used for black-and-white and grayscale display and printing.
Note that this piece refers to the ColorSync manager and how it handles different color spaces yet they define gray as gray spaces NOT gray color spaces for what should now be obvious reasons. They are very precise and careful in defying these spaces and when they use the term color:
gray spaces, used for grayscale display and printing
RGB-based color spaces, used mainly for displays and scanners
CMYK-based color spaces, used mainly for color printing device-independent color spaces, used mainly for color models named color spaces, used mainly for printing and graphic design
heterogeneous HiFi color spaces, also referred to as multichannel color spaces, primarily used in new printing processes involving the use of gold plate and silver, and also for spot coloring
Further (http://en.wikipedia.org/wiki/Monochrome):
For an image, the term monochrome is usually taken to mean the same as black-and-white or, more likely, grayscale, but may also be used to refer to other combinations containing only two colors, such as green-and-white or green-and-black. It may also refer to sepia or cyanotype images. In computing, monochrome has two meanings A monochrome computer display is able to display only a single color, often green, amber, red or white, and often also shades of that color.
In film photography, monochrome is the use of black and white film. In digital photography, monochrome is the capture of only shades of black by the sensor. Originally, all photography was done in monochrome until the invention of color film plates in the early 20th century.
Lastly, let me remind you and others of an old Chinese proverb: The first step towards genius is calling things by their proper name.
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Gamut isn't gamma if that's what your trying to say here. Gamut don't equal gamma either. Gamma is a simple mathematical formula.
You are trying to be scientific, I'm trying to be colloquial.
But you have to read well post. I said "gamma of colors", not "gamma".
My english is not so good, but I can try to explain "fix a color".
When you say that RGB values are (120,50,70) and you say that values are in sRGB color space, you are "fixing" what is the color you are referring to.
"setting" is more appropiate than "fixing" ?
Jacopo
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This is all about using the proper language to discuss a technical topic.
Monochrome:
Monochrome \Mon"o*chrome\, n. [Gr. ? of one color; ? single + ?
color: cf. F. monochrome.]
A painting or drawing in a single color; a picture made with
a single color.
Well there's color, ONE.
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By your definition, the raw file is not monochrome, because it has information for more than one color. The raw file has only luminance information. However, if we know that a certain luminance value is from a pixel overlain with a green filter, we know that it represents green luminance. The same applies to the other primaries. If we know the characteristics of the filters, then we can apply a 3 by 3 matrix transform to get the XYZ tristimulus values (Poynton discusses this). The XYZ space lacks a white value, but the raw file contains white balance information. Also we have a defined tone curve with a gamma of one. We have elements of a color space, depending on how a color space is defined. Unfortunately, you have yet to divulge your definition of a color space, so further debate is futile. Your tactic is to withhold your definition of a color space, and trickle out objections as needed as to why a given set of parameters is not a color space.
Jeff supplied a link on Wikipedia to absolute color spaces. This implies that all color spaces are not absolute. He seemed to imply that the camera space was not absolute, and hence not really a color space. This contradicts his own reference.
Reduced to absurdity, you can't get blood from a turnip, and you can't get color without color information, which may be explicit or implicit. Why don't you just give it up?
Your style of quotes is suboptimal. The first quote shows me as the source, but the others are anonymous and one can not judge their authority. Some are from Wikipedia and others are selected according to whether they support your view point or not.
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But you have to read well post. I said "gamma of colors", not "gamma".
My english is not so good, but I can try to explain "fix a color".
I think you may mean gamut, not gamma no? So you mean gamut of colors, not gamma of colors.
When you say that RGB values are (120,50,70) and you say that values are in sRGB color space, you are "fixing" what is the color you are referring to.
Ah OK I see. What I'd say is this is the scale of the numbers. That's what a color space defines.
R0/G255/B0 can be used to define the most saturated green numerically using a common set of numbers found in Photoshop to define color. But these are different colors in sRGB versus Adobe RGB (1998) because the scale of the numbers fall in different locations within human vision.
So, if I say my car gets 23 to the gallon, I'm missing a scale (miles or kilometers). Or if I say, the price of gas in my neighborhood is $3, I'm not suppling the scale (gallons or litters).
What a color space does is define the scale of the numbers. It think that's what you were referring to as "fix". One could say fixing a scale to the numbers, how's that?
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I think you may mean gamut, not gamma no? So you mean gamut of colors, not gamma of colors.
Ah OK I see. What I'd say is this is the scale of the numbers. That's what a color space defines.
R0/G255/B0 can be used to define the most saturated green numerically using a common set of numbers found in Photoshop to define color. But these are different colors in sRGB versus Adobe RGB (1998) because the scale of the numbers fall in different locations within human vision.
So, if I say my car gets 23 to the gallon, I'm missing a scale (miles or kilometers). Or if I say, the price of gas in my neighborhood is $3, I'm not suppling the scale (gallons or litters).
What a color space does is define the scale of the numbers. It think that's what you were referring to as "fix". One could say fixing a scale to the numbers, how's that?
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You understood perfectly now. Sorry for my english.
Jacopo
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By your definition, the raw file is not monochrome, because it has information for more than one color.
Nope, it doesn't contain color information, the entire point of this debate.
However, if we know that a certain luminance value is from a pixel overlain with a green filter, we know that it represents green luminance. The same applies to the other primaries.
We do?
If we know the characteristics of the filters, then we can apply a 3 by 3 matrix transform to get the XYZ tristimulus values (Poynton discusses this).
If. But again, you're still looking at this as what COULD be produced from the existing data, not what the existing data is.
A Raw file is no more a color image than a moth is a butterfly. Or an CMYK file is an RGB file just because we converted the color space. Lets stick to what the data is at a fixed point in time. As I said previously of course a Raw file will become a color file. But it isn't one yet.
Why don't you just give it up?
I probably should. But you get so close to 'getting it' by admitting that a Raw is a Grayscale file but then jumping to what it will be after a process and then saying its a colored image, I keep thinking you're getting close.
Your style of quotes is suboptimal. The first quote shows me as the source, but the others are anonymous and one can not judge their authority. Some are from Wikipedia and others are selected according to whether they support your view point or not.
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That so many sources dismiss your premise for one. The first was from Wikipedia as well as the one other. I provided you a source from Poynton and Apple. But if you're going to disagree with all the sources provided that dismiss your points because I failed to provide you a link, I think you're bottoming out here in making any kind of valid point.
Did anything I posted not fully describe the difference between a Grayscale, monochrome file and a color file? You said Raw was Grayscale (after starting all this by saying my post stating that Raw is Grayscale was incorrect) yes?
Yes or no, is a Raw file Grayscale data?
Yes or no, did anything I posted from the various sites agree that a Grayscale file is a color file?
Can you find anything other than a vague mention in the DNG spec that says a Raw (Grayscale file) is a color file which I submit it doesn't say? Not what it may be, what it is NOW?
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That so many sources dismiss your premise for one. The first was from Wikipedia as well as the one other. I provided you a source from Poynton and Apple. But if you're going to disagree with all the sources provided that dismiss your points because I failed to provide you a link, I think you're bottoming out here in making any kind of valid point.
Did anything I posted not fully describe the difference between a Grayscale, monochrome file and a color file? You said Raw was Grayscale (after starting all this by saying my post stating that Raw is Grayscale was incorrect) yes?
Can you find anything other than a vague mention in the DNG spec that says a Raw (Grayscale file) is a color file which I submit it doesn't say? Not what it may be, what it is NOW?
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Wishful thinking on your part that Wikipedia, Poynton, etc dismiss my points. I beg to differ. Whether a raw file is gray scale or not is semantics. It does contain tri-stimulus color information or we wouldn't get color. The DNG spec does not deal with these nit picking semantics (which are irrelevant to the discussion), but is hardly vague concerning mapping the Camera Color Space to the CIE XYZ space. It does not define a color space, but implicitly recognizes that the camera does have a space. Why argue any further, since this is very clear to anyone who does not apply Clintonian logic. Now, Bill Clintion is very smart, but you can't pin him down and he is very good at parsing a phrase. However, in the end he was impeached.
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Wishful thinking on your part that Wikipedia, Poynton, etc dismiss my points. I beg to differ.
You can do that, but you can't convince anyone else of your points if you continue to make this a religious not scientific discussion. As such, I will now say we are done here. If you want to believe that a Grayscale file is now a color file or that the earth was created in 6 days, despite carbon testing and sound science, or wish to dismiss the writings of Poynton and others, fine.
Whether a raw file is gray scale or not is semantics.
OK.
It does contain tri-stimulus color information or we wouldn't get color.
http://www.pmel.org/Color-Glossary.htm: (http://www.pmel.org/Color-Glossary.htm:)
CIE Tristimulus Values: Amounts (in percentages)O of the three components necessary in a three-color additive mixture required for matching a color: in the CIE System, they are designated as X, Y and Z. The illuminant and standard observer color matching functions used must be designated; if they are not the assumption is made that the values are for the 1931 CIE 2° Standard Observer and Illuminant C.
Once you have a color file, you can assume the color space which I've said over and over again (or it can be specified). And again, one can describe the moth that will become a butterfly, but until that process, its still a moth.
The DNG spec does not deal with these nit picking semantics (which are irrelevant to the discussion), but is hardly vague concerning mapping the Camera Color Space to the CIE XYZ space. It does not define a color space, but implicitly recognizes that the camera does have a space.
What camera color space? Where is this defined within the Raw which isn't in color?
And again, this happens when you actually HAVE a color file that does contain tristimulus color information. But you refuse to accept this so be it.
Why argue any further, since this is very clear to anyone who does not apply Clintonian logic. Now, Bill Clintion is very smart, but you can't pin him down and he is very good at parsing a phrase. However, in the end he was impeached.
Oh boy, you really are stretching here. Yup, I think its best we let this die. Go ahead, have the last word. You don't want to go down in LL forum history with that silly quote.
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Well, metameric failure occurs not only with printers, but also printers. The Epson 2000 was noted for prominent metameric failure. Yet people still made profiles for the printer.
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I was gonna let this one slide but then I remembered that the ONLY way to deal with the Epson 2000p was to make custom profiles for the Epson based upon the viewing light _BECAUSE_ of the metameric failure. In fact ProfileMaker was the first to put in the ability to make profiles based on the illuminant because inkjet inks at the time had metameric failure so bad. A profile made under tungsten sucked under daylight and vis versa. So, one single profile never worked well with that printer.
Which is also the reason that Thomas profiles a sensor at D65 and Standard Illuminate A and one of the reasons it can't be said that a camera has a fixed set of tristimulus values (spectral response) because the actual values depend on the spectral response, which will vary.